Crossover behavior of the J1-J2 model in a staggered magnetic field

TL;DR

This paper investigates the phase crossover in the J1-J2 Heisenberg chain under a staggered magnetic field, revealing the transition from Gaussian to Ising fixed point behavior through numerical methods.

Contribution

It provides a numerical analysis of the crossover from Gaussian to Ising fixed points in the J1-J2 model under a staggered magnetic field, highlighting the critical behavior.

Findings

Identification of the massless flow between fixed points

Numerical determination of excitation gaps

Finite-size scaling confirming criticality

Abstract

The ground states of the $S=\frac12$ Heisenberg chain with the nearest-neighbor and the next-nearest-neighbor antiferromagnetic couplings are numerically investigated in a staggered magnetic field. While the staggered magnetic field may induce the N\'eel-type excitation gap, and it is characterized by the Gaussian fixed point in the spin-fluid region, the crossover to the behavior controlled by the Ising fixed point is expected to be observed for the spontaneously dimerized state at finite field. Treating a low-lying excitation gap by the phenomenological renormalization-group method, we numerically determine the massless flow connecting the Gaussian and Ising fixed points. Further, to check the criticalities, we perform the finite-size-scaling analysis of the excitation gap.