Competing orders and unconventional criticality in the Su-Schrieffer-Heeger model

Abstract

The phase diagram of the one-dimensional Su-Schrieffer-Heeger model of spinless fermions coupled to quantum phonons is determined by quantum Monte Carlo simulations and differs significantly from previous work. In addition to Luttinger liquid and bond-order-wave (BOW) phases, we find an extended charge-density-wave (CDW) phase. Because of different broken symmetries, BOW and CDW phases are connected by a retardation-driven phase transition. Our results are consistent with the theory of the frustrated XXZ chain, including unconventional power-law exponents at criticality, and with an interpretation in terms of deconfined quantum criticality via proliferation of solitons.