Static Transport Properties Research Articles

Universal density shift coefficients for the thermal conductivity and shear viscosity of a unitary Fermi gas

We measure universal temperature-independent density shifts for the thermal conductivity κT and shear viscosity η, relative to the high temperature limits, for a normal phase unitary Fermi gas confined in a box potential. We show that a time-dependent kinetic theory model enables extraction of the hydrodynamic transport times τη and τκ from the time-dependent free decay of a spatially periodic density perturbation, yielding the static transport properties and density shifts, corrected for finite relaxation times. Published by the American Physical Society 2024

Static transport properties of random alloys: Vertex corrections in conserving approximations

The theoretical formulation and numerical evaluation of the vertex corrections in multiorbital techniques of theories of electronic properties of random alloys are analyzed. It is shown that current approaches to static transport properties within the so-called conserving approximations lead to the inversion of a singular matrix as a direct consequence of the Ward identity relating the vertex corrections to one-particle self-energies. We propose a simple removal of the singularity for quantities (operators) with vanishing average values for electron states at the Fermi energy, such as the velocity or the spin torque; the proposed scheme is worked out in detail in the self-consistent Born approximation and the coherent-potential approximation. Applications involve calculations of the residual resistivity for various random alloys, including spin-polarized and relativistic systems, treated on an ab initio level, with particular attention paid to the role of different symmetries (inversion of space and time).

The Influence of Dynamical Screening on the Transport Properties of Dense Plasmas

AbstractWe investigate the effects of dynamical screening on the static transport properties. We review the low density expansion for the electron‐electron and electron‐ion correlation functions and give results for a 6‐moment approach within linear response theory. The expansion coefficients are given. The convergence of thermoelectric transport coefficients is examined in dependence of the rank of the collision term determinant. The results are compared with previous calculations and experiments. Effective Debye screening radii derived from the Gould‐DeWitt scheme for the inclusion of strong collisions as well as dynamical effects are discussed. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Static and dynamic transport study of β-FeSi 2 single crystals

Static transport properties and transient thermoelectric effect (TTE) of β-FeSi 2 single crystals, which has received considerable attention as optical and thermoelectric devices, have been measured. The Hall and TTE data clearly showed the existence of multiple conduction carriers. From these results, the tentative band scheme is discussed.

Dynamical study of the transport properties of eta -Mo4O11 single crystals by use of the photoinduced transient thermoelectric effect.

The pulsed-laser-induced transient thermoelectric effect (TTE) and the static transport properties (resistivity, Hall coefficient, magnetoresistance, and thermopower) of a quasi-two-dimensional \ensuremath{\eta}-${\mathrm{Mo}}_{4}$${\mathrm{O}}_{11}$ crystal have been measured over the time range 50 ns--2 ms and temperature range 4.2--300 K. The observed TTE voltages decay exponentially with time, showing relaxation processes with multiple relaxation times ${\mathrm{\ensuremath{\tau}}}_{\mathit{i}}$ (i=1--5) for thermal diffusions of photogenerated carriers (electrons and holes), from which we can evaluate the corresponding carrier mobilities ${\mathrm{\ensuremath{\mu}}}_{\mathit{i}}$. The temperature dependences of both dynamic and static transport quantities show anomalies around the characteristic temperatures ${\mathit{T}}_{\mathit{c}1}$=105 K and ${\mathit{T}}_{\mathit{c}2}$=35 K; ${\mathit{T}}_{\mathit{c}1}$ is the well-known charge-density-wave (CDW) transition temperature, but for the latter no definitive x-ray evidence for a CDW transition is reported. However, using our dynamic data and the existing two-dimensional tight-binding model, together with our proposed nesting model of the Fermi surfaces and the CDW-related modifications of the electron and hole bands at ${\mathit{T}}_{\mathit{c}1}$ and ${\mathit{T}}_{\mathit{c}2}$, we have self-consistently calculated the temperature dependence of the dc transport quantities, in satisfactory agreement with the experiments.