Quantum Geometric Entropy Production and Entropy Hall Effect

Quantum geometry, encoded in the Berry curvature and quantum metric, has unified diverse anomalous transport phenomena in solids, yet a microscopic quantum-geometric theory of entropy transport for Bloch electrons is still lacking. We formulate an entropy continuity equation for noninteracting fermions driven by an electric field, starting from the von Neumann entropy, and obtain quantum-mechanical expressions for the entropy current density and entropy production rate. Introducing relaxation through a relaxation-time dissipator, we identify the quantum metric as the origin of the leading entropy production, providing a direct microscopic diagnostic of dissipation in both the extrinsic Drude response and an intrinsic nonlinear Ohmic contribution controlled by quantum metric. We further predict an entropy Hall effect arising from the Berry curvature and show that it obeys an Onsager reciprocal relation with the anomalous Nernst effect under a temperature gradient. Finally, we establish universal relations connecting entropy and charge currents under DC and AC driving, offering experimentally accessible probes of quantum geometry through nonequilibrium entropy flow.

💡 Research Summary

The paper develops a fully quantum‑mechanical theory of entropy transport for non‑interacting Bloch electrons driven by an external electric field. Starting from the von Neumann entropy operator ˆs = − ˆρ ln ˆρ − (1−ˆρ) ln(1−ˆρ), the authors derive an entropy continuity equation ∂t s + ∇·js = Σ, where the source term Σ is determined by a dissipator that models relaxation processes. By introducing a relaxation‑time approximation (RTA) dissipator D