Rashba-driven anomalous Nernst conductivity of high spin-orbit-coupled lead chalcogenide films

In the absence of external magnetization, a finite Berry curvature $\\left[\\mathrm{\\ensuremath{\\Omega}}\\left(k\\right)\\right]$ in the role of a momentum-dependent magnetic field can lead to a Hall-type thermal behavior such as the anomalous Nernst effect. The traditional and nonanomalous variants require a real-space magnetic field. In this work, we report coefficients for the anomalous Nernst effect $\\left(\\text{ANE}\\right)$ and its spin analog, a variant of the more well-established spin Nernst effect $\\left(\\text{SNE}\\right)$ in lead chalcogenide (PbX; $X$ = S, Se, Te) films. The narrow gapped PbX films with a large spin-orbit coupling (soc) offer a significant Rashba interaction that gives rise to $\\mathrm{\\ensuremath{\\Omega}}\\left(k\\right)$ and the attendant anomalous thermal behavior. In the presence of a temperature gradient, the $\\text{ANE}$ and $\\text{SNE}$ establish a thermal and spin current and are characterized by their respective coefficients which acquire higher values for a stronger Rashba interaction. We further show that an extrinsic soc generated by an in-plane electric field offers a gate-like mechanism to control (and turn-off) the anomalous thermal currents. Finally, we conclude by deriving the efficiency of an $\\text{ANE}$-driven low-temperature Carnot heat engine and demonstrate that it can be gainfully optimized in systems with a robust intrinsic soc resulting in low carrier effective masses. Cooling techniques in microdevices via $\\mathrm{\\ensuremath{\\Omega}}\\left(k\\right)$ regulated anomalous thermal conductivity contributions are briefly discussed.