Fig. 1: Concept of mixed-dimensionality for transverse thermoelectrics.
From: Large transverse thermoelectric effect induced by the mixed-dimensionality of Fermi surfaces
In the longitudinal (a) and transverse (b, c) thermoelectric effects, the electric field E appears parallel and perpendicular to the temperature gradient − ∇ T, respectively. b Ordinary and anomalous Nernst effects induced by the external magnetic field H or magnetization M. c Transverse thermoelectric effect in p × n-type (goniopolar) conductor. Temperature gradient is applied to a direction rotated from the crystallographic axis. Owing to the opposite polarities for each axis, the electric field is induced along the transverse direction. d Schematic illustration of the mixed-dimensional Fermi surfaces. Two large Fermi surfaces, a one-dimensional (1D) hole sheet with a normal vector along the c-axis and a two-dimensional (2D) electron cylinder with a normal vector along the ab-planes direction, are considered. As a result of these combinations, though hybridization should occur at the crossing points, a goniopolar metal with positive c-axis thermopower (Scc > 0) and negative in-plane thermopower (Saa < 0) may be obtained.
