Andrei A. Varlamov | Searcharxiv

arXiv2011

Giant Nernst-Ettingshausen oscillations in Semiclassically strong magnetic fields

We consider the Nernst-Ettingshausen (NE) effect in the presence of semiclassically strong magnetic fields for a quasi-two dimensional system with a parabolic or linear dispersion of carriers. We show that the occurring giant oscillations of the NE coefficient are coherent with the recent experimental observation in graphene, graphite and bismuth. In the 2D case we find the exact shape of these oscillations and show that their magnitude decreases/increases with enhancement of the Fermi energy for Dirac fermions/normal carriers. With a crossover to 3D spectrum the phase of oscillations shifts, their amplitude decreases and the peaks become asymmetric.

cond-mat.mes-hall↗

arXiv1996

The Fluctuation Induced Pseudogap in the Infrared Optical Conductivity of High Temperature Superconductors

We study the effect of fluctuations on the {\bf ac} conductivity of a layered superconductor both for $c$-axis and $ab$-plane electromagnetic wave polarizations. The fluctuation contributions of different physical nature and signs (paraconductivity, Maki-Thompson anomalous contribution, one-electron density of states renormalization) are found to be suppressed by the external field at different characterisitic frequencies ($ ω_{\rm AL}\sim T-T_{\rm c}$, $ω_{\rm MT} \sim \max\{ T-T_{\rm c}, τ_φ^{-1}\}$, $ ω_{\rm DOS} \sim \min\{T,τ^{-1}\}$ for the $2D$ case). As a result the appearance of the nonmonotonic frequency dependence (pseudogap) in the infrared optical conductivity of HTS film is predicted. The effect has to be especially pronounced in the case of the electromagnetic field polarization along $c$-axis.

supr-con↗