533 research outputs found
Combination quantum oscillations in canonical single-band Fermi liquids
Chemical potential oscillations mix individual-band frequencies of the de
Haas-van Alphen (dHvA) and Shubnikov-de Haas (SdH) magneto-oscillations in
canonical low-dimensional multi-band Fermi liquids. We predict a similar mixing
in canonical single-band Fermi liquids, which Fermi-surfaces have two or more
extremal cross-sections. Combination harmonics are analysed using a single-band
almost two-dimensional energy spectrum. We outline some experimental conditions
allowing for resolution of combination harmonics
Numerical simulation evidence of spectrum rearrangement in impure graphene
By means of numerical simulation we confirm that in graphene with point
defects a quasigap opens in the vicinity of the resonance state with increasing
impurity concentration. We prove that states inside this quasigap cannot longer
be described by a wavevector and are strongly localized. We visualize states
corresponding to the density of states maxima within the quasigap and show that
they are yielded by impurity pair clusters
Matter-wave analog of an optical random laser
The accumulation of atoms in the lowest energy level of a trap and the
subsequent out-coupling of these atoms is a realization of a matter-wave analog
of a conventional optical laser. Optical random lasers require materials that
provide optical gain but, contrary to conventional lasers, the modes are
determined by multiple scattering and not a cavity. We show that a
Bose-Einstein condensate can be loaded in a spatially correlated disorder
potential prepared in such a way that the Anderson localization phenomenon
operates as a band-pass filter. A multiple scattering process selects atoms
with certain momenta and determines laser modes which represents a matter-wave
analog of an optical random laser.Comment: 4 pages, 3 figures version accepted for publication in Phys. Rev. A;
minor changes, the present title substituted for "Atom Random Laser
The effect of electronic entropy on temperature peculiarities of the frequency characteristics of two interacting anharmonic vibrational modes in Zr
A 2D temperature-dependent effective potential is calculated for the
interacting longitudinal and transverse phonons of zirconium in the
frozen-phonon model. The effective potentials obtained for different
temperatures are used for the numerical solution of a set of stochastic
differential equations with a thermostat of the white-noise type. Analysis of
the spectral density of transverse vibrations allows one to determine the
temperature at which -Zr becomes unstable with respect to the
longitudinal vibrations. The obtained temperature value practically
coincides with the experimental temperature of the
structural transition in zirconium. The role of electronic entropy in the
Zr stability is discussed.Comment: 9 pages, 10 figures (submitted in Phys.Rev.
The spatial statistical properties of wave functions in a disordered finite one-dimensional sample
For a given wave function one can define a quantity having a meaning
of its inverse spatial size. The Laplace transform of the distribution function
is calculated analytically for a 1D disordered sample with a finite
length .Comment: LaTEX, 7 pages, Preprint IFUM-456/FT, Milano, Jan.199
1D-Disordered Conductor with Loops Immersed in a Magnetic Field
We investigate the conductance of a 1-D disordered conducting loop with two
contacts, immersed in a magnetic flux. We show the appearance in this model of
the Al'tshuler-Aronov-Spivak behaviour. We also investigate the case of a chain
of loops distributed with finite density: in this case we show that the
interference effects due to the presence of the loops can lead to the
delocalization of the wave function.Comment: 8 pages; LaTeX; IFUM 463/FT; to appear in Phys. Lett.
Nonequilibrium transport and optical properties of model metal--Mott-insulator--metal heterostructures
Electronic properties of heterostructures in which a finite number of
Mott-insulator layers are sandwiched by semi-infinite metallic leads are
investigated by using the dynamical-mean-field method combined with the Keldysh
Green's function technique to account for the finite bias voltage between the
leads. Current across the junction is computed as a function of bias voltage.
Electron spectral functions in the interacting region are shown to evolve by an
applied bias voltage. This effect is measurable by photoemission spectroscopy
and scanning tunneling microscopy. Further predictions are made for the optical
conductivity under a bias voltage as a possible tool to detect a deformed
density of states. A general discussion of correlated-electron based
heterostructures and future prospect is given.Comment: 11 pages, 11 figures, published versio
Paramagnetic limit of superconductivity in a crystal without inversion center
The theory of paramagnetic limit of superconductivity in metals without
inversion center is developed. There is in general the paramagnetic suppression
of superconducting state. The effect is strongly dependent on field orientation
in respect to crystal axes. The reason for this is that the degeneracy of
electronic states with opposite momenta forming of Cooper pairs is lifted by
magnetic field but for some field directions this lifting can be small or even
absent.Comment: 9 pages, no figure
Magnetic quantum oscillations in doped antiferromagnetic insulators
Energy spectrum of electrons (holes) doped into a two-dimensional
antiferromagnetic insulator is quantized in an external magnetic field of
arbitrary direction. A peculiar dependence of de Haas-van Alphen (dHvA) or
Shubnikov-de Haas (SdH) magneto-oscillation amplitudes on the azimuthal
in-plane angle from the magnetization direction and on the polar angle from the
out-of-plane direction is found, which can be used as a sensitive probe of the
antiferromagnetic order in doped Mott-Hubbard, spin-density wave (SDW), and
conventional band-structure insulators.Comment: 4 pages 4 figure
The spectral shift function and Levinson's theorem for quantum star graphs
We consider the Schr\"odinger operator on a star shaped graph with edges
joined at a single vertex. We derive an expression for the trace of the
difference of the perturbed and unperturbed resolvent in terms of a Wronskian.
This leads to representations for the perturbation determinant and the spectral
shift function, and to an analog of Levinson's formula
- …