Excitonic phases in a spatially separated electron-hole ladder model

TL;DR

This paper numerically investigates a one-dimensional electron-hole ladder model, revealing persistent excitonic bound states and diverse phases depending on interaction strengths, with implications for two-dimensional bilayer systems.

Contribution

It provides detailed phase diagrams of excitonic states in a 1D ladder model considering various interactions and disorder effects, advancing understanding of exciton behavior in low-dimensional systems.

Findings

Excitonic bound states are always formed at zero temperature.

System exhibits bosonic liquid or crystal phases depending on interactions.

Detailed phase diagrams with and without disorder are provided.

Abstract

We obtain the numerical ground state of a one-dimensional ladder model with the upper and lower chains occupied by spatially-separated electrons and holes, respectively. Under charge neutrality, we find that the excitonic bound states are always formed, i.e., no finite regime of decoupled electron and hole plasma exists at zero temperature. The system either behaves like a bosonic liquid or a bosonic crystal depending on the inter-chain attractive and intra-chain repulsive interaction strengths. We also provide the detailed excitonic phase diagrams in the intra- and inter-chain interaction parameters, with and without disorder. We also comment on the corresponding two-dimensional electron-hole bilayer exciton condensation.