Scaling of disorder operator at $(2+1)d$ U(1) quantum criticality

TL;DR

This paper investigates the universal scaling behavior of the disorder operator at a (2+1)d U(1) quantum critical point, revealing a perimeter law with corner corrections and confirming predictions through large-scale quantum Monte Carlo simulations.

Contribution

It analytically derives the universal power-law scaling of the disorder operator at a U(1) critical point and verifies it numerically in the Bose-Hubbard model.

Findings

Disorder operator exhibits perimeter law scaling with corner corrections.

Analytical formula for corner exponent near smooth corners.

Numerical results agree with analytical predictions.

Abstract

We study disorder operator, defined as a symmetry transformation applied to a finite region, across a continuous quantum phase transition in $(2+1)d$. We show analytically that at a conformally-invariant critical point with U(1) symmetry, the disorder operator with a small U(1) rotation angle defined on a rectangle region exhibits power-law scaling with the perimeter of the rectangle. The exponent is proportional to the current central charge of the critical theory. Such a universal scaling behavior is due to the sharp corners of the region and we further obtain a general formula for the exponent when the corner is nearly smooth. To probe the full parameter regime, we carry out systematic computation of the U(1) disorder parameter in the square lattice Bose-Hubbard model across the superfluid-insulator transition with large-scale quantum Monte Carlo simulations, and confirm the presence of the universal corner correction. The exponent of the corner term determined from numerical simulations agrees well with the analytical predictions.