Dirac and chiral spin liquids on spin-1/2 square-lattice Heisenberg antiferromagnet

TL;DR

This paper provides evidence that the ground state of the spin-1/2 J1-J2 Heisenberg antiferromagnet on a square lattice is a Z2 Dirac spin liquid, using advanced numerical and analytical methods, and explores topological phase transitions involving chiral spin liquids.

Contribution

It combines Gutzwiller-guided DMRG with analytical analysis to identify the Z2 Dirac spin liquid as the ground state and investigates topological transitions with chiral spin liquids.

Findings

Ground state is a Z2 Dirac spin liquid.

Transition from Z2 chiral to U(1)2 chiral spin liquid with increasing J_χ.

Efficient description via Gutzwiller-projected parton theory.

Abstract

We revisit the challenging problem of identifying the quantum spin liquid candidate in the spin-1/2 $J_1$-$J_2$ Heisenberg antiferromagnet on the square lattice. By integrating the Gutzwiller-guided density matrix renormalization group method with analytical analyses, we present clear evidence that the ground state is a Z$_2$ Dirac spin liquid. This state can be efficiently described by a Gutzwiller-projected parton theory characterized by its projective symmetry group. To distinguish the difference between the projected Z$_2$ and U(1) parton state, we investigate the chiral spin liquid ground states as topological orders by incorporating a $J_\chi$ term into the $J_1$-$J_2$ model and observe a transition from a Z$_2$ chiral spin liquid to a U(1)$_2$ chiral spin liquid as $J_\chi$ increases.