[Seminar] Coupled Trimer Description of Kagome Compound Volborthite

Speaker

Dr. Tsutomu Momoi - RIKEN, Japan

Title

Coupled Trimer Description of Kagome Compound Volborthite

Abstract

Volborthite offers a stimulating example of a frustrated quantum magnet. It contains both ferromagnetic and antiferromagnetic interactions on anisotropic kagome layers. A density functional theory calculation has provided a magnetic model based on coupled trimers [1]. This model shows a broad 1/3-magnetization plateau, which is consistent with the experimentally observed plateau behavior. This model also presents a scenario for the appearance of a spin nematic phase below the 1/3 plateau phase. Recently, we study the effects of Dzyaloshinskii-Moriya (DM) interactions in volborthite [2], deriving an effective spin model of S=1/2 pseudospins on trimers. We show that, for a magnetic field perpendicular to the kagome layer, magnon excitations from the 1/3-plateau feel a Berry curvature due to the DM interactions, giving rise to a thermal Hall effect. A comparison with the experiment suggests that the one-dimensionality is stronger than the previous estimation of exchange couplings. Based on this picture, we further analyze low-temperature magnetic phase diagrams.

[1] O. Janson, S. Furukawa, T. Momoi, P. Sindzingre, J. Richter, and K. Held, Phys. Rev. Lett. 117, 037206 (2016).
[2] S. Furukawa and T. Momoi, J. Phys. Soc. Jpn. 89, 034711 (2020).

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