Phases and phase transitions of frustrated hard-core bosons on a triangular ladder

TL;DR

This paper investigates the phase diagram of frustrated hardcore bosons on a triangular ladder at half filling, revealing continuous and first-order phase transitions among superfluid, charge density wave, and bond ordered insulator phases.

Contribution

It provides the first detailed phase diagram of this system using DMRG, identifying new phases, transition types, and an exactly solvable point.

Findings

Identified three phases: SF, CDW, BO.

Found continuous and first-order phase transitions.

Discovered re-entrant phase transitions and an exactly solvable point.

Abstract

We study hardcore bosons on a triangular ladder at half filling in the presence of a frustrating hopping term and a competing nearest neighbor repulsion $V$ which promotes crystallization. Using the finite-size density-matrix renormalization group method, we obtain the phase diagram which contains three phases: a uniform superfluid (SF), an insulating charge density wave (CDW) crystal and a bond ordered insulator (BO). We find that the transitions from SF to CDW and SF to BO are continuous in nature, with critical exponents varying continously along the phase boundaries, while the transition from CDW to BO is found to be first order. The phase diagram is also shown to contain an exactly solvable Majumdar Ghosh point, and re-entrant SF to CDW phase transitions.