On effects of regular S=1 dilution of S=1/2 antiferromagnetic Heisenberg chains by a quantum Monte Carlo simulation

TL;DR

This study uses quantum Monte Carlo simulations to explore how regular S=1 dilution affects the ground states of S=1/2 antiferromagnetic chains, revealing alternating magnetic phases and a gap dependence on dilution concentration.

Contribution

It provides the first detailed numerical analysis of the phase transitions and gap behavior in diluted S=1/2 chains with regular S=1 impurities.

Findings

Two distinct ground-state phases identified: ferrimagnetic and non-magnetic.

The ferrimagnetic phase has a gapless spectrum and weakens with dilution.

The non-magnetic phase exhibits a gap that scales with the square root of dilution concentration.

Abstract

The effects of regular S=1 dilution of S=1/2 isotropic antiferromagnetic chain are investigated by the quantum Monte Carlo loop/cluster algorithm. Our numerical results show that there are two kinds of ground-state phases which alternate with the variation of $S^1=1$ concentration. When the effective spin of a unit cell is half-integer, the ground state is ferrimagnetic with gapless energy spectrum and the magnetism becomes weaker with decreasing of the $S^1$ concentration $\rho = 1/M$. While it is integer, a non-magnetic ground state with gaped spectrum emerges and the gap gradually becomes narrowed as fitted by a relation of $\Delta \approx 1.25\sqrt{\rho}$.