Magnetothermopower study of the charge density wave state in a multiband organic conductor α - (BEDT - TTF)_2KHg(SCN)_4

摘要

Magnetic field dependence of the thermopower and Nernst effect of the multiband organic conductor α - (BEDT - TTF)_2KHg(SCN)_4 is theoretically studied at low temperatures in the charge density wave (CDW) state, to fields of 30 T and several field directions. A theoretical model of quantum interlayer tunneling for the q1D charge carriers is used to probe the thermoelectric effects in the CDW state. The contribution from the q2D carriers is calculated by using the Boltzmann transport theory. The background components of the thermopower and Nernst effect as well as the quantum oscillations that originate from the closed Fermi surface orbits are analyzed. The model implies that in the CDW state, the properties of α - (BEDT - TTF)_2KHg(SCN)_4 are determined mostly by the orbits on the new open Fermi sheets. This is in accord with the previously reported CDW scenario of the low temperature state of α - (BEDT - TTF)_2KHg(SCN)_4 with imperfect nesting of the open Fermi surface sections.