Quantum-geometry-driven Mott transitions and magnetism

TL;DR

This paper demonstrates that quantum geometry of Bloch bands can drive Mott insulator transitions and magnetic order changes, providing a new mechanism beyond traditional bandwidth control, with implications for multi-orbital and moiré materials.

Contribution

It introduces quantum geometry as a mechanism for Mott and magnetic transitions, studied through the Kane-Mele-Hubbard model with exact diagonalization.

Findings

Quantum geometry influences Mott transitions and magnetic order.

Quantum geometric properties can tune Mott insulator states.

Non-local Coulomb scattering explains the transitions.

Abstract

Quantum geometry quantifies how the single-particle Bloch wavefunction changes in phase and amplitude across the Brillouin Zone. In multi-orbital systems where bands have strongly mixed orbital composition, quantum geometry plays a vital role in determining the ground state and low-energy properties of interacting electronic systems. In this work, we show that Mott metal-insulator transitions, as well as transitions between different magnetic orders within the Mott insulating phase, can be driven by the quantum geometry of the underlying Bloch band, thereby providing a mechanism complementary to conventional bandwidth-tuned Mott transitions. By studying the Kane-Mele-Hubbard model using exact diagonalization, we demonstrate that in in half-filled and topologically-trivial bands, quantum geometric properties of the Bloch states alone can act as a tuning knob for Mott metal-to-insulator and affect the competition between ferromagnetism and antiferromagnetism. We show that both transitions may be heuristically understood via non-local Coulomb scattering in a basis of exponentially localized Wannier functions. These results highlight the role of quantum geometry beyond topological settings as a governing principle for conventional Mott and magnetic physics in multi-orbital and moir\'e materials.