Ambipolar Nernst effect in NbSe2_2

The first study of Nernst effect in NbSe$_2$ reveals a large quasi-particle contribution with a magnitude comparable and a sign opposite to the vortex signal. Comparing the effect of the Charge Density Wave(CDW) transition on Hall and Nernst coefficients, we argue that this large Nernst signal originates from the thermally-induced counterflow of electrons and holes and indicates a drastic change in the electron scattering rate in the CDW state. The results provide new input for the debate on the origin of the anomalous Nernst signal in high-T$_c$ cuprates.Comment: 5 pages including 4 figure

Universal Scaling Behavior of Anomalous Hall Effect and Anomalous Nernst Effect in Itinerant Ferromagnets

Anomalous Hall effect (AHE) and anomalous Nernst effect (ANE) in a variety of ferromagnetic metals including pure metals, oxides, and chalcogenides, are studied to obtain unified understandings of their origins. We show a universal scaling behavior of anomalous Hall conductivity $\sigma_{xy}$ as a function of longitudinal conductivity $\sigma_{xx}$ over five orders of magnitude, which is well explained by a recent theory of the AHE taking into account both the intrinsic and extrinsic contributions. ANE is closely related with AHE and provides us with further information about the low-temperature electronic state of itinerant ferromagnets. Temperature dependence of transverse Peltier coefficient $\alpha_{xy}$ shows an almost similar behavior among various ferromagnets, and this behavior is in good agreement quantitatively with that expected from the Mott rule.Comment: 4pages, 4figures, 1tabl

Electrical Resistivity of a Thin Metallic Film

The electrical resistivity of a pure sample of a thin metallic film is found to depend on the boundary conditions. This conclusion is supported by a free-electron model calculation and confirmed by an ab initio relativistic Korringa-Kohn-Rostoker computation. The low-temperature resistivity is found to be zero for a free-standing film (reflecting boundary conditions) but nonzero when the film is sandwiched between two semi-infinite samples of the same material (outgoing boundary conditions). In the latter case, this resistivity scales inversely with the number of monolayers and is due to the background diffusive scattering by a finite lattice.Comment: 20 pages. To be published in Physical Review B, December 15, 199

Integral equation for inhomogeneous condensed bosons generalizing the Gross-Pitaevskii differential equation

We give here the derivation of a Gross-Pitaevskii--type equation for inhomogeneous condensed bosons. Instead of the original Gross-Pitaevskii differential equation, we obtain an integral equation that implies less restrictive assumptions than are made in the very recent study of Pieri and Strinati [Phys. Rev. Lett. 91 (2003) 030401]. In particular, the Thomas-Fermi approximation and the restriction to small spatial variations of the order parameter invoked in their study are avoided.Comment: Phys. Rev. A (accepted

Path-decomposition expansion and edge effects in a confined magnetized free-electron gas

Path-integral methods can be used to derive a `path-decomposition expansion' for the temperature Green function of a magnetized free-electron gas confined by a hard wall. With the help of this expansion the asymptotic behaviour of the profiles for the excess particle density and the electric current density far from the edge is determined for arbitrary values of the magnetic field strength. The asymptotics are found to depend sensitively on the degree of degeneracy. For a non-degenerate electron gas the asymptotic profiles are essentially Gaussian (albeit modulated by a Bessel function), on a length scale that is a function of the magnetic field strength and the temperature. For a completely degenerate electron gas the asymptotic behaviour is again proportional to a Gaussian, with a scale that is the magnetic length in this case. The prefactors are polynomial and logarithmic functions of the distance from the wall, that depend on the number of filled Landau levels $n$. As a consequence, the Gaussian asymptotic decay sets in at distances that are large compared to the magnetic length multiplied by $\sqrt{n}$.Comment: 16 pages, 2 figures, submitted to J. Phys. A: Math. Gen; corrected small typ

Solid State Physics

Contains reports on five research projects

Interaction of the Electromagnetic p-Waves with Thin Metal Films

For the first time it is shown that for thin metallic films thickness of which not exceed thickness of skin-layer, the problem allows analytical solution for arbitrary boundary value problems. The analysis of dependence of coefficients of transmission, reflection and absorbtion on angle incidence, thickness of films and coefficient of specular reflection is carried out.Comment: 15 pages, 9 figure

Heat kernel of integrable billiards in a magnetic field

We present analytical methods to calculate the magnetic response of non-interacting electrons constrained to a domain with boundaries and submitted to a uniform magnetic field. Two different methods of calculation are considered - one involving the large energy asymptotic expansion of the resolvent (Stewartson-Waechter method) is applicable to the case of separable systems, and another based on the small time asymptotic behaviour of the heat kernel (Balian-Bloch method). Both methods are in agreement with each other but differ from the result obtained previously by Robnik. Finally, the Balian-Bloch multiple scattering expansion is studied and the extension of our results to other geometries is discussed.Comment: 13 pages, Revte

Simple Analytical Particle and Kinetic Energy Densities for a Dilute Fermionic Gas in a d-Dimensional Harmonic Trap

We derive simple analytical expressions for the particle density $\rho(r)$ and the kinetic energy density $\tau(r)$ for a system of noninteracting fermions in a $d-$dimensional isotropic harmonic oscillator potential. We test the Thomas-Fermi (TF, or local-density) approximation for the functional relation $\tau[\rho]$ using the exact $\rho(r)$ and show that it locally reproduces the exact kinetic energy density $\tau(r)$, {\it including the shell oscillations,} surprisingly well everywhere except near the classical turning point. For the special case of two dimensions (2D), we obtain the unexpected analytical result that the integral of $\tau_{TF}[\rho(r)]$ yields the {\it exact} total kinetic energy.Comment: 4 pages, 4 figures; corrected versio

Quantum kinetic approach to the calculation of the Nernst effect

We show that the strong Nernst effect observed recently in amorphous superconducting films far above the critical temperature is caused by the fluctuations of the superconducting order parameter. We employ the quantum kinetic approach for the derivation of the Nernst coefficient. We present here the main steps of the calculation and discuss some subtle issues that we encountered while calculating the Nernst coefficient. In particular, we demonstrate that in the limit T=0 the contribution of the magnetization ensures the vanishing of the Nernst signal in accordance with the third law of thermodynamics. We obtained a striking agreement between our theoretical calculations and the experimental data in a broad region of temperatures and magnetic fields.Comment: 24 pages, 13 figure