Phase transitions in the spin-1/2 Heisenberg antiferromagnet on the dimerized diamond lattice

TL;DR

This study explores quantum and thermal phase transitions in a spin-1/2 Heisenberg model on a dimerized diamond lattice, identifying the quantum critical point and comparing theoretical approaches with quantum Monte Carlo results.

Contribution

It combines quantum Monte Carlo simulations with a decoupled dimer mean-field theory to analyze phase transitions and accurately determine the critical coupling ratio in a three-dimensional quantum magnet.

Findings

Quantum disordered ground state at strong dimerization.

Critical interdimer to intradimer coupling ratio: 0.3615(5).

Decoupled dimer mean-field captures the competition between singlet formation and magnetic order.

Abstract

Using a combination of unbiased quantum Monte Carlo simulations and a decoupled dimer mean-field theory, we investigate the thermal and quantum phase transitions of the spin-1/2 Heisenberg model on the dimerized diamond lattice. We find that at sufficiently strong dimerization the system exhibits a quantum disordered ground state, in contrast to the antiferromagnetic phase stabilized at weak dimerization. We determine the quantum critical point and examine the thermodynamic responses in both regimes. The ratio for the critical interdimer ($J_c$) to intradimer ($J_D$) coupling is obtained as $J_c/J_D = 0.3615(5)$. Our results show that the decoupled dimer mean-field theory well captures the competition between the local singlet formation and the antiferromagnetic ordering tendency, and thus provides an appropriate qualitative description of this three-dimensional quantum magnet, in contrast to the conventional mean-field decoupling. We also examine the differences in the ordering temperatures between the antiferromagnetic and the ferromagnetic spin-1/2 Heisenberg model on the diamond lattice based on quantum Monte Carlo simulations.