Terminable Transitions in a Topological Fermionic Ladder

TL;DR

This paper uncovers a topological connection between different Mott insulator phases in a fermionic ladder, revealing that their phase transition can be tuned from continuous to first-order, with insights from numerical and analytical methods.

Contribution

It demonstrates that D-Mott and S-Mott phases are topologically related and introduces a tunable transition order, supported by numerical simulations and an effective field theory.

Findings

D-Mott and S-Mott are topologically connected phases.

Transition order can be tuned from continuous to first-order.

Numerical and analytical methods support the topological and transition findings.

Abstract

Interacting fermionic ladders are important platforms to study quantum phases of matter, such as different types of Mott insulators. In particular, the D-Mott and S-Mott states hold pre-formed fermion pairs and become paired-fermion liquids upon doping (d-wave and s-wave, respectively). We show that the D-Mott and S-Mott phases are in fact two facets of the same topological phase and that the transition between them is terminable. These results provide a quantum analog of the well-known terminable liquid-to-gas transition. However, the phenomenology we uncover is even richer, as in contrast to the former, the order of the transition can be tuned by the interactions from continuous to first-order. The findings are based on numerical results using the variational uniform matrix-product state (VUMPS) formalism for infinite systems, and the density-matrix renormalization group (DMRG) algorithm for finite systems. This is complemented by analytical field-theoretical explanations. In particular, we present an effective theory to explain the change of transition order, which is potentially applicable to a broad range of other systems. The role of symmetries and edge states are briefly discussed.