Near-field dipolar plasmon interactions of multiple infrared antenna structures in the strong cou... more Near-field dipolar plasmon interactions of multiple infrared antenna structures in the strong coupling limit are studied using scattering-type scanning near-field optical microscope (s-SNOM) and theoretical finite-difference time-domain (FDTD) calculations. We monitor in real-space the evolution of plasmon dipolar mode of a stationary antenna structure as multiple resonantly matched dipolar plasmon particles are closely approaching it. Interparticle separation, length and polarization dependent studies show that the cross geometry structure favors strong interparticle charge–charge, dipole–dipole and charge–dipole Coulomb interactions in the nanometer scale gap region, which results in strong field enhancement in cross-bowties and further allows these structures to be used as polarization filters. The nanoscale local field amplitude and phase maps show that due to strong interparticle Coulomb coupling, cross-bowtie structures redistribute and highly enhance the out-of-plane (perpendicular to the plane of the sample) plasmon near-field component at the gap region relative to ordinary bowties.
We propose a finite dimensional representation for the potential operator such that it retains so... more We propose a finite dimensional representation for the potential operator such that it retains some information about the whole Hilbert-space representation. The potential should be represented in a larger basis, then the matrix should be inverted, then truncated to the desired size, and finally inverted again. This procedure results in a superb low-rank representation of the potential operator.
In the strong coupling regime that is relevant to heavy-fermion systems, we can approach the proh... more In the strong coupling regime that is relevant to heavy-fermion systems, we can approach the prohibition of dσ fermion double occupancy by an auxiliary boson method (1). Representing d † iσ = f † iσ bi , the f † iσ (bi ) are fermonic (bosonic) operators satisfying the constraint b † i bi + σ f † iσ fiσ = 1. At the saddlepoint level, we replace b † i , bi → r and introduce a Lagrange multiplier to enforce the local constraint.
Insulating states can be topologically nontrivial, a well-established notion that is exemplified ... more Insulating states can be topologically nontrivial, a well-established notion that is exemplified by the quantum Hall effect and topological insulators. By contrast, topological metals have not been experimentally evidenced until recently. In systems with strong correlations, they have yet to be identified. Heavy-fermion semimetals are a prototype of strongly correlated systems and, given their strong spin-orbit coupling, present a natural setting to make progress. Here, we advance a Weyl–Kondo semimetal phase in a periodic Anderson model on a noncentrosymmetric lattice. The quasiparticles near the Weyl nodes develop out of the Kondo effect, as do the surface states that feature Fermi arcs. We determine the key signatures of this phase, which are realized in the heavy-fermion semimetal Ce 3 Bi 4 Pd 3. Our findings provide the much-needed theoretical foundation for the experimental search of topological metals with strong correlations and open up an avenue for systematic studies of such quantum phases that naturally entangle multiple degrees of freedom.
Bi 2 Se 3 thin films are imaged in the near-field using spectroscopic scattering type near-field ... more Bi 2 Se 3 thin films are imaged in the near-field using spectroscopic scattering type near-field optical microscopy (s-SNOM) at mid infrared laser wavelength region (9-11μm). Single phases Bi 2 Se 3 thin film structures were prepared by mechanical exfoliation on silicon wafers. We report size and wavelength dependent near-field interaction contrasts in both optical amplitude and phase. We show that near-field optical imaging allows material specific identification and characterization of Bi 2 Se 3 exfoliated samples including the confirmation of residual tape presence or removal in stacked films. We describe an alternative "shear exfoliation" sample preparation method which reliably deposits Bi 2 Se 3 without the possibility of adhesive contaminants.
Approximations of potentials through the truncation of their inverses
Physical Review C, 2013
ABSTRACT The inverse of an $\infty \times \infty$ symmetric band matrix can be constructed in ter... more ABSTRACT The inverse of an $\infty \times \infty$ symmetric band matrix can be constructed in terms of a matrix continued fraction. For Hamiltonians with Coulomb plus polynomial potentials, this results in an exact and analytic Green's operator which, even in finite-dimensional representation, exhibits the exact spectrum. In this work we propose a finite dimensional representation for the potential operator such that it retains some information about the whole Hilbert-space representation. The potential should be represented in a larger basis, then the matrix should be inverted, then truncated to the desired size, and finally inverted again. This procedure results in a superb low-rank representation of the potential operator. The method is illustrated with a typical nucleon-nucleon potential.
Near-field dipolar plasmon interactions of multiple infrared antenna structures in the strong cou... more Near-field dipolar plasmon interactions of multiple infrared antenna structures in the strong coupling limit are studied using scattering-type scanning near-field optical microscope (s-SNOM) and theoretical finite-difference time-domain (FDTD) calculations. We monitor in real-space the evolution of plasmon dipolar mode of a stationary antenna structure as multiple resonantly matched dipolar plasmon particles are closely approaching it. Interparticle separation, length and polarization dependent studies show that the cross geometry structure favors strong interparticle charge-charge, dipole-dipole and charge-dipole Coulomb interactions in the nanometer scale gap region, which results in strong field enhancement in cross-bowties and further allows these structures to be used as polarization filters.
Spectrally resolved fluorescence lifetime imaging microscope using tunable bandpass filters Rev. ... more Spectrally resolved fluorescence lifetime imaging microscope using tunable bandpass filters Rev. Sci. Instrum. 83, 093705 (2012) Improving the signal-to-noise ratio of high-speed contact mode atomic force microscopy Rev. Sci. Instrum. 83, 083710 (2012) Image acceleration in parallel magnetic resonance imaging by means of metamaterial magnetoinductive lenses AIP Advances 2, 022136 Virtual ghost imaging through turbulence and obscurants using Bessel beam illumination Appl. Phys. Lett. 100, 061126 Versatile multispectral microscope based on light emitting diodes Rev. Sci. Instrum. 82, 123106 (2011) Additional information on Appl. Phys. Lett.
Bulletin of the American Physical Society, Mar 6, 2015
Submitted for the MAR15 Meeting of The American Physical Society Quantum phase transition and ano... more Submitted for the MAR15 Meeting of The American Physical Society Quantum phase transition and anomalous Hall effect in a pyrochlore Kondo lattice SARAH GREFE, WENXIN DING, QIMIAO SI, Rice University -Motivated by recent experimental evidence for a possible chiral spin liquid phase in the metallic pyrochlore heavy fermion iridates (P r 2 Ir 2 O 7 ) [Phys.Rev.Lett, 96, 087204 (2006), Phys.Rev.Lett 98, 057203 (2007), Nature 463, 210 (2010)] as well as quantum critical behavior in this system [Nat. Mater. 13, 356
Studies on the heavy-fermion pyrochlore iridate (Pr2Ir2O7) point to the role of time-reversal-sym... more Studies on the heavy-fermion pyrochlore iridate (Pr2Ir2O7) point to the role of time-reversal-symmetry breaking in geometrically frustrated Kondo lattices. Here we address the effect of Kondo coupling and chiral spin liquids in a J1 − J2 model on a square lattice and in a model on a Kagomé lattice. We calculate the anomalous Hall response for the chiral states of both the Kondo destroyed and Kondo screened phases. Across the quantum critical point, the anomalous Hall coefficient jumps when there is a sudden reconstruction of Fermi surfaces. We discuss the implications of our results for the heavy-fermion pyrochlore iridate and propose an interface structure based on Kondo insulators to further explore such effects.
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