Regular Article

Multicritical behavior of the fidelity susceptibility for the 2D quantum transverse-field XY model

Department of Physics, Faculty of Science, Okayama University, Okayama 700-8530, Japan

^a e-mail: nisiyama@psun.phys.okayama-u.ac.jp

Received: 22 May 2019
Received in final form: 6 June 2019
Published online: 5 August 2019

Abstract

The two-dimensional quantum XY model with a transverse magnetic field was investigated with the exact diagonalization method. Upon turning on the magnetic field h and the XY -plane anisotropy η, there appear a variety of phase boundaries, which meet at the multicritical point (h, η) = (2, 0). We devote ourselves to the Ising-universality branch, placing an emphasis on the multicritical behavior. As a probe to detect the underlying phase transitions, we adopt the fidelity susceptibility χ_F. The fidelity susceptibility does not rely on any presumptions as to the order parameter involved. We made a finite-size-scaling analysis of χ_F for η = 1 (Ising limit), where a number of preceding results are available. Thereby, similar analyses with η scaled were carried out around the multicritical point. We found that the χ_F data are described by the crossover scaling theory. A comparison with the preceding studies of the multicriticality is made.