Phases of the spin-1/2 Heisenberg antiferromagnet on the diamond-decorated square lattice in a magnetic field

TL;DR

This study explores the magnetic phases of the spin-1/2 Heisenberg antiferromagnet on a diamond-decorated square lattice under a magnetic field, revealing complex phase transitions and thermodynamic behaviors through advanced computational methods.

Contribution

It provides a comprehensive analysis of the magnetic phase diagram and thermodynamic properties of the system using a combination of analytical and numerical techniques, including DMRG, exact diagonalization, and QMC.

Findings

Identification of a high-field spin-canted phase with increasing magnetization.

Discovery of a first-order quantum phase transition between ferrimagnetic and monomer-dimer phases.

Extension of the phase transition line to finite temperatures ending in Ising universality class critical points.

Abstract

The spin-1/2 Heisenberg antiferromagnet on the frustrated diamond-decorated square lattice is known to feature various zero-field ground-state phases, consisting of extended monomer-dimer and dimer-tetramer ground states as well as a ferrimagnetic regime. Using a combination of analytical arguments, density matrix renormalization group (DMRG), exact diagonalization, as well as sign-problem-free quantum Monte Carlo (QMC) calculations, we investigate the properties of this system and the related Lieb lattice in the presence of a finite magnetic field, addressing both the ground-state phase diagram as well as several thermodynamic properties. In addition to the zero-field ground states, we find at high magnetic field a spin-canted phase with a continuously rising magnetization for increasing magnetic field strength, as well as the fully polarized paramagnetic phase. At intermediate field strength, we identify a first-order quantum phase transition line between the ferrimagnetic and the monomer-dimer regime. This first-order line extends to finite temperatures, terminating in a line of critical points that belong to the universality class of the two-dimensional Ising model.