Striped Spin Density Wave in a Graphene/Black Phosphorous Heterostructure

TL;DR

This study investigates a graphene-black phosphorus heterostructure, revealing a tunable striped spin density wave phase with a metal-insulator transition, supported by a tight-binding model and mean-field analysis, with potential experimental signatures.

Contribution

It introduces a detailed tight-binding model for G/BP heterostructure and predicts a tunable striped SDW phase with a complex phase diagram, advancing understanding of emergent electronic phases in moiré systems.

Findings

Discovery of a striped SDW order in G/BP heterostructure.

Identification of a gate-tunable metal-insulator transition.

Prediction of anisotropic collective excitations affecting transport.

Abstract

A bilayer formed by stacking two distinct materials creates a moir\'e lattice, which can serve as a platform for novel electronic phases. In this work we study a unique example of such a system: the graphene-black phosphorus heterostructure (G/BP), which has been suggested to have an intricate band structure. Most notably, the valence band hosts a quasi-one-dimensional region in the Brillouin zone of high density of states, suggesting that various many-body electronic phases are likely to emerge. We derive an effective tight-binding model that reproduces this band structure, and explore the emergent broken-symmetry phases when interactions are introduced. Employing a mean-field analysis, we find that the favored ground-state exhibits a striped spin density wave (SDW) order, characterized by either one of two-fold degenerate wave-vectors that are tunable by gating. Further exploring the phase-diagram controlled by gate voltage and the interaction strength, we find that the SDW-ordered state undergoes a metal to insulator transition via an intermediate metallic phase which supports striped SDW correlations. Possible experimental signatures are discussed, in particular a highly anisotropic dispersion of the collective excitations which should be manifested in electric and thermal transport.