Many-body Multifractality throughout Bosonic Superfluid and Mott Insulator Phases

TL;DR

This paper investigates the many-body multifractality of the Bose-Hubbard model's ground state across superfluid and Mott insulator phases, revealing how fractal dimensions signal phase transitions even in small systems.

Contribution

It introduces a novel approach using generalized fractal dimensions to identify and analyze the superfluid to Mott insulator transition in the Bose-Hubbard model.

Findings

Generalized fractal dimensions signal the Mott insulator transition.

Scaling of the derivative of fractal dimensions estimates the critical point.

Single wavefunction amplitude characterizes the transition quantitatively.

Abstract

We demonstrate many-body multifractality of the Bose-Hubbard Hamiltonian's ground state in Fock space, for arbitrary values of the interparticle interaction. Generalized fractal dimensions unambiguously signal, even for small system sizes, the emergence of a Mott insulator, that cannot, however, be naively identified with a localized phase in Fock space. We show that the scaling of the derivative of any generalized fractal dimension with respect to the interaction strength encodes the critical point of the superfluid to Mott insulator transition, and provides an efficient way to accurately estimate its position. We further establish that the transition can be quantitatively characterized by one single wavefunction amplitude from the exponentially large Fock space.