U(1) symmetry breaking in one-dimensional Mott insulator studied by the Density Matrix Renormalization Group method

TL;DR

This paper investigates U(1) symmetry breaking in one-dimensional Mott insulators using the Density Matrix Renormalization Group method, revealing charge fluctuations and quantum phase transitions induced by external fields.

Contribution

It introduces a novel study of particle number non-conserving external fields in 1D strongly correlated systems with DMRG, highlighting symmetry-breaking effects and phase transitions.

Findings

Ground state exhibits particle number fluctuations due to symmetry breaking.

Charge fluctuations persist even at half-filling with finite effective fields.

Identification of a quantum phase transition driven by symmetry-breaking fields.

Abstract

A new type of external fields violating the particle number preservation is studied in one-dimensional strongly correlated systems by the Density Matrix Renormalization Group method. Due to the U(1) symmetry breaking, the ground state has fluctuation of the total particle number, which implies injection of electrons and holes from out of the chain. This charge fluctuation can be relevant even at half-filling because the particle-hole symmetry is preserved with the finite effective field. In addition, we discuss a quantum phase transition obtained by considering the symmetry-breaking fields as a mean field of interchain-hopping.