scholarly journals Distinct properties of vortex bound states driven by temperature

2021 ◽  
Author(s):  
Xinwei Fan ◽  
Xiaoyu Chen ◽  
Huan Yang ◽  
Hai-Hu Wen
Keyword(s):  
Bound States ◽  
Local Density ◽  
Pair Potential ◽  
Quantum Limit ◽  
Local Density Of States ◽  
Comprehensive Understanding ◽  
Gennes Equation ◽  
Temperature Regimes ◽  
Analytical Result ◽  
Distinct Features

Abstract We investigate the behavior of vortex bound states in the quantum limit by self-consistently solving the Bogoliubov-de Gennes equation.\revision{We find that the energies of the vortex bound states deviates from the analytical result $E_\mu=\mu\Delta^2/E_F$ with the half-integer angular momentum $\mu$ at very low temperature. Specifically, the energy ratio for the first three orders is more close to $1:2:3$ instead of $1:3:5$ in the extreme quantum limit $T/T_c\ll\Delta/E_F$.} The local density of states reveals a Friedel-like behavior associated with that of the pair potential, which will be smoothed out by thermal effect above the quantum limit. Our studies show that the vortex bound states can exhibit very distinct features in different temperature regimes, which provides a comprehensive understanding and should stimulate more experimental efforts for verifications.

Aspects of a Single Vortex in d-Wave Superconductors

1998 ◽  
Vol 12 (10) ◽  
pp. 989-1005 ◽  
Author(s):  
Y. Morita ◽  
M. Kohmoto ◽  
K. Maki
Keyword(s):  
Density Of States ◽  
Bound States ◽  
Local Density ◽  
Quantum Limit ◽  
Vortex Center ◽  
Local Density Of States ◽  
S Wave ◽  
Single Vortex ◽  
Quasiparticle Spectrum ◽  
D Wave

Physical properties of a single vortex in d-wave superconductors are studied theoretically. After a brief review on a single vortex in "conventional" s-wave superconductors and the d-wave superconductivity underlying the hole-doped high-T c cuprates, we go on to study the quasiparticle spectrum around a single vortex in the high-T c superconductors. One of the characteristics of the high-T c superconductors is that they are close to the "quantum limit" (pFξ ~ O(1)). A new picture emerges of the quasiparticle spectrum. Instead of thousands of bound states in a "conventional" s-wave superconductor, we find only a few peaks in the local density of states at the vortex center. Further there are low-lying excitations stretched in four diagonal directions and they have no counterpart in s-wave superconductors.

scholarly journals Near-Field Excitation of Bound States in the Continuum in All-Dielectric Metasurfaces through a Coupled Electric/Magnetic Dipole Model

Nanomaterials ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 998
Author(s):  
Diego R. Abujetas ◽  
José A. Sánchez-Gil
Keyword(s):  
Magnetic Dipole ◽  
Density Of States ◽  
Bound States ◽  
Local Density ◽  
Near Field ◽  
Field Pattern ◽  
Local Density Of States ◽  
Optical Modes ◽  
Source Excitation ◽  
The Continuum

Resonant optical modes arising in all-dielectric metasurfaces have attracted much attention in recent years, especially when so-called bound states in the continuum (BICs) with diverging lifetimes are supported. With the aim of studying theoretically the emergence of BICs, we extend a coupled electric and magnetic dipole analytical formulation to deal with the proper metasurface Green function for the infinite lattice. Thereby, we show how to excite metasurface BICs, being able to address their near-field pattern through point-source excitation and their local density of states. We apply this formulation to fully characterize symmetry-protected BICs arising in all-dielectric metasurfaces made of Si nanospheres, revealing their near-field pattern and local density of states, and, thus, the mechanisms precluding their radiation into the continuum. This formulation provides, in turn, an insightful and fast tool to characterize BICs (and any other leaky/guided mode) near fields in all-dielectric (and also plasmonic) metasurfaces, which might be especially useful for the design of planar nanophotonic devices based on such resonant modes.

Local Density of States of a Three-Dimensional Conductor in the Extreme Quantum Limit

2001 ◽  
Vol 86 (8) ◽  
pp. 1582-1585 ◽  
Author(s):  
D. Haude ◽  
M. Morgenstern ◽  
I. Meinel ◽  
R. Wiesendanger
Keyword(s):  
Density Of States ◽  
Local Density ◽  
Three Dimensional ◽  
Quantum Limit ◽  
Local Density Of States

Vibrational Properties of Vacancy in Na and K Using MEAM Potential

2014 ◽  
Vol 15 (2) ◽  
pp. 556-568 ◽  
Author(s):  
Vandana Gairola ◽  
P. D. Semalty
Keyword(s):  
Density Of States ◽  
Alkali Metals ◽  
Phonon Dispersion ◽  
Local Density ◽  
Pair Potential ◽  
Vacancy Formation ◽  
Mean Square ◽  
Local Density Of States ◽  
Embedded Atom ◽  
Cauchy Pressure

AbstractThe modified embedded atom method (MEAM) with the universal form of embedding function and a modified energy term along with the pair potential has been employed to determine the potentials for alkali metals: Na, K, by fitting to the Cauchy pressure (C12 − C44)/2, shear constants Gν = (C11 − C12 + 3C44)/5 and C44, the cohesive energy and the vacancy formation energy. The obtained potentials are used to calculate the phonon dispersions of these metals. Using these calculated phonons we evaluate the local density of states of neighbours of vacancy using Green’s function method. The local density of states of neighbours of vacancy has been used to calculate mean square displacements of these atoms and formation entropy of vacancy. The calculated mean square displacements of both 1st and 2nd neighbours of vacancy are found to be lower than that of host atom. The calculated phonon dispersions agree well with the experimental phonon dispersion curves and the calculated results of vacancy formation entropy compare well with the other available results.

scholarly journals Study on Green’s function on topological insulator surface

2018 ◽  
Vol 376 (2125) ◽  
pp. 20150246 ◽  
Author(s):  
Bo Lu ◽  
Yukio Tanaka
Keyword(s):  
Green’S Function ◽  
Density Of States ◽  
Green's Function ◽  
Topological Insulator ◽  
Bound States ◽  
Local Density ◽  
Josephson Current ◽  
Majorana Fermion ◽  
Local Density Of States ◽  
Andreev Bound States

In the theory of superconducting junctions, Green’s function has an important role for obtaining Andreev bound states, local density of states and Josephson current in a systematic way. In this article, we show how to construct Green’s function on the surface of a topological insulator following McMillan’s formalism where the energy spectrum of electrons obeys a linear dispersion. For a model of a superconductor (S)/ferromagnet (F)/normal metal (N) junction, we show that the generation of a Majorana fermion gives rise to the enhanced local density of states and pair amplitude of odd-frequency pairing. We also derive an extended Furusaki–Tsukada’s formula of DC Josephson current in S/F/S junctions. The obtained Josephson current depends on the direction and magnitude of the magnetization. This article is part of the theme issue ‘Andreev bound states’.

scholarly journals PLANAR MASSLESS FERMIONS IN COULOMB AND AHARONOV–BOHM POTENTIALS

2012 ◽  
Vol 27 (29) ◽  
pp. 1250169 ◽  
Author(s):  
V. R. KHALILOV ◽  
K. E. LEE
Keyword(s):  
Quantum Electrodynamics ◽  
Bound States ◽  
Local Density ◽  
Local Density Of States ◽  
Charged Fermion ◽  
Adjoint Extension ◽  
Effective Charges ◽  
Aharonov Bohm ◽  
Dirac Hamiltonian ◽  
Massless Fermions

Solutions to the Dirac equation are constructed for a massless charged fermion in Coulomb and Aharonov–Bohm (AB) potentials in 2+1 dimensions. The Dirac Hamiltonian on this background is singular and needs a one-parameter self-adjoint extension, which can be given in terms of self-adjoint boundary conditions. We show that the virtual (quasistationary) bound states emerge in the presence of an attractive Coulomb potential when the so-called effective charges become overcritical and discuss a restructuring of the vacuum of the quantum electrodynamics when the virtual bound states emerge. We derive equations, which determine the energies and lifetimes of virtual bound states, find solutions of obtained equations for some values of parameters as well as analyze the local density of states (LDOS) as a function of energy in the presence of Coulomb and AB potentials.

IMPURITY EFFECT ON THE TRANSITION TEMPERATURE OF THE SUPERCONDUCTING FULLERIDES

2011 ◽  
Vol 25 (12) ◽  
pp. 1577-1584
Author(s):  
H. HUANG ◽  
Z.-Z. GAN
Keyword(s):  
Transition Temperature ◽  
Alkali Metal ◽  
Bound States ◽  
Local Density ◽  
Average Distance ◽  
Impurity Effect ◽  
Local Density Of States ◽  
Impurity Potential ◽  
Impurity Model ◽  
Metal Doped

We study the alkali-metal-doped fulleride systems based on an impurity model. The bound states are induced by the impurity potential, and the local density of states of the neighboring molecules at the Fermi level is remarkably reduced. We point out that the superconductivity of the whole system will be destroyed when the average distance between the impurities reaches the order of the coherence length. It gives a reasonable explanation to the strange behavior of the transition temperature of the superconducting fullerides.

Effects of Grain-Boundaries in Superconducting Materials

1997 ◽  
Vol 491 ◽  
Author(s):  
J. J. Hogan-O'Neill ◽  
A. M. Martin ◽  
James F. Annett
Keyword(s):  
Grain Boundaries ◽  
Order Parameter ◽  
Lattice Structure ◽  
Local Density ◽  
Geometrical Model ◽  
Critical Currents ◽  
Local Density Of States ◽  
Recursion Method ◽  
Gennes Equation ◽  
Self Consistent

ABSTRACTWe examine the effects of grain-boundaries on the order-parameter and critical-currents in superconductors. We use a geometrical model of the lattice structure of grain-boundaries. We solve the Bogoliubov-de Gennes equation using the Recursion Method to obtain the self-consistent BCS gap function Δ and the local density of states N(E) near the boundary. Imposing a phase difference across the boundary we calculate the supercurrent and hence obtain the critical-current, Ic, of the junction.

scholarly journals Supersymmetric Cluster Expansions and Applications to Random Schrödinger Operators

2021 ◽  
Vol 24 (1) ◽  
Author(s):  
Luca Fresta
Keyword(s):  
Density Of States ◽  
Local Density ◽  
Schrödinger Operators ◽  
Random Schrödinger Operators ◽  
Schrodinger Operators ◽  
Local Density Of States ◽  
Weak Disorder ◽  
Cluster Expansions ◽  
Strong Disorder ◽  
Lifshitz Tail

AbstractWe study discrete random Schrödinger operators via the supersymmetric formalism. We develop a cluster expansion that converges at both strong and weak disorder. We prove the exponential decay of the disorder-averaged Green’s function and the smoothness of the local density of states either at weak disorder and at energies in proximity of the unperturbed spectrum or at strong disorder and at any energy. As an application, we establish Lifshitz-tail-type estimates for the local density of states and thus localization at weak disorder.

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