Floquet-driven thermal transport in topological Haldane lattice systems

TL;DR

This study explores how off-resonant circularly polarized light influences topological phases and induces spin- and valley-dependent anomalous Nernst effects in 2D Haldane lattice systems, revealing tunable thermoelectric responses.

Contribution

It demonstrates electrically and optically tunable topological phases and identifies conditions for generating pure valley and spin Nernst currents in 2D materials.

Findings

Finite charge Nernst conductivity under optical driving and spin-orbit coupling.

Pure valley Nernst current requires sublattice asymmetry and off-resonant light.

Temperature signatures reveal topological phase transitions.

Abstract

In this paper, we employ a modified Haldane lattice model to investigate the light-driven, spin- and valley-dependent anomalous Nernst effect in two-dimensional hexagonal topological systems. We demonstrate that two-dimensional buckled materials exhibit a hierarchy of electrically and optically tunable topological phases when subjected to off-resonant circularly polarized light in the presence of intrinsic spin-orbit coupling and a staggered sublattice potential. Within a Berry-curvature-driven transport framework, we systematically analyze charge-, spin-, and valley-resolved anomalous Nernst responses and identify their correspondence with distinct topological regimes. A finite charge Nernst conductivity arises under optical driving combined with spin-orbit coupling, whereas the generation of a pure valley Nernst current requires the simultaneous presence of sublattice asymmetry and off-resonant light. Substrate-induced inversion asymmetry further enables thermally driven valley currents with tunable magnitude and sign. We find that single-spin and single-valley Nernst responses occur in selected insulating and metallic phases, while the valley Nernst signal is suppressed in spin-polarized and anomalous quantum Hall phases. Extending our analysis to monolayer MoS$_2$, we show that strong spin-orbit coupling and broken inversion symmetry allow fully spin- and valley-polarized Nernst currents over a broad energy window. The temperature dependence of the Nernst response exhibits characteristic signatures of topological phase transitions, establishing the anomalous Nernst effect as a sensitive probe of field-engineered band topology in two-dimensional Dirac materials.