Dimerization tendencies of the pyrochlore Heisenberg antiferromagnet: A functional renormalization group perspective

TL;DR

This study uses advanced renormalization group techniques to explore the ground state of the pyrochlore Heisenberg antiferromagnet, revealing tendencies toward lattice symmetry breaking and supporting the monopole spin liquid state.

Contribution

It introduces an improved pseudofermion functional renormalization group method that addresses technical issues and applies it to analyze symmetry breaking and spin liquid states in the pyrochlore lattice.

Findings

Lattice symmetry breaking tendencies in the ground state.

Monopole spin liquid state shows strongest support among tested ans"atze.

Ground state likely exhibits broken $C_3$ or inversion symmetry.

Abstract

We investigate the ground state properties of the spin-$1/2$ pyrochlore Heisenberg antiferromagnet using pseudofermion functional renormalization group techniques. The first part of our analysis is based on an enhanced parton mean-field approach which takes into account fluctuation effects from renormalized vertex functions. Our implementation of this technique extends earlier approaches and resolves technical difficulties associated with a diagrammatic overcounting. Using various parton ans\"atze for quantum spin liquids, dimerized and nematic states our results indicate a tendency for lattice symmetry breaking in the ground state. While overall quantum spin liquids seem unfavorable in this system, the recently proposed monopole state still shows the strongest support among all spin liquid ans\"atze that we have tested, which is further confirmed by our complementary variational Monte Carlo calculations. In the second part of our investigation, we probe lattice symmetry breaking more directly by applying the pseudofermion functional renormalization group to perturbed systems. Our results from this technique confirm that the system's ground state either exhibits broken $C_3$ rotation symmetry, or a combination of inversion and $C_3$ symmetry breaking.