Spin Relaxation

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Spin relaxation refers to the process by which the spin angular momentum of particles, such as electrons or nuclei, returns to thermal equilibrium after being disturbed. This phenomenon is crucial in understanding magnetic resonance techniques and the dynamics of spin systems in various physical and chemical contexts.

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Key research themes

1. How can cavity quantum electrodynamics be employed to control and enhance spin relaxation rates in solid-state systems?

This research area focuses on leveraging the Purcell effect within high-quality microwave cavities to engineer spontaneous emission processes and thereby actively tune spin relaxation rates. By coupling spins to resonant electromagnetic modes, these works explore fundamental mechanisms of spin-photon interactions in solids and practical implications for initializing spin states and quantum information applications. Enhanced spin relaxation through cavity coupling challenges conventional assumptions regarding weak magnetic dipole-electromagnetic field coupling.

Controlling spin relaxation with a cavity

by D. Vion

2021, Nature

Key finding: By embedding donor spins in isotopically purified 28Si inside a high-Q superconducting microwave cavity, the authors reached a regime where spontaneous emission dominates spin relaxation, demonstrating a three orders of... Read more

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2. What are the microscopic mechanisms and theoretical frameworks governing spin relaxation and spin polarization in relativistic and strongly interacting spin-1/2 systems?

This theme encompasses semi-classical kinetic theories based on Wigner functions, relativistic hydrodynamics including spin degrees of freedom, and extensions to relaxation time approximations incorporating quantum spin transport coefficients. These frameworks model the dynamics of axial current densities, non-equilibrium corrections, and dissipative spin transport in relativistic matter, with relevance to high-energy physics contexts such as heavy-ion collisions where spin polarization phenomena have been experimentally observed.

Relativistic dissipative spin dynamics in the relaxation time approximation

by avdhesh kumar

2025, Physics Letters B

Key finding: The authors developed a relativistic semi-classical kinetic theory using Wigner functions in the relaxation time approximation (RTA) for spin-1/2 particles, deriving equations for axial-current densities consistent with... Read more

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Reexamination of the Elliott-Yafet spin-relaxation mechanism

by Hans Christian Schneider

2016

Key finding: This paper revisits the microscopic foundations of the Elliott-Yafet mechanism by rigorously deriving the spin dynamics including phonon-assisted electron spin-flip processes. It demonstrates that contributions from... Read more

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Weak nuclear spin singlet relaxation mechanisms revealed by experiment and computation

by Alexej Jerschow

2022

Key finding: Combining molecular dynamics simulations with ab initio computations, this study quantitatively accounts for experimentally observed nuclear spin singlet state relaxation rates in an organic molecule solution. It identifies... Read more

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3. How do structural properties, anisotropies, and nanoscale confinement influence spin relaxation phenomena in semiconductor nanostructures and porous materials?

The focus here is on the characterization and modeling of anisotropic spin relaxation mechanisms in low-dimensional semiconductor systems such as quantum wells, and in nanostructured materials containing nanopores or nanocavities. Research identifies how spin-orbit coupling terms (Rashba vs Dresselhaus), dipole-dipole interactions, structural nanoconfinement, and paramagnetic impurities modulate spin relaxation times, including spin-lattice and spin-spin relaxation. These studies combine experimental techniques (Hanle effect, NMR, ESR) with theoretical models of diffusion, dipolar coupling, and elastic interactions to extract nanoscale structural information from relaxation behavior.

Observation of Spin Relaxation Anisotropy in Semiconductor Quantum Wells

by Alexei Platonov and

2016

Key finding: By measuring three distinct spin relaxation times of two-dimensional electrons in asymmetrical (001) AlGaAs quantum wells via the Hanle effect, the work experimentally demonstrates anisotropy in the D'yakonov-Perel' spin... Read more

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Nuclear spin-lattice relaxation in nanofluids with paramagnetic impurities

by Grisha Furman

2024

Key finding: This study provides analytical expressions for nuclear spin-lattice relaxation times in liquids or gases confined within nanosized ellipsoidal cavities with paramagnetic impurities, considering ordered and isotropically... Read more

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Мulticomponents of Spin-Spin Relaxation, Anisotropy of the Echo Decay, and Nanoporous Sample Structure

by Vladimir Sokolovsky

2024

Key finding: Experimental and theoretical analysis of multicomponent 1H NMR echo decays in hydrogenated amorphous silicon films containing anisotropic nanopores reveals that the spin-spin relaxation time anisotropy arises from... Read more

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Temperature dependence of the NMR relaxation rate1/T1for quantum spin chains

by Sylvain Capponi

2022, Physical Review B

Key finding: Through finite temperature tensor network simulations, this work quantitatively traces the spin-lattice relaxation rate 1/T1 in spin-1/2 and spin-1 quantum chains across temperature regimes bridging the classical... Read more

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4. What advances in measurement techniques enable probing ultrafast spin-lattice and spin-spin relaxation processes inaccessible by conventional methods?

This theme reviews experimental innovations for accessing very short relaxation times (down to sub-microsecond or nanosecond regimes) essential for analyzing relaxation processes in materials with fast decoherence, such as glasses, doped polymers, or biological tissues. Techniques include microwave amplitude modulation in electron paramagnetic resonance (EPR), spin noise spectroscopy for real-time nonperturbative detection of nuclear spin relaxation, and adiabatic T1ρ mapping using ultrashort echo time MRI sequences like SWIFT that capture signals from fast relaxing spins. These methods extend dynamic range, improve sensitivity, and enable new insights into spin dynamics and tissue characterization.

Microwave Amplitude Modulation Technique to Measure Spin-Lattice (T1) and Spin-Spin (T2) Relaxation Times

by Sushil Misra

2021

Key finding: This work details a microwave amplitude modulation technique for measuring very fast electron spin-lattice relaxation times (10^-10 to 10^-6 s), overcoming limitations of traditional saturation/inversion recovery methods.... Read more

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Measurements of nuclear spin dynamics by spin-noise spectroscopy

by Gleb Kozlov

2021, Applied Physics Letters

Key finding: By utilizing spin noise spectroscopy with high finesse microcavities, the authors non-perturbatively monitor nuclear spin dynamics in n-GaAs in real time, tracking Overhauser fields via shifts in electron spin noise peaks.... Read more

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Capturing fast relaxing spins with SWIFT adiabatic rotating frame spin–lattice relaxation (T1ρ) mapping

by Michael Garwood

2024, NMR in Biomedicine

Key finding: This study introduces three-dimensional adiabatic T1ρ mapping by integrating magnetization-prepared sweep imaging with Fourier transformation (MP-SWIFT), enabling detection of spins with ultrashort transverse relaxation times... Read more

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All papers in Spin Relaxation

Backbone Dynamics ofEscherichia coliRibonuclease HI: Correlations with Structure and Function in an Active Enzyme

by Arthur Mandel

1995, Journal of Molecular Biology

Ribonuclease H is an endonuclease that hydrolyzes the RNA moiety of Department of Biochemistry and Molecular Biophysics RNA-DNA duplex molecules. Escherichia coli ribonuclease H is involved in Columbia University, 630 DNA replication, and... more

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Time-reversal symmetry breaking superconducting ground state in the doped Mott insulator on the honeycomb lattice

by Xiao-gang Wen and

We report the theoretical discovery of a novel time reversal symmetry breaking superconducting state in the t-J model on the honeycomb lattice, based on a recently developed variational method -the Grassmann tensor product state approach.... more

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Will Spin-Relaxation Times in Molecular Magnets Permit Quantum Information Processing?

by Alexei Tyryshkin

2007, Physical Review Letters

Using X-band pulsed electron-spin resonance, we report the intrinsic spin-lattice (T 1 ) and phasecoherence (T 2 ) relaxation times in molecular nanomagnets for the first time. In Cr 7 M heterometallic wheels, with M Ni and Mn,... more

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TROSY in triple-resonance experiments: New perspectives for sequential NMR assignment of large proteins

by Hans Senn

1998, Proceedings of the National Academy of Sciences

The NMR assignment of 13 C, 15 N-labeled proteins with the use of triple resonance experiments is limited to molecular weights below ϳ25,000 Daltons, mainly because of low sensitivity due to rapid transverse nuclear spin relaxation during... more

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Spin relaxation in semiconductor quantum dots

by Yuli Nazarov

2000, Physical Review B

We have studied the physical processes responsible for the spin-flip in GaAs quantum dots. We have calculated the rates for different mechanisms which are related to spin-orbit coupling and cause a spin-flip during the inelastic... more

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Highly Spin-Polarized Room-Temperature Tunnel Injector for Semiconductor Spintronics using MgO(100

by xin jiang

2005, Physical Review Letters

The spin polarization of current injected into GaAs from a CoFe=MgO100 tunnel injector is inferred from the electroluminescence polarization from GaAs=AlGaAs quantum well detectors. The polarization reaches 57% at 100 K and 47% at 290 K... more

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Observation of Metastable States in Spinor Bose-Einstein Condensates

by Ananth Chikkatur

1999, Physical Review Letters

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Spin Relaxation Quenching in Semiconductor Quantum Dots

by jbeli anouar

2001, Physical Review Letters

We have studied the spin dynamics in self-organized InAs͞GaAs quantum dots by time-resolved photoluminescence performed under strictly resonant excitation. At low temperature, we observe strictly no decay of both the linear and the... more

FIG. 1. (a) Time dependence of the PL components copolar- ized I* (A) and cross polarized I’ (V) to the o* polarized excitation laser (T = 10 K) and the corresponding linear po- larization Pj, (@). (b) Temperature dependence of the linear polarization dynamics. Inset: Pj, decay time 7 as a function of 1/(kpT).

FIG. 2. Time dependence of the PL components copolarized I* (A) and counterpolarized J~ (V) to the a* polarized exci- tation laser (T = 1.7 K) and the corresponding circular polar- ization Pc (@). Inset: schematic representation of the exciton pseudospin S rotating around the vector Q after a o* polarized excitation (see text).

FIG. 3. Magnetic field dependence of the circular (linear) po- larization under circularly polarized o* [(a),(d)] and linearly polarized a* [(b), (c)] excitations (T = 1.7 K). The displayec polarization values are the ones measured at any time delay after the pulsed excitation since we never observe any polar. ization decay. The solid lines are the best fits obtained with Eqs. (1a)-(1d): |g|/@ = 14.5 ps (see text).

which correspond, respectively, to the experiments pre- sented in Figs. 3(a)—3(d). Here, (A)* is defined as the statistical average of A* over the QD distribution (A = wo, O,); pe and PY, are fitting parameters which de- note, respectively, the circular and linear initial (¢ = 0) polarization.

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EPR and DNP Properties of Certain Novel Single Electron Contrast Agents Intended for Oximetric Imaging

by Klaes Golman

1998, Journal of Magnetic Resonance

Parameters of relevance to oximetry with Overhauser magnetic resonance imaging (OMRI) have been measured for three single electron contrast agents of the triphenylmethyl type. The single electron contrast agents are stable and water... more

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Muon-spin relaxation in AuFe and CuMn spin glasses

by Dale Harshman

1985, Physical Review B

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Electron spin relaxation times of phosphorus donors in silicon

by Alexei Tyryshkin

2003, Physical Review B

Pulsed electron paramagnetic resonance measurements of donor electron spins in natural phosphorus-doped silicon (Si:P) and isotopically-purified 28 Si:P show a strongly temperaturedependent longitudinal relaxation time, T 1 , due to an... more

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Weak antilocalization and spin precession in quantum wells

by Fedor Pikus

1996, Physical Review B

The results of magnetoconductivity measurements in GaInAs quantum wells are presented. The observed magnetoconductivity appears due to the quantum interference, which lead to the weak localization effect. It is established that the... more

T. is the inelastic scattering time. After the integration by E(g) in the right-hand side of Eq. (13) the result is expanded up to second order terms in series in small pa- rameters T9/Tp, VgTo, and N79, where v = OE/Ok. In the end, the following equation for the Cooperon is obtained: Here the Pauli matrices o act on the first pair of spin indices a,A, while the matrices p— on the second pair BN.

where |D| is the determinant of H (Eq. (35)) and |Dmm| are its minors of diagonal elements Dy», the sum in Eq. (32) can be immediately calculated’. According to Eqs. (28), (35), and (36), and Visa digamma-function. If both 2) = OY = 0 and only the cubic in k term with 03 is present, the expression Eq. (37) can be further reduced to the formula, which was obtained earlier in Ref. 6:

Note that, according to Ref. 15, the value of Ho is twice that used in Ref. 6. \ La, The case when 2) = +0”) and Q3 = 0 is a special one. In this case the operator Eq. (23) is diagonal in the basis of functions W,, if one uses coordinates x’ || (110) and y’ || (110):

FIG. 2. Energies determining the Dresselhaus spin split- ting as a function of electron density N;. Fermi energy Er and quadrupled mean kinetic energy 4Ez of the motion in the growth direction are shown by solid lines. Dotted line shows the difference 4Ez — Er that enters Eq. (38) for HO.

For all samples and for all carrier densities, the magne- toconductivity was a non-monotonic function of the mag- netic field. As we have mentioned before, presence of a minimum on the o(B) curves is a definite sign that the dominant spin-relaxation mechanism is the Dyakonov— Perel one. For the Elliott-Yafet mechanism in 2D struc- tures, the contribution of the singlet state with J = 0 is exactly canceled by one of the triplet states, namely the one with J = 1 and J, = 0, which is immediately evident from Eq. (42). Using Eq. (46) one can show that even for the highest density NV, = 2-102 cm~? and 7/72 = 4, the characteristic magnetic field Hey does not exceed 4-10-4 H;,, which is much smaller than Hgo. For the scattering on paramagnetic impurities, the negative mag- netoconductivity at lowest fields does not exist both in 2D and 3D systems.

FIG. 3. Experimental results (circles) and theoretical fits for the magnetoconductivity o(B) — o(0) for three dif ferent samples: a) — Al, b) — B1, and c) — C4. Solid lines show results of the theory outlined in Sec. II. Best fits ob- tained from Eqs. (37) and (39) are shown by dashed and dot- ted-dashed lines, respectively. Dotted vertical lines show the values B = 0.5Ht,, which limit the intervals of applicability of all three theories. The fitting parameters H as A oD Hso, and Hy, are given in Table IT.

where P = ifi/mo (S|pz|Z), P’ = ih/mo (S\|pz|Z’), and Q = th/mo (X|p,|Z") are the interband matrix elements, mo is the free electron mass, p = —ihV. Here we do not take into account the contribution into y and ag which In the 3-band k - p model one takes into account the states of the conduction band T; (Tg) with the Bloch function S, the valence band T'15, (Tg +P7) with func- tions X, Y, Z, and the higher band [15 ((g-+I'7-) with functions X’, Y’, and Z’. The energies of these states at k = 0 are: Er. = 0, Er, = —Ey, Er, = —(E, + A), Er,, = Ej, and Er,, = E+ A’. In this model mo/m, 7, and ag are given by the following expressions”? 48.7649;

FIG. 4. Characteristic magnetic fields as a function of the electron density Ns. a) — Density dependencies of the Dresselhaus (H oe) and Rashba (H OO) linear terms are shown by dotted and solid lines, respectively. Calculations were done according to Eq. 38 with y = 24 eVA® and ap = 7.3 A?. The values of these fields as obtained from best fit with the Sec. II theory are shown by squares (Rashba term) and circles (Dresselhaus term). b) — The Dresselhaus cubic term Hso — HY _ HY as a function of N,;. The lines are calculated using Eq. 38 for + = 24 eVA®. Solid line shows results for an isotropic scat- tering, 71/73 = 1, Dotted line — for 71/73 = 2.

TABLE I. Sample parameters: electron density Ns, mobil- ity ws, transport magnetic field Ht, (Eq. (38), and momentum relaxation time 71.

TABLE II. Parameters of the best fits for three samples Al, B1, and C4 (shown in Fig. 3 a), b), and c), respectively) as obtained from the theory of Sec. II (rows I), from the theory of Ref. 15 and Eq. 37 (rows II), and from the theory of Ref. 6 and Eq. 39 (rows IIT). All magnetic fields are in Gauss. ratio Ez/Er is calculated using Fig. 2. W (2) hen calculat- ing Hg6, we have assumed that the average field in the well is one half of the maximum field € = 47eN,/k. We have also taken into account the charge in the depletion layer No = 0.58-10!! cm~?. The value of ag was calcu- lated using Eq. (A1). If one takes into account the barri- ers, using theory of Refs. 26,27 and the sel calculated wave functions, the value of ag f-consistently will increase by about 60% for the electron densities in the interval N, = (1—2)-10!2 cm~?. This would increase the value of H ® approximately 2.5 times, but such of H % clearly do not agree with the expe large values riment. It is likely that the barrier contribution depends very strongly on their microscopic structure, which may be very differ- ent from the abrupt interface model, used i n the theory. It is also plausible that the different barrier structure is responsible for the relatively large value of sample C1, for which ap = 8.8 A. H 2 for the only small angle scattering is important (that is the case of scattering by the Coulomb potential) then 7/73 = 9 (see Eq. (11)). In our case we find 7,/73 to be in the range from 1 to 2. It is probably because scattering in our samples is the mixture of short and long range scattering. The short range scattering is probably due to alloy scattering that is known to be mobility limiting mechanism in GalnAs quantum wells. Long range scat- tering is most probably due to scattering on the ionized impurities in the 6-doped layer. Role of scattering by the charged impurities in the 6-doped layer was confirmed by observations of charge correlation effects (see Ref. 28).

TABLE III. Values of the parameters for GaAs and InAs calculated using the sp3s* model and the results of the k - 1 model. The parameters of k-p model were taken from Ref. 42, except those marked by asterisk, which were taken from Ref. 44. Parameters for Gao.s5Ino.15As were obtained by linear interpolation of the k - p model parameters between GaAs and InAs The values of y and ao as obtained in these models are also given. *The sign of Q in k- p model is not defined can be chosen to be sthe same as in sp3s* model.

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Subpicosecond spin relaxation dynamics of excitons and free carriers in GaAs quantum wells

by Luis Vina

1991, Physical review letters

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Optical pumping of a single hole spin in a quantum dot

by Khaled Karrai and

2008, Nature

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Transformation of spin information into large electrical signals using carbon nanotubes

by Gavin Burnell and

2007, Nature

Spin electronics (spintronics) exploits the magnetic nature of electrons, and this principle is commercially applied in, for example, the spin valves of disk-drive read heads. There is currently widespread interest in developing new types... more

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The electronic phase diagram of the LaO1-xFxFeAs superconductor

by Jochen Litterst

2009, Nature Materials

The competition of magnetic order and superconductivity is a key element in the physics of all unconventional superconductors, e.g. in high-transition-temperature cuprates 1, heavy fermions 2 and organic superconductors3. Here... more

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Optimal imaging parameters for fiber-orientation estimation in diffusion MRI

by Daniel Alexander

2005, NeuroImage

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Observation of extremely long spin relaxation times in an organic nanowire spin valve

by Supriyo Bandyopadhyay

2007, Nature Nanotechnology

We report spin valve behavior in an organic nanowire consisting of three layers -cobalt, Alq 3 and nickel -all nominally 50 nm in diameter. Based on the data, we conclude that the dominant spin relaxation mechanism in Alq 3 is the... more

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Waxholm Space: An image-based reference for coordinating mouse brain research

by Alexandra Badea

2010, Neuroimage

We describe an atlas of the C57BL/6 mouse brain based on MRI and conventional Nissl histology. Magnetic resonance microscopy was performed on a total of 14 specimens that were actively stained to enhance tissue contrast. Images were... more

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Low-temperature spin relaxation in n-type GaAs

by Kirill Kavokin

2002, Physical Review B

Low-temperature electron-spin relaxation is studied by the optical orientation method in bulk n-GaAs with donor concentrations from 10 14 cm Ϫ3 to 5ϫ10 17 cm Ϫ3 . A peculiarity related to the metal-to-insulator transition is observed in... more

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Optical Spin Hall Effect

by M. Glazov

2005, Physical Review Letters

A remarkable analogy is established between the well-known spin Hall effect and the polarization dependence of Rayleigh scattering of light in microcavities. This dependence results from the strong spin effect in elastic scattering of... more

FIG. 1 (color). (a) Scheme of the considered experimental configuration: linearly polarized light is incident on a semicon- ductor microcavity under oblique angle. Polarization of the scattered light is analyzed. (b) The red arrows show the distri- bution of the effective magnetic field induced by the TE-TM splitting on an elastic circle in reciprocal space. (c) The green circle sketches the polariton state resonantly excited by a pulse having an in-plane wave vector along the x axis. This initial polariton state is TM polarized and has its pseudospin parallel to the x direction (green arrow). The blue circles and blue arrows show the short-time distribution of particles and their pseudospin orientation. The red arrows show the distribution of the effective magnetic field induced by the TE-TM splitting.

FIG. 2 (color). The black arrows show the polariton pseudo- spin orientation in the reciprocal space at a time t = 36 after ar- rival of the TM-polarized excitation pulse. In the first and third quarter (emission angles [0°-—90°] and [180°—270°], respec- tively) polaritons have their pseudospins parallel to the z direc- tion, which corresponds to the right-circularly polarized emis- sion (a* ), shown in red. In the second and fourth quarter (emis- sion angles [90° —180°] and [270° —360°], respectively) the po- lariton pseudospins are antiparallel to the z axis, which corre- sponds to the left-circularly polarized emission (a ), shown in blue. where the first term describes precession and the second term describes the flux of polaritons coming from the initial state. It has only the x component (or the y compo-

FIG. 3. (a) Dispersion of the LPB in the model microcavity. The bare exciton energy is 1450 meV, and the bare photon energy at k = 0 is 1439 meV. (b) Wave-vector dependence of the energy splitting Q between TE- and TM-polarized polariton modes. (c) Wave-vector dependence of the product 0.7, where 7 is the polariton radiative lifetime.

FIG. 4. (a) Time dependence of the circular polarization de- gree of light emitted by the states whose in-plane wave vector makes an angle 6 of +45° (solid line) and —45° (dashed line) with respect to the wave vector of the incident light. The inset shows the time dependence of the populations of the correspond- ing states. (b) Integrated circular polarization degree versus the scattering angle 6 for two different in-plane wave vectors of the incident light, namely, 2.6 X 10° m~! (solid line) and 1.3 X 10° m7! (dashed line).

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Stimulated and Spontaneous Optical Generation of Electron Spin Coherence in Charged GaAs Quantum Dots

by L. Sham

2005, Physical Review Letters

We report on the coherent optical excitation of electron spin polarization in the ground state of charged GaAs quantum dots via an intermediate charged exciton (trion) state. Coherent optical fields are used for the creation and detection... more

FIG. 1: (a) Magnetic field (B) orientation with respect to QD. (b) Excitation picture for the charged QD in the Voigt geometry (6 = 0°), with ground states |v+) denoting elec- tron spin projections +4 along the z-axis split by fiw.. The trion states |t-+) are labeled by the heavy-hole angular mo- mentum projection +3 along the z-axis. Solid (dashed) lines denote transitions excited by ¢* (a7) light. (c) Schematic of differential transmission (DT) experimental setup. We report on the coherent optical excitation of electron spin polarization in the ground state o charged GaAs quantum dots via an intermediate charged exciton (trion) state. Coherent optica fields are used for the creation and detection of the Raman spin coherence between the spin grounc states of the charged quantum dot. The measured spin decoherence time, which is likely limitec by the nature of the spin ensemble, approaches 10 ns at zero field. We also show that the Ramar spin coherence in the quantum beats is caused not only by the usual stimulated Raman interactior but also by simultaneous spontaneous radiative decay of either excited trion state to a coheren combination of the two spin states.

FIG. 2: (a) DT spectrum with the pulse delay fixed at +10 ps. The shaded region is the pulse spectrum, and the arrows at T (X) label the trion (exciton) resonances. (b) Variation of the decay rate and the oscillation frequency with the field. We extract the g-factor to be |ge,2| = 0.13. (c) DT signal at X for Bz = 6.6 T showing no oscillations. Inset: Single QD exciton QBs obtained in the Faraday geometry with B, = 0.9 T [16]. (d) Spin QBs in DT signal as a function of in-plane magnetic field B,, obtained when the laser pulse is tuned to selectively excite the T resonance. Data shown in (c) and (d) are the differences between PCP and OCP signals. Solid lines show fits to the data using Eq. @).

FIG. 3: (a) and (b) show the changes in the amplitude (A2) and phase (@) of the oscillations as a function of splitting. Solid (dashed) lines denote theoretical predictions for these parameters with (without) the effects of SGC. In numeri- cal calculations, the optical pulses are assumed Gaussian; i.e. T(w) = exp(—w?/207) (o = 0.35 meV). verified that the dependence is not due to shifts in the trion resonance, or changes in the oscillator strength with magnetic field. As elaborated below, the data in Fig. B] provides experimental confirmation for SGC.

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Muon Spin Relaxation Studies of Zn-Substitution Effects in High- Tc Cuprate Superconductors

by B. Nachumi

1996, Physical Review Letters

We have performed transverse-field muon spin relaxation measurements of the Zn-substituted cuprate high-T c superconductors: La 22x Sr x ͑Cu 12y Zn y ͒O 4 and YBa 2 ͑Cu 12y Zn y ͒ 3 O 6.63 . The superconducting carrier density͞effective... more

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Electron spin evolution induced by interaction with nuclei in a quantum dot

by Leonid Glazman

2003, Physical Review B

We study the decoherence of a single electron spin in an isolated quantum dot induced by hyperfine interaction with nuclei for times smaller than the nuclear spin relaxation time. The decay is caused by the spatial variation of the... more

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Spin-Orbit-Mediated Spin Relaxation in Graphene

by Daniel Huerta

2009, Physical Review Letters

We investigate how spins relax in intrinsic graphene. The spin-orbit coupling arises from the band structure and is enhanced by ripples. The orbital motion is influenced by scattering centers and ripple-induced gauge fields. Spin... more

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Evidence for Time-Reversal Symmetry Breaking in the Noncentrosymmetric Superconductor LaNiC2

by Jorge Quintanilla

2009, Physical Review Letters

Muon spin relaxation experiments on the noncentrosymmetric intermetallic superconductor LaNiC 2 are reported. We find that the onset of superconductivity coincides with the appearance of spontaneous magnetic fields, implying that in the... more

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Quantification of Regional Intrapulmonary Oxygen Partial Pressure Evolution during Apnea by 3He MRI

by Anselm Deninger

1999, Journal of Magnetic Resonance

We present a new method to determine in vivo the temporal evolution of intrapulmonary oxygen concentrations by functional lung imaging with hyperpolarized 3 Helium (3 He 3). Single-breath, single-bolus visualization of 3 He 3 administered... more

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Direct Observation of the Electron Spin Relaxation Induced by Nuclei in Quantum Dots

by T. Amand

2005, Physical Review Letters

We have studied the electron spin relaxation in semiconductor InAs=GaAs quantum dots by timeresolved optical spectroscopy. The average spin polarization of the electrons in an ensemble of p-doped quantum dots decays down to 1=3 of its... more

FIG. 1. (a) cw photoluminescence spectrum of the QD. (b) Circular polarization of the QD ground state luminescence for (@) B, = 0 and (A) B, = 100 mT. (c) Scheme of a posi- tively charged exciton X* formed by a spin polarized electron and two holes with opposite angular momentum projection. Figure 1(a) displays the cw PL spectrum of the QD ground states at T = 10K. It is characterized by a ful width at half maximum of about 50 meV due to the fluctuations of size, shape, and strain in the ensemble of dots. Figure 1(b) presents the circular polarization of the time-integrated PL after a circularly polarized picosecond excitation. The excitation energy is 1.44 eV; this corre- sponds to the photons absorption in the low energy par of the WL (because of the strain and the quantum confine- ment, this absorption corresponds to a heavy-hole-to- electron-like transition [18]). We measure a circular polar- ization degree of ~19% of the QD ground state emission (B, = 0). The excitation intensity is about 1 mW; this corresponds to the photogeneration of less than one electron-hole pair per QD. All three p-doped samples

FIG. 2. Circular polarization dynamics of the QD lumi- nescence after a circularly polarized o+ laser excitation. Inset: Photoluminescence intensity copolarized J* and counter- polarized 7~ with the laser (semilogarithmic scale). The detec- tion energy is centered at Fy,, = 1.11 eV.

FIG. 3. Circular polarization dynamics of the QD ground state luminescence (semilogarithmic scale) for B, = 0, B, = 100 mT, and B, = 400 mT. The inset displays the calculated time de- pendence of the average electron spin (S(t))/So (see text). A key argument for the hyperfine interaction being responsible for the initial polarization decay comes from magnetic field dependent measurements. We have re- corded the circular polarization dynamics of the QD

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Ferroelectric Control of Spin Polarization

by Florian Kronast

2010, Science

A current drawback of spintronics is the large power that is usually required for magnetic writing, in contrast with nanoelectronics, which relies on "zero-current," gate-controlled operations. Efforts have been made to control the... more

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Electrical Control of Spin Relaxation in a Quantum Dot

by Micah Hanson

2008, Physical Review Letters

We demonstrate electrical control of the spin relaxation time T1 between Zeeman split spin states of a single electron in a lateral quantum dot. We find that relaxation is mediated by the spinorbit interaction, and by manipulating the... more

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Giant spin relaxation anisotropy in zinc-blende heterostructures

by N. Averkiev

1999, Physical Review B

Spin relaxation in-plane anisotropy is predicted for heterostructures based on zinc-blende semiconductors. It is shown that it manifests itself especially brightly if the two spin relaxation mechanisms (D'yakonov-Perel' and Rashba) are... more

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On the application of ultra-fast rare experiments

by Dieter Leibfritz

1992, Magnetic Resonance in Medicine

The ultra-fast application of the RARE experiment is described in detail, with special emphasis on its multifarious applications with preparation experiments that produce transverse magnetization. The factors affecting the temporal... more

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Spin tunneling and phonon-assisted relaxation in Mn12-acetate

by Michael Leuenberger

2000, Physical Review B

We present a comprehensive theory of the magnetization relaxation in a Mn12-acetate crystal in the high-temperature regime (T>1 K), which is based on phonon-assisted spin tunneling induced by quartic magnetic anisotropy and weak... more

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Dynamics connect substrate recognition to catalysis in protein kinase A

by Larry R . Masterson and

2010, Nature Chemical …

Atomic resolution studies of protein kinases have traditionally been carried out in the inhibitory state, limiting our current knowledge on the mechanisms of substrate recognition and catalysis. Using NMR, X-ray crystallography and... more

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Knight shifts and nuclear-spin-relaxation rates for two-dimensional models of CuO2

by N. Bickers

1990, Physical review. B, Condensed matter

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Determination of cortical bone porosity and pore size distribution using a low field pulsed NMR approach

by Qingwen Ni and

2003, Journal of Orthopaedic Research

The objective of this study was first to prove the concept of a low field pulsed nuclear magnetic resonance (NMR) process for assessing the cortical porosity and pore size distribution of human bone in vitro, and then to apply the... more

Fig. 2. Comparison of typical spectra of the 7, distribution of NMR measurements and the pore size distribution obtained by bone histo- morphometry. Fig. 1. Histomorphometry determination of the porosity and pore size distribution in bone: (A) is a 200x photographic image of a bone cross section, (B) is the image after process used to measure lacunae porosity; (C) is a 50x photographic image of a bone cross-section, and (D) is th processed image used to estimate the Haversian canal porosity.

Fig. 3. Correlation between porosity values obtained by NMR and histomorphometry approaches.

Fig. 4. Age-related changes in the Haversian porosity and lacunae porosity determined by both the NMR approach and bone histo- morphometry.

Fig. 5. Conceptual representation of NMR approaches to determine the porosity of porous media.

Fig. 6. Example plot of fit errors 2 (upper) and A, (lower) as a functior of 6. For each value of 6, a unique solution for f(7>) exists. In this study the method proposed by Fordham et al. [6] was used to choose the appropriate level of smoothing, using an optimum 6 (d9,:). To do so, an optimal regu- larization parameter called ‘“‘slop tolerance” or “slop” will be introduced. A simple method relating 6,,; to the

Pop,—porosity calculated under peak P,; Pop,—porosity calculated under peak P2; Pop,—porosity calculated under peak P3; Ponmr—overal porosity determined by NMR; P’onmr—modified overall porosity determined by NMR; Pojacunae—Porosity by osteocytic lacunae; Poyaver—porosity by Haversian canals; Popisto—overall porosity determined by histomorphometry. Paired-tests indicate that no significant differences (p > 0.05) exis: between Pop, (%) and Potacunae (%), Pop, (%) and PoHaver (%), and Ponmre (%) and Poxisto (%), respectively. Comparison of NMR and histomorphometry measurements Table 1

Tsp, —median T> time of peak P;; T>p,—median 7) time of peak Ps; diacunae—median nominal diameter of osteocytic lacunae; dHaversian—media nominal diameter of Haversian canals; Pjacunae—Surface relaxivity of lacunae; Pyavyersian—Surface relaxivity of Haversian canals. Determination of the surface relaxivity of bone samples

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Observation of extremely slow hole spin relaxation in self-assembled quantum dots

by Dominik Heiss

2007, Physical Review B

We report the measurement of extremely slow hole spin relaxation dynamics in small ensembles of self-assembled InGaAs quantum dots. Individual spin orientated holes are optically created in the lowest orbital state of each dot and read... more

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Hybrid plasmonic magnetic nanoparticles as molecular specific agents for MRI/optical imaging and photothermal therapy of cancer cells

by Jesse Aaron

2007, Nanotechnology

Nanoparticles which consist of a plasmonic layer and an iron oxide moiety could provide a promising platform for development of multimodal imaging and therapy approaches in future medicine. However, the feasibility of this platform has... more

Figure 1. (a) TEM image of magnetic gold nanoparticle solution. The scale bar is approximately 100 nm. (b) Absorbance spectra of nanoparticles before (blue) and after (red) conjugation with antibodies.

Figure 3. MRI imaging of cells labelled with hybrid nanoparticles. Sections (a)-(f) correspond to the following cell suspensions through the entire figure: (a) labelled, 1.4 x 107 cells ml~!; (b) labelled, 7 x 10° cells ml~!; (c) labelled, 3.5 x 10° cells mI~!; (d) labelled, 1.75 x 10° cells mI~!; (e) unlabelled, 1.4 x 10’ cells ml~!; (f) labelled, 1.4 x 107 cells ml~!. (A) Dark-field reflectance images of aliquots taken from each cell/collagen solution; (B) colour image of NMR tubes loaded with tissue phantoms; (C) 7>-weighted image of the tubes shown in (B); (D) 7;-weighted image of the tubes shown in (B). The scale bar is approximately 50 jxm in the dark-field images. We conducted preliminary calculations to estimate the range of the hybrid contrast agents and cellular concentrations that will be detectable using MRI. We defined the criterion for minimum detection to be that contrast-enhanced tissue compartments must exhibit a net change in signal level that exceeds three times the standard deviation of noise characteristics associated with its baseline intensity. This condition may be equivalently expressed as a minimal contrast- to-noise ratio (CNR) of 3. The minimum detection threshold was calculated in terms of cells per voxel as a function of the initial signal-to-noise (SNR) ratio of the image (figure 4). The yellow line in figure 4 depicts the limit below which the either unlabelled cells or different concentrations of cells labelled with antibody-conjugated magnetic gold nanoparticles as shown in figure 3(B). The concentration of labelled cells was varied from 1.75 x 10° to 1.4 x 107 cells ml~'. The dark-field reflectance images in figure 3(A) correspond to small aliquots of solution taken from each of the suspensions of cells in the MRI tubes (figure 3(B)). Labelled cells appear orange-yellow and unlabelled cells exhibit characteristic endogenous blue scattering in the dark-field imaging (figure 3(A)). The labelled cells show a strong negative contrast in 7, which decreases with decrease in cell density (figure 3(C)). Unlabelled cells are indistinguishable from pure collagen, and no significant T; effects were observed in any cell sample.

Figure 2. Optical imaging with hybrid nanoparticles. Reflectance confocal ((a), (b)) and dark-field reflectance ((c), (d)) images of unlabelled cells ((a), (c)) and cells labelled with anti-EGFR hybrid nanoparticles ((b), (d)). Confocal images were obtained using 594 nm excitation and a 20x objective. Dark-field imaging was carried out using a 20x dark-field objective and 75 W Xe illumination. Scale bars are approximately 30 jm.

Figure 4. Theoretical detection limit for cells labelled with magnetic gold nanoparticles.

Figure 5. Photothermal therapy with anti-EGFR hybrid nanoparticles. (a) Absorbance spectra of unlabelled cells in the presence of PEGylated hybrid nanoparticles (green) and of labelled cells (red). The total amount of nanoparticles is the same in both cell suspensions. Fluorescence images of cells labelled with anti-EGFR hybrid nanoparticles (b) and cells pre-exposed to PEG-coated particles (c) after one 7 ns, 400 mJ cm7? laser pulse at 700 nm. Green fluorescence is due to calcein AM live stain that indicates cellular survival. (d) Dark-field reflectance image of the irradiated labelled cells at the boundary of the laser beam spot; the green colour of cells which are located outside of the laser beam is associated with fluorescence of the live-cell stain. (e) Fluorescence image of cells pre-exposed to PEG-coated hybrid nanoparticles after six hundred 7 ns, 400 mJ cm~? pulses at 700 nm. Fluorescence images were obtained using a 10x objective and a 475 nm/510 nm excitation/emission filter cube and the dark-field imaging was carried out with 20x dark-field objective and a Xe lamp illumination. The scale bars are approximately 100 jm in fluorescence images and approximately 50 zm in the dark-field image.

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Systematic variation of magnetic-field penetration depth in high-Tc superconductors studied by muon-spin relaxation

by David Opie

1988, Physical Review B

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Resolution enhancement in single-shot imaging using simultaneous acquisition of spatial harmonics (SMASH)

by James Goldfarb

1999, Magnetic Resonance in Medicine

Spatial resolution in single-shot imaging is limited by signal attenuation due to relaxation of transverse magnetization. This effect can be reduced by minimizing acquisition times through the use of short interecho spacings. However, the... more

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Fractal Form of Proteins

by Douglas Stinson

Physical Review Letters

Electron spin relaxation measurements on low-spin Fe3 in several proteins show that they occupy a space of fractal dimensionality d = 1.65+ 0.04, in conformity with the dimensionality d = y of a self-avoiding random walk. Analysis of... more

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Low-temperature spin freezing in the Dy2Ti2O7 spin ice

by B. Ueland

2004, Physical Review B

We report a study of the low temperature bulk magnetic properties of the spin ice compound Dy 2 Ti 2 O 7 with particular attention to the (T < 4 K) spin freezing transition.

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Longitudinal 1 H Relaxation Optimization in TROSY NMR Spectroscopy

by Beat Vögeli

2002, Journal of the American Chemical Society

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Hydration and internal properties of polyelectrolyte multilayers

by Monika Schönhoff and

2007, Colloids and Surfaces A: Physicochemical and Engineering Aspects

In this review we summarize novel aspects of the hydration and internal properties of polyelectrolyte multilayers formed by layer-by-layer assembly. Reflectivity techniques monitor the water content and swelling behavior, while spin... more

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Ab initio treatment of noncollinear magnets with the full-potential linearized augmented plane wave method

by S. Blügel

2004, Physical Review B

The massively parallelized full-potential linearized augmented plane-wave bulk and film program FLEUR for first-principles calculations in the context of density functional theory was adapted to allow calculations of materials with... more

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Multicomponent T 2 relaxation analysis in cartilage

by Ping-Chang Lin

2009, Magnetic Resonance in Medicine

MR techniques are sensitive to the early stages of osteoarthritis, characterized by disruption of collagen and loss of proteoglycan (PG), but are of limited specificity. Here, water compartments in normal and trypsin-degraded bovine nasal... more

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Spin coupling and relaxation inside molecule–metal contacts

by Roberto Rojas Robles

2011, Nature Communications

Advances in molecular electronics depend on the ability to control the charge and spin of single molecules at the interface with a metal. Here we show that bonding of metal-organic complexes to a metallic substrate induces the formation... more

Figure 1 | Structure and electronic properties of paramagnetic CuPc and diamagnetic NiPc adsorbed on Ag(100). (a) STM image of single CuPc (top, 1=72 pA, V,= -5mV) and NiPc (bottom, /=100 pA, V,= -3 mV), image size 2.5nmx2.5nm. The diagram superposed to NiPc indicates the position of the metal (orange), C (grey), N (blue), and H (white) atoms. (b) d//dV spectra of CuPc (top) and NiPc (bottom) around E, measured on benzene (blue dot) and (¢) on Cu and Ni ions (red dot) (setpoint: /=2nA/1.1nA, V,= -—100 mV for CuPc/NiPc). Labels denote Kondo resonances of different nature: zero- bias (K), triplet-singlet (K,,), and vibrational (K,). Black solid lines in ¢ are fits to the data using the sum of Lorentzian (blue) and step functions (shaded). (d) d?I/dV’ spectra of CuPc (top) and NiPc (bottom) measured on Cu and Ni ions. The dashed lines indicate the energy of the step excitations in ¢, which correspond to the amplitude of the Raman-active vibrational modes of gas-phase CuPc (bars)?!. (e) Extended di/dV spectra of CuPc on benzene and (f) Ci sites (setpoint: /=3nA, V,= -—2\V). (g) dl/dV maps of the molecular orbitals and inelastic vibrational signal shown in e and f together with the d7//dV? mar of the Kondo resonance. The intensity in each map is scaled independently for maximum contrast.

Figure 2 | Triplet-singlet excitations and temperature dependence of the CuPc Kondo resonance. (a) d//dV spectrum measured at 4.8 K and fit of the zero-bias intensity and triplet-singlet side peaks (setpoint: /=2nA, V,= -—100 mV). (b) Intensity (G) of the zero-bias and triplet-singlet conductance peaks as a function of temperature normalized by the conductance measured at 4.8K (G,). The solid (dashed) line is a fit of G/Gp for the S=1/2 (underscreened S=1) Kondo model obtained within the numerical renormalization group approach’, with T,= 27K. (¢€) Temperature dependence of the zero-bias and triplet-singlet resonance widths I, (filled symbols) and I, (open symbols), respectively. The solid line is a fit of I, according to ref. 20, resulting in T,=27K.

Figure 3 | Projected density of states (PDOS) and intramolecular exchange coupling. (a) PDOS of CuPc and NiPc on Ag(100) calculated by DFT. The projection onto the different molecular orbitals is given by solid lines; shaded areas indicate the metal d-character of each state. (b) Spin density of neutral and anionic CuPc and NiPc species in the gas-phase. The sign of the spin is indicated in red/green. On the other hand, the intensity of the triplet-singlet excitations is proportional to the local spin/charge density as well as to the prob- ability to tunnel to spin-polarized orbitals, the latter being much higher for the LUMO. Thus, as the STM tip has the role of a mobile electrode, our measurements show that the appearance of nonlin- ear resonances in the I/V curves of metal-organic complexes is

Figure 4 | Influence of intermolecular interactions. (a) and (b) STM image of a 3x3 cluster of CuPc before and after removing a corner molecule by manipulation with the tip. (¢) and (d) Kondo resonances simultaneously mapped with the images in a and b. Note that the Kondo resonance can be observed only for molecules with a number of lateral bonds smaller than three. (e-h) Molecular orbital conductance maps show the correlation between molecular coordination, energy shift of the LUMO, and disappearance of the Kondo effect. (i) Conductance spectra acquired at 4.8 K at the benzene ring of molecules with different number of side-to-side neighbours and in different configurations. (j) Evolution of the Kondo temperature with the number of intermolecular bonds.

Figure 5 | Site-specific conductance of spin and vibrational co-tunnelling processes. (a) Schematic of the cotunnelling mechanisms giving rise to zero-bias, vibrational, and triplet-singlet Kondo resonances. (b) Intramolecular conductance: d//dV spectra measured along a line crossing the Cu ion and a benzene ring (horizontal axis) as a function of V, (vertical axis) (stabilization setpoint: /=1nA, V,= -100 mV). Red-coloured regions illustrate the different localization of the Kondo excitation channels. Note the abrupt transition from vibrational to triplet-singlet excitations at ~4 A away from the Cu site.

Figure 6 | Spin versus vibrational relaxation channels. (a) Diagram showing the spin distribution and couplings of CuPc induced by adsorption on Ag. (b) Normalized width I'/T), of the inelastic Kondo resonances as a function of V,/k,T,. Data for CuPc and NiPc are compared with that for other molecules for which either spin or vibrational Kondo excitations have been separately reported. Triplet-singlet (cyan) and vibrational (red) Kondo excitations separate into two groups. Exponential fits (solid lines) evidence the different contribution of each process to the decoherence rate.

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Spin Relaxation

Key research themes

1. How can cavity quantum electrodynamics be employed to control and enhance spin relaxation rates in solid-state systems?

2. What are the microscopic mechanisms and theoretical frameworks governing spin relaxation and spin polarization in relativistic and strongly interacting spin-1/2 systems?

3. How do structural properties, anisotropies, and nanoscale confinement influence spin relaxation phenomena in semiconductor nanostructures and porous materials?

4. What advances in measurement techniques enable probing ultrafast spin-lattice and spin-spin relaxation processes inaccessible by conventional methods?

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