6,487 research outputs found
A Discrete Version of the Inverse Scattering Problem and the J-matrix Method
The problem of the Hamiltonian matrix in the oscillator and Laguerre basis
construction from the S-matrix is treated in the context of the algebraic
analogue of the Marchenko method.Comment: 11 pages. The Laguerre basis case is adde
Quasiclassical approach to the spin-Hall effect in the two-dimensional electron gas
We study the spin-charge coupled transport in a two-dimensional electron
system using the method of quasiclassical (-integrated) Green's functions.
In particular we derive the Eilenberger equation in the presence of a generic
spin-orbit field. The method allows us to study spin and charge transport from
ballistic to diffusive regimes and continuity equations for spin and charge are
automatically incorporated. In the clean limit we establish the connection
between the spin-Hall conductivity and the Berry phase in momentum space. For
finite systems we solve the Eilenberger equation numerically for the special
case of the Rashba spin-orbit coupling and a two-terminal geometry. In
particular, we calculate explicitly the spin-Hall induced spin polarization in
the corners, predicted by Mishchenko et al. [13]. Furthermore we find universal
spin currents in the short-time dynamics after switching on the voltage across
the sample, and calculate the corresponding spin-Hall polarization at the
edges. Where available, we find perfect agreement with analytical results.Comment: 9 pages, 6 figure
Chirality sensitive effect on surface states in chiral p-wave superconductors
We study the local density of states at the surface of a chiral p-wave
superconductor in the presence of a weak magnetic field. As a result, the
formation of low-energy Andreev bound states is either suppressed or enhanced
by an applied magnetic field, depending on its orientation with respect to the
chirality of the p-wave superconductor. Similarly, an Abrikosov vortex, which
is situated not too far from the surface, leads to a zero-energy peak of the
density of states, if its chirality is the same as that of the superconductor,
and to a gap structure for the opposite case. We explain the underlying
principle of this effect and propose a chirality sensitive test on
unconventional superconductors.Comment: 4 pages, 2 figure
Quasiparticle states of the Hubbard model near the Fermi level
The spectra of the t-U and t-t'-U Hubbard models are investigated in the
one-loop approximation for different values of the electron filling. It is
shown that the four-band structure which is inherent in the case of
half-filling and low temperatures persists also for some excess or deficiency
of electrons. Besides, with some departure from half-filling an additional
narrow band of quasiparticle states arises near the Fermi level. The dispersion
of the band, its bandwidth and the variation with filling are close to those of
the spin-polaron band of the t-J model. For moderate doping spectral
intensities in the new band and in one of the inner bands of the four-band
structure decrease as the Fermi level is approached which leads to the
appearance of a pseudogap in the spectrum.Comment: 8 pages, 7 figure
ac Josephson effect in asymmetric superconducting quantum point contacts
We investigate ac Josephson effects between two superconductors connected by
a single-mode quantum point contact, where the gap amplitudes in the two
superconductors are unequal. In these systems, it was found in previous studies
on the dc effects that, besides the Andreev bound-states, the continuum states
can also contribute to the current. Using the quasiclassical formulation, we
calculate the current-voltage characteristics for general transmission of
the point contact. To emphasize bound versus continuum states, we examine in
detail the low bias, ballistic (D=1) limit. It is shown that in this limit the
current-voltage characteristics can be determined from the current-phase
relation, if we pay particular attention to the different behaviors of these
states under the bias voltage. For unequal gap configurations, the continuum
states give rise to non-zero sine components. We also demonstrate that in this
limit the temperature dependence of the dc component follows
, where is the smaller gap, with the
contribution coming entirely from the bound state.Comment: To appear in PR
Energy dependence of current noise in superconducting/normal metal junctions
Interference of electronic waves undergoing Andreev reflection in diffusive
conductors determines the energy profile of the conductance on the scale of the
Thouless energy. A similar dependence exists in the current noise, but its
behavior is known only in few limiting cases. We consider a metallic diffusive
wire connected to a superconducting reservoir through an interface
characterized by an arbitrary distribution of channel transparencies. Within
the quasiclassical theory for current fluctuations we provide a general
expression for the energy dependence of the current noise.Comment: 5 pages, 1 Figur
One-dimensional conduction in Charge-Density Wave nanowires
We report a systematic study of the transport properties of coupled
one-dimensional metallic chains as a function of the number of parallel chains.
When the number of parallel chains is less than 2000, the transport properties
show power-law behavior on temperature and voltage, characteristic for
one-dimensional systems.Comment: 4 pages, 5 figures, submitted to Phys. Rev. Let
NN potentials from inverse scattering in the J-matrix approach
An approximate inverse scattering method [7,8] has been used to construct
separable potentials with the Laguerre form factors. As an application, we
invert the phase shifts of proton-proton in the and
channels and neutron-proton in the channel elastic scattering. In
the latter case the deuteron wave function of a realistic potential was
used as input.Comment: LaTex2e, 17 pages, 3 Postscript figures; corrected typo
Theory of thermal and charge transport in diffusive normal metal / superconductor junctions
Thermal and charge transport in the diffusive normal metal(DN) / insulator /
-, - and p-wave superconductor junctions are studied for various
situations, where we have used the Usadel equation with Nazarov's generalized
boundary condition. Thermal and electrical conductance of the junction and the
Lorentz ratio are calculated by varying the magnitudes of the resistance, the
Thouless energy and the magnetic scattering rate in DN, the transparency of the
insulating barrier, and the angle between the normal to the interface and the
crystal axis of d-wave superconductors or the angle between the normal to the
interface and the lobe direction of the p-wave pair potential. New general
expression is derived for the calculation of the thermal conductance. It is
demonstrated that the proximity effect doesn't influence the thermal
conductance while the mid gap Andreev resonant states suppress it. We have also
discussed a possibility of distinguishing pairing symmetries based on the
dependencies of the electrical and thermal conductance on temperatures.Comment: 21 pages, 20 figures, stylistic changes in v
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