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In this seminar, we discuss two topics on the spin nematic order in quantum spin systems: (1) some hint to detect a spin-1 nematic order using a magnetic field and (2) finding a plethora of quadrupolar phases in a spin-1 dimer system. The spin nematic, or quadrupolar, order is an example of “hidden order”, and how to detect it in an actual material has been extensively discussed for years. A particularly important subject is to find a more realistic and experimentally-accessible system, since many of previously investigated models stabilizing the spin nematic order are either rather unrealistic or require a very high magnetic field. In the first topic, we discuss the magnetic field effect on the two-dimensional spin-1 bilinear-biquadratic model, a canonical model for spin-1 nematics, where we find a reentrant behavior in the finite-temperature transition to the ferro-nematic phase as a function of a magnetic field [1]. This reentrant behavior is an entropic effect that can be attributed to different robustness of the paramagnetic and ferro-nematic phases in a magnetic field. In the second topic, we discuss three types of the quadrupolar phases of triplet dimers in a two-dimensional spin-1 dimer system [2]. They can be classified in terms of internal degrees of freedom of a spin-1 dimer. In particular, we argue that one of the quadrupolar phases with the p-type vector chiral correlation may explain the spin-liquid-like behavior observed in the ruthenium dimer material Ba3ZnRu2O9 [3].
References:
[1] K. Tanaka and C. Hotta, Phys. Rev. B 102, 140401(R) (2020).
[2] K. Tanaka and C. Hotta, Phys. Rev. B 101, 094422 (2020).
[3] I. Terasaki et al., J. Phys. Soc. Jpn. 86, 033702 (2017).
I am a PhD candidate in Department of Basic Science, University of Tokyo (my defense is scheduled in January, 2021). Before my PhD course, I obtained my Bachelor degree in Department of Chemistry, University of Tokyo in 2016 and my Master degree in Department of Basic Science, University of Tokyo in 2018. My major is condensed matter theory, especially in the subject of the nematic/quadrupolar orderings in quantum spin systems. For solving corresponding many-body systems, I use numerical methods such as exact diagonalization and Monte Carlo methods.
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