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TT: Fachverband Tiefe Temperaturen

TT 49: Frustrated Magnets: Strong Spin-Orbit Coupling I

TT 49.6: Talk

Wednesday, March 20, 2024, 16:15–16:30, H 2053

Spin vestigial orders in extended Heisenberg-Kitaev models near hidden SU(2) points: Application to Na₂Co₂TeO₆ — •Niccolò Francini and Lukas Janssen — Technische Universität Dresden, Dresden, Germany

The honeycomb magnet Na₂Co₂TeO₆ has recently been argued to realize an approximate hidden SU(2) symmetry that can be understood by means of a duality transformation. Using classical Monte Carlo simulations, we study the finite-temperature phase diagram of the Heisenberg-Kitaev-Γ-Γ′ model near the hidden-SU(2)-symmetric point, in the presence of a six-spin ring exchange perturbation. At low temperatures, the model features collinear single-q zigzag and noncollinear triple-q ground states, depending on the sign of the ring exchange coupling. In the vicinity of the hidden-SU(2)-symmetric point, the magnetic long-range orders melt in two stages. The two phases at intermediate temperatures spontaneously break spin rotational and lattice translational symmetries, respectively, leaving time reversal symmetry intact, and are understood as vestigial orders of the underlying magnetic states. We identify these vestigial orders as Z₃ spin nematic and Z₄ spin current density wave phases. The latter is a candidate for the paramagnetic 2D long-range-ordered state observed in Na₂Co₂TeO₆.

Keywords: Kitaev materials; Kitaev-Heisenberg model; Duality transformation; Classical Monte-Carlo simulation; Cobaltates