The Electronic States of Two Oppositely doped Mott Insulators Bilayers

TL;DR

This paper investigates the effects of Coulomb interactions between oppositely doped Mott insulator bilayers, revealing exciton formation, condensation, and novel phases like an insulating spin liquid, with implications for complex oxide interfaces.

Contribution

It introduces a bilayer model showing how inter-layer interactions induce exciton formation and novel phases, extending understanding beyond single-layer systems.

Findings

Charge neutral electron-hole pairs form in 1D with any interaction strength.

Inter-layer excitons form and condense in 2D, leading to new phases.

Emergence of an insulating spin liquid phase in bilayer systems.

Abstract

We study the effect of Coulomb interaction between two oppositely doped low-dimensional tJ model systems. We exactly show that, in the one-dimensional case, an arbitrarily weak interaction leads to the formation of charge neutral electron-hole pairs. We then use two different mean-field theories to address the two-dimensional case, where inter-layer excitons also form and condense. We propose that this results in new features which have no analog in single layers, such as the emergence of an insulating spin liquid phase. Our simple bilayer model might have relevance to the physics of doped Mott insulator interfaces and of the new four layer Ba2CaCu4O8 compound.