Correlated phases of moat-band excitons in two dimensions

Abstract

We study dilute two-dimensional systems of interacting excitons with a moat dispersion, whose ground-state manifold consists of a set of discrete or continuously degenerate energy minima. At low densities and in the presence of contact interactions, it is known that the bosons can undergo statistical transmutation and give rise to a chiral spin liquid. Here, we show that long-range interactions such as those expected in excitonic systems introduce a rich competition between the chiral spin liquid and different kinds of Bose-Einstein condensates. The moat dispersion can favor Bose-Einstein condensation into states occupying multiple momenta, leading to inhomogeneous and supersolid phases with a highly anisotropic superfluid response. We demonstrate that a proper $T$-matrix renormalization of the exciton-exciton interaction is essential for describing these phases and show that they can arise even from purely repulsive interactions. This formalism is employed to obtain the phase diagram of competing homogeneous and stripe condensates with the chiral spin liquid in an electron-hole bilayer model. In addition, we show how the $T$ matrix enters the familiar Gross-Pitaevskii framework and map out extended phase diagrams within a pseudopotential approximation. We place our findings in the context of real excitonic systems by discussing the roles of finite lifetimes, disorder, band-structure warping, and nonzero temperatures. We conclude that moat bands can drive Bose-Einstein condensation and supersolidity already at weak coupling, in contrast to the case of a standard parabolic dispersion.

Final published version. 26 pages, 11 figures

References in corpus (27)

• Degenerate Quantum Gases with Spin-Orbit Coupling
• High-temperature superfluidity with indirect excitons in van der Waals heterostructures
• Fulde-Ferrell-Larkin-Ovchinnikov State in Heavy Fermion Superconductors
• Correlated insulator of excitons in WSe2/WS2 moiré superlattices
• Stability of ultracold atomic Bose condensates with Rashba spin-orbit coupling against quantum and thermal fluctuations
• Composite fermion state of spin-orbit coupled bosons
• Wigner supersolid of excitons in electron-hole bilayers
• Towards superfluidity of dipolar excitons in a TMDC double layer
• Spontaneous formation of a non-uniform chiral spin liquid in moat-band lattices
• Excitonic topological order in imbalanced electron-hole bilayers
• Moiré-Bose-Hubbard model for interlayer excitons in twisted transition metal dichalcogenide heterostructures
• Excitonic Mott insulator in a Bose-Fermi-Hubbard system of moiré ${\mathrm{WS}}_2$/${\mathrm{WSe}}_2$ heterobilayer
• Evidence for Exciton Crystals in a 2D Semiconductor Heterotrilayer
• Chester supersolid of spatially indirect excitons in double-layer semiconductor heterostructures
• Interaction-driven transport of dark excitons in 2D semiconductors with phonon-mediated optical readout
• Mott-moiré excitons
• Excitons in the Fractional Quantum Hall Effect
• Strong-coupling phases of trions and excitons in electron-hole bilayers at commensurate densities
• Exploring quantum quasicrystal patterns: a variational study
• Chiral spin liquid state of strongly interacting bosons with a moat dispersion: a Monte Carlo simulation
• Susceptibility indicator for chiral topological orders emergent from correlated fermions
• Self-induced Bose glass phase in quantum cluster quasicrystals
• Striped excitonic (super)solid in anisotropic semiconductors with screened exciton interactions
• Moiré excitons in generalized Wigner crystals
• Long-range spatial extension of exciton states in van der Waals heterostructure
• Variational and field-theoretical approach to exciton-exciton interactions and biexcitons in semiconductors
• Superfluid Fraction of a 2D Bose-Einstein Condensate in a Triangular Lattice