Speaker

Dr. Rico Pohle/ The University of Tokyo

Dr. Rico Pohle obtained his PhD from OIST under the supervision of Prof. N. Shannon and Dr. L. D. C. Jaubert for working on statistical mechanics, and semi-classical approaches to thermodynamic and dynamic properties in spin liquids. As a PostDoc, he joined the group of Prof. M. Imada in Tokyo to learn and apply quantum many body methods to frustrated magnets. Currently, He works in the group of Prof. Y. Motome on higher-spin Kitaev magnets.

Title

Spin nematic, dimensional reduction, and chiral spin liquid in the spin-1 Kitaev-Heisenberg model with biquadratic interactions

Abstract

The Kitaev model on the honeycomb lattice is an elegant realization of a quantum spin liquid, showing fractionalized excitations and topological order [1]. While it has been discussed mainly for materials with an effective spin-orbital entangled moment S=1/2 [2], theoretical studies suggest that the model could also be realized for S=1 or even larger S [3]. S=1 spin moments are special since they allow not only for dipolar but also quadrupolar fluctuations on a single site, while supporting higher-order biquadratic interactions. Such interactions can lead to unconventional states, as seen, e.g., in spin nematic phases [4]. 
  In this talk, I show that the Kitaev model under the influence of bilinear-biquadratic interactions hosts many unconventional ordered and disordered phases. By using a global energy optimization scheme in combination with classical Monte Carlo simulations in the spin space U(3) [5], we obtain a comprehensive phase diagram offering chiral ordered and quadrupolar ordered phases, in addition to already known ferro, antiferro, zigzag and stripy phases. Intriguingly, next to quadrupolar ordered and semi-ordered phases, we find that the competition between Kitaev and positive biquadratic interactions also promotes a noncoplanar finite-temperature spin liquid state, with macroscopic degeneracy and finite scalar chirality [6].

[1] A. Kitaev, Ann. Phys. 321, 2 (2006).
[2] G. Jackeli and G. Khaliullin, Phys. Rev. Letters 102, 017205 (2009).
[3] P. P. Stavropoulos, D. Pereira, and H.-Y. Kee, Phys. Rev. Letters 123, 037203 (2019).
[4] H. Tsunetsugu and M. Arikawa, J. Phys. Soc. Jpn. 75, 083701 (2006).
[5] K. Remund, R. Pohle, Y. Akagi, J. Romhányi, and N. Shannon Phys. Rev, Research 4, 033106 (2022).
[6] R. Pohle, N. Shannon, and Y. Motome, arXiv:2212.10040

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