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

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.

Automated summary

The study focuses on the characteristics of disorder operators across a continuous quantum phase transition in (2 + 1)d, specifically at a conformally invariant critical point with U(1) symmetry. It shows analytically the power-law scaling behavior of the disorder operator with a small U(1) rotation angle defined on a rectangle region, and confirms the presence of universal corner correction through systematic computational and numerical simulations. The exponent of the corner term determined from simulations aligns well with the analytical predictions.