Coexistence of insulating phases in confined fermionic chains with a Wannier-Stark potential

TL;DR

This paper investigates how a linearly varying potential in a confined fermionic chain leads to a series of coexisting insulating phases, including charge density waves, band insulators, and Mott insulators, with potential experimental implications.

Contribution

It demonstrates the coexistence of multiple insulating phases in a confined fermionic chain with a Wannier-Stark potential using advanced numerical methods.

Findings

Observation of a staircase of density plateaus indicating different insulating phases.

Identification of incommensurate regions separating these phases.

Prediction of experimental conditions to observe phase coexistence.

Abstract

We study fermions on a finite chain, interacting repulsively when residing on the same and on nearest-neighbor sites, and subjected to a Wannier-Stark linearly-varying potential. Using the density matrix renormalization-group numerical technique to solve this generalized extended Hubbard model, the ground state exhibits a staircase of (quasi) plateaus in the average local site density along the chain, decreasing from being doubly-filled to empty as the potential increases. These `plateaus' represent locked-in commensurate phases of charge density waves together with band and Mott insulators. These phases are separated by incompressible regions with incommensurate fillings. It is suggested that experimental variations of the slope of the potential and of the range of the repulsive interactions will produce such a coexistence of phases which have been individually expected theoretically and observed experimentally for uniform systems.