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TT: Fachverband Tiefe Temperaturen

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

TT 49.3: Talk

Wednesday, March 20, 2024, 15:30–15:45, H 2053

Finite-size effects in Heisenberg-Kitaev models — •Wilhelm Krüger and Lukas Janssen — Institute for Theoretical Physics, TU Dresden, 01062 Dresden

The Heisenberg-Kitaev model is a paradigmatic model to describe the magnetism in honeycomb-lattice Mott insulators with strong spin-orbit coupling, such as A₂IrO₃ (A = Na, Li), α-RuCl₃, and Na₂Co₂TeO₆. Due to the sign problem in quantum Monte Carlo simulations, the model can be studied numerically exactly only on small lattices. Here, we investigate in detail the finite-size effects, by carefully comparing numerical exact diagonalization calculations with semi-analytical nonlinear spin-wave theory. This allows us to establish a protocol to obtain improved estimates for various observables from finite-size extrapolations to the thermodynamic limit, including the spectral gap, the local magnetization, and phase transition points.

Keywords: Heisenberg-Kitaev model; finite-size effects; exact diagonalization; spin-wave theory