76 research outputs found
Fermi Liquid Properties of a Two Dimensional Electron System With the Fermi Level Near a van Hove Singularity
We use a diagrammatic approach to study low energy physics of a two
dimensional electron system where the Fermi level is near van-Hove singularies
in the energy spectrum. We find that in most regions of the
phase diagram the system behaves as a normal Fermi liquid rather than a
marginal Fermi liquid. Particularly, the imaginary part of the self energy is
much smaller than the excitation energy, which implies well defined
quasiparticle excitations, and single particle properties are only weakly
affected by the presence of the van-Hove singularities. The relevance to high
temperature superconductivity is also discussed.Comment: 10 pages, 4 postscript figure
RKKY interaction in the nearly-nested Fermi liquid
We present the results of analytical evaluation of the indirect RKKY
interaction in a layered metal with nearly nested (almost squared) Fermi
surface. The final expressions are obtained in closed form as a combination of
Bessel functions. We discuss the notion of the
``2k_F'' oscillations and show that they occur as the far asymptote of our
expressions. We show the existence of the intermediate asymptote of the
interaction which is of the sign-reversal antiferromagnetic type and is the
only term surviving in the limit of exact nesting. A good accordance of our
analytical formulas with numerical findings is demonstrated until the
interatomic distances. The obtained expressions for the Green's functions
extend the previous analytical results into the region of intermediate
distances as well.Comment: 9 pages, REVTEX, 3 .eps figures, to appear in PRB 1 Oct 199
Reply to ``Comment on `Magnetic field effects on neutron diffraction in the antiferromagnetic phase of '''
Fak, van Dijk and Wills (FDW) question our interpretation of elastic
neutron-scattering experiments in the antiferromagnetic phase of UPt_3. They
state that our analysis is incorrect because we average over magnetic
structures that are disallowed by symmetry. We disagree with FDW and reply to
their criticism. FDW also point out that we have mistaken the magnetic field
direction in the experiment reported by N. H. van Dijk et al. [Phys. Rev. B 58,
3186 (1998)]. We correct this error and note that our previous conclusion is
also valid for the correct field orientation.Comment: 3 page
Bi-quadratic magnetoelectric coupling in underdoped La_2CuO_{4+x}
The recent discovery of relaxor ferroelectricity and magnetoelectric effect
in lightly doped cuprate material La_2CuO_{4+x} has provided a number of
questions concerning its theoretical description. It has been argued using a
Ginzburg-Landau free energy approach that the magnetoelectric effect can be
explained by the presence of bi-quadratic interaction terms in the free energy.
Here, by using the same free energy functional, we study the variety of
behavior which can emerge in the electric polarization under an external
magnetic field. Subsequently, we discuss the role of Dzyaloshinskii-Moriya
interaction in generating this magnetoelectric response. This work is
particularly relevant for such relaxor systems where the material-dependent
parameters would be affected by changes in e.g. chemical doping or cooling
rate.Comment: 8 pages, 2 figures. arXiv admin note: text overlap with
arXiv:1112.152
Breakup of a Stoner model for the 2D ferromagnetic quantum critical point
Re-interpretation of the results by [A. V. Chubukov et. al., Phys. Rev. Lett.
90, 077002 (2003)] leads to the conclusion that ferromagnetic quantum critical
point (FQCP) cannot be described by a Stoner model because of a strong
interplay between the paramagnetic fluctuations and the Cooper channel, at
least in two dimensions.Comment: 5 pages, 2 EPS figures, RevTeX
Spin relaxation and antisymmetric exchange in n-doped III-V semiconductor
Recently K. Kavokin [Phys. Rev. B 64, 075305 (2001)] suggested that the
Dzyaloshinskii-Moriya interaction between localized electrons governs slow spin
relaxation in -doped GaAs in the regime close to the metal-insulator
transition. We derive the correct spin Hamiltonian and apply it to the
determination of spin dephasing time using the method of moments expansion. We
argue that the proposed mechanism is insufficient to explain the observed
values of the spin relaxation time.Comment: 5 pages, 1 figure
Numerical study of the one-dimensional quantum compass model
The ground state magnetic phase diagram of the one-dimensional quantum
compass model (QCM) is studied using the numerical Lanczos method. A detailed
numerical analysis of the low energy excitation spectrum is presented. The
energy gap and the spin-spin correlation functions are calculated for finite
chains. Two kind of the magnetic long-range orders, the Neel and a type of the
stripe-antiferromagnet, in the ground state phase diagram are identified. Based
on the numerical analysis, the first and second order quantum phase transitions
in the ground state phase diagram are identified.Comment: 6 pages, 8 figures. arXiv admin note: text overlap with
arXiv:1105.211
Transport of interacting electrons through a double barrier in quantum wires
We generalize the fermionic renormalization group method to describe
analytically transport through a double barrier structure in a one-dimensional
system. Focusing on the case of weakly interacting electrons, we investigate
thoroughly the dependence of the conductance on the strength and the shape of
the double barrier for arbitrary temperature T. Our approach allows us to
systematically analyze the contributions to renormalized scattering amplitudes
from different characteristic scales absent in the case of a single impurity,
without restricting the consideration to the model of a single resonant level.
Both a sequential resonant tunneling for high T and a resonant transmission for
T smaller than the resonance width are studied within the unified treatment of
transport through strong barriers. For weak barriers, we show that two
different regimes are possible. Moderately weak impurities may get strong due
to a renormalization by interacting electrons, so that transport is described
in terms of theory for initially strong barriers. The renormalization of very
weak impurities does not yield any peak in the transmission probability;
however, remarkably, the interaction gives rise to a sharp peak in the
conductance, provided asymmetry is not too high.Comment: 18 pages, 8 figures; figures added, references updated, extended
discussio
Casimir Dispersion Forces and Orientational Pairwise Additivity
A path integral formulation is used to study the fluctuation-induced
interactions between manifolds of arbitrary shape at large separations. It is
shown that the form of the interactions crucially depends on the choice of the
boundary condition. In particular, whether or not the Casimir interaction is
pairwise additive is shown to depend on whether the ``metallic'' boundary
condition corresponds to a ``grounded'' or an ``isolated'' manifold.Comment: 6 pages, RevTe
Functional Integral Bosonization for Impurity in Luttinger Liquid
We use a functional integral formalism developed earlier for the pure
Luttinger liquid (LL) to find an exact representation for the electron Green
function of the LL in the presence of a single backscattering impurity. This
allows us to reproduce results (well known from the bosonization techniques)
for the suppression of the electron local density of states (LDoS) at the
position of the impurity and for the Friedel oscillations at finite
temperature. In addition, we have extracted from the exact representation an
analytic dependence of LDoS on the distance from the impurity and shown how it
crosses over to that for the pure LL.Comment: 7 pages, 1 LaTeX produced figur
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