Continuously varying critical exponents in an exactly solvable long-range cluster XY mode

TL;DR

This paper analyzes a solvable long-range cluster XY model, revealing how critical exponents and entanglement entropy vary with interaction decay, providing new insights into quantum criticality in long-range systems.

Contribution

It introduces an exactly solvable long-range cluster XY model and characterizes how its critical exponents depend on the decay parameter, extending understanding of long-range quantum phase transitions.

Findings

Critical exponents $ u$ and $z$ depend on decay exponent $eta$

The relation $ u z = 1$ holds across parameters

Entanglement entropy varies with $eta$, indicating changing central charge

Abstract

We investigate a generalized antiferromagnetic cluster XY model in a transverse magnetic field, where long-range interactions decay algebraically with distance. This model can be exactly solvable within a free fermion framework. By analyzing the gap, we explicitly derive the critical exponents $\nu$ and $z$, finding that the relationship $\nu z = 1$ still holds. However, the values of $\nu$ and $z$ depend on the decaying exponent $\alpha$, in contrast to those for the quantum long-range antiferromagnetic Ising chain. To optimize scaling behavior, we verify these critical exponents using correlation functions and fidelity susceptibility, achieving excellent data collapse across various system sizes by adjusting fitting parameters. Finally, we compute the entanglement entropy at the critical point to determine the central charge $c$, and find it also varies with $\alpha$. This study provides insights into the unique effect of long-range cluster interactions on the critical properties of quantum spin systems.