# Quantum phases and topological properties of interacting fermions in one-dimensional superlattices

## TL;DR

This paper explores the topological phases and quantum phase transitions of interacting fermions in one-dimensional superlattices, revealing how topological invariants change across different insulating phases, with implications for quantum-gas experiments.

## Contribution

It introduces a comprehensive analysis of topological and quantum phase transitions in interacting fermionic superlattices, including Chern number calculations in a many-body context.

## Key findings

- Identification of phase transitions from band insulator to other insulating phases.
- Calculation of Chern numbers showing topological transitions.
- Potential observability of these properties in quantum-gas experiments.

## Abstract

The realization of artificial gauge fields in ultracold atomic gases has opened up a path towards experimental studies of topological insulators and, as an ultimate goal, topological quantum matter in many-body systems. As an alternative to the direct implementation of two-dimensional lattice Hamiltonians that host the quantum Hall effect and its variants, topological charge-pumping experiments provide an additional avenue towards studying many-body systems. Here, we consider an interacting two-component gas of fermions realizing a family of one-dimensional superlattice Hamiltonians with onsite interactions and a unit cell of three sites, whose groundstates would be visited in an appropriately defined charge pump. First, we investigate the grandcanonical quantum phase diagram of individual Hamiltonians, focusing on insulating phases. For a certain commensurate filling, there is a sequence of phase transitions from a band insulator to other insulating phases (related to the physics of ionic Hubbard models) for some members of the manifold of Hamiltonians. Second, we compute the Chern numbers for the whole manifold in a many-body formulation and show that, related to the aforementioned quantum phase transitions, a topological transition results in a change of the value and sign of the Chern number. We provide both an intuitive and conceptual explanation and argue that these properties could be observed in quantum-gas experiments.