Phase diagram of strongly interacting bilayer electron systems at rs ≈ 10–20

Determine the phase diagram of two-dimensional electron systems in the strongly interacting regime r_s ≈ 10–20 relevant to MoS2 homobilayers, including the nature and boundaries of phases between Fermi liquid and crystalline (Wigner crystal) states.

Background

MoS2 homobilayers naturally realize large interaction parameters (r_s ~ 10–20) due to large effective mass and low dielectric constant, placing the system in a regime between conventional Fermi liquid and crystalline electron states. Understanding this regime is crucial for interpreting observed optical signatures and for guiding searches for correlated phases such as interlayer coherence and superfluidity.

The authors note that theoretical understanding is limited, with only sparse Monte Carlo data, underscoring the need for a systematic phase-diagram determination in this parameter range.

References

Experimentally, the challenge lies in controllably entering and probing a strongly-interacting regime, while theoretically, the phase diagram for $r_s\simeq 10 - 20$ (as in our experiment), where the electronic system is between a simple Fermi liquid and crystalline states, is not yet fully understood, with only limited Monte Carlo data.

— Optical signatures of interlayer electron coherence in a bilayer semiconductor  (2409.08329 - Liu et al., 2024) in Main text, paragraph beginning 'Our observations open up exciting opportunities...' (closing discussion)

However, much is still unknown about the transition even in the absence of Berry curvature, including the nature of any intermediate states.

— The influence of quantum geometry on the phase boundary and collective excitations of electron liquids and crystals  (2609.04330 - Froese et al., 3 Sep 2026) in Section 1, Introduction

Whether the Pomeranchuk effect can emerge in this regime remains unknown.

— Observation of the electronic Pomeranchuk effect in generalized Wigner crystals of twisted MoS$_2$  (2609.30788 - Fang et al., 25 Sep 2026) in Introduction