Fragile Mott Insulators

TL;DR

This paper introduces 'fragile Mott insulators,' a new class of insulators that cannot be smoothly transformed into band insulators without breaking symmetries, characterized by specific point-group representations.

Contribution

It proves the existence of fragile Mott insulators and provides explicit examples, expanding the understanding of symmetry-protected insulating phases.

Findings

Fragile Mott insulators are not adiabatically connected to band insulators under certain symmetries.

Different fragile Mott insulators are distinguished by nontrivial point-group representations.

Examples include the d-Mott insulator in the checkerboard Hubbard model and the AKLT insulator.

Abstract

We prove that there exists a class of crystalline insulators, which we call "fragile Mott insulators" which are not adiabatically connected to any sort of band insulator provided time-reversal and certain point-group symmetries are respected, but which are otherwise unspectacular in that they exhibit no topological order nor any form of fractionalized quasiparticles. Different fragile Mott insulators are characterized by different nontrivial one-dimensional representations of the crystal point group. We illustrate this new type of insulators with two examples: the d-Mott insulator discovered in the checkerboard Hubbard model at half-filling and the Affleck-Kennedy-Lieb-Tasaki insulator on the square lattice.