Spontaneous Chiral-Spin Ordering in Spin-Orbit Coupled Honeycomb Magnets

Abstract

Frustrated magnets with highly degenerate ground states are at the heart of hunting exotic states of matter. Recent studies in spin-orbit coupled honeycomb magnets have generated immense interest in bond-dependent interactions, appreciating a symmetric off-diagonal $\Gamma$ interaction which exhibits a macroscopic degeneracy in the classical limit. Here, we study a generic spin model and discover a novel chiral-spin ordering with spontaneously broken time-reversal symmetry near the dominant $\Gamma$ region. The chiral-spin phase is demonstrated to possess a staggered chirality relation in different sublattices, and it exhibits gapless excitations as revealed by the vanishing energy gap and the finite central charge on cylinders. Although there is a vestige of a tiny peak in the corner of the second Brillouin zone, the magnetic order is likely to vanish as the system size increases. Finally, we also attempt to gain insight into the possible topological signature of the chiral-spin phase by calculating the dynamic structure factor and the modular $\mathcal{S}$ matrix.

12+6 pages, 9+11 figures, 1+2 tables. Accepted by Physical Review Research

References in corpus (11)

• Mott Insulators in the Strong Spin-Orbit Coupling Limit: From Heisenberg to a Quantum Compass and Kitaev Models
• $\alpha$-RuCl3: a Spin-Orbit Assisted Mott Insulator on a Honeycomb Lattice
• An exact chiral spin liquid with non-Abelian anyons
• Order by disorder and spiral spin liquid in frustrated diamond lattice antiferromagnets
• Experimental identification of quantum spin liquids
• Hidden symmetries of the extended Kitaev-Heisenberg model: Implications for honeycomb lattice iridates A2IrO3
• Theory of the field-revealed Kitaev spin liquid
• Emergence of Chiral Spin Liquids via Quantum Melting of Non-Coplanar Magnetic Orders
• Order-by-disorder in the antiferromagnetic Ising model on an elastic triangular lattice
• Unveiling the phase diagram of a bond-alternating spin-$\frac{1}{2}$ $K$-$\Gamma$ chain
• Susceptibility anisotropy and its disorder evolution in models for Kitaev materials

Cited by in corpus (8)

• Beyond Kitaev physics in strong spin-orbit coupled magnets
• Easy-plane anisotropic-exchange magnets on a honeycomb lattice: quantum effects and dealing with them
• Effects of charge doping on Mott insulator with strong spin-orbit coupling, Ba${}_2$NaOsO${}_6$
• Interplay of magnetic field and trigonal distortion in the honeycomb $\Gamma$ model: Occurrence of a spin-flop phase
• Chiral spin state and nematic ferromagnet in the spin-1 Kitaev-$\Gamma$ model
• Successive topological phase transitions in two distinct spin-flop phases on the honeycomb lattice
• Interplay of Kitaev Interaction and Off-diagonal Exchanges: Exotic Phases and Quantum Phase Diagrams
• Continuous phase transition from a chiral spin state to collinear magnetic order in a zigzag chain with Kitaev interactions