Topological spin-up triplet excitonic condensation in two-dimensional electron-hole systems

TL;DR

This paper explores a novel topological phase of spin-up triplet excitonic condensation in 2D electron-hole systems, revealing unique topological properties and potential realizations in layered materials.

Contribution

It introduces the first theoretical demonstration of topological spin-up triplet excitonic condensation influenced by spin-orbit coupling and magnetic fields.

Findings

Identification of a spin-up triplet excitonic condensate with nonzero Chern number

Discovery of strong spin-polarized excitonic fluctuations before condensation

Proposal of realistic material platforms for observing this phase

Abstract

We investigate topological spin-up triplet excitonic condensation and its competition with other stabilities in a two-dimensional interacting electron-hole system taking into account Rashba spin-orbit coupling and external magnetic fields. Using an unrestricted Hartree-Fock approach, we self-consistently evaluate spin-selective excitonic condensate order parameters and the Chern number. The ground state phase diagram in the dependence on magnetic field and Coulomb interaction shows a spin-up triplet excitonic condensate (EC) with a nonzero Chern number, emerging uniquely away from the topologically trivial singlet and spin-down triplet EC regions. Strong spin-polarized triplet excitonic fluctuations preceding the condensation are further revealed through the signatures of the dynamical excitonic susceptibility spectra. Our results establish a class of topological quantum phases driven by excitonic coherence and suggest a realistic pathway to its realization in a distorted Janus monolayer of transition metal dichalcogenides or some twisted van der Waals heterostructures.