Speaker

Prof. Masafumi Udagawa
Gakushuin University, Tokyo

Title

Local detection of Majorana zero mode in Kitaev’s chiral spin liquid

Abstract

Kitaev's spin liquid is drawing considerable attention as a realistic stage of the quantum spin liquid phase. Among its fascinating properties, the field-induced chiral spin liquid (CSL) state deserves special attention, where the half-integer quantization of thermal Hall conductivity is theoretically predicted, and is experimentally reported for one of the candidate materials, alpha-RuCl3 [1]. The appearance of Majorana zero mode (MZM) is another remarkable phenomenon expected in the CSL phase. A fractional excitation called vison accompanies MZM and behaves as a non-Abelian Ising anyon. The existence of MZM implies a strange non-locality of the CSL state, where one quantum bit is fractionalized, and associated quantum information can be stored nonlocally. It has been long awaited to realize topological quantum computation based on this MZM. However, for its realization, it is crucial to enable the detection and control of the MZM on a real-space basis[2,3].
In this talk, towards the real-space control of MZM, we address the response of Kitaev's spin liquid state to the local perturbations.
To this aim, we focus on the CSL phase of Kitaev's model and construct a low-energy effective theory of vison motion.
In particular, on the basis of the effective theory, we point out that visons can be localized by applying a strong local magnetic field.
We consider this idea in an experimental setup of the scanning tunneling microscopy, and discuss the possibility of trapping visons [4].

[1] Y. Kasahara et al., Nature 559, 227 (2018).
[2] M. Udagawa, S. Takayoshi and T. Oka, Phys. Rev. Lett. 126, 127201 (2021).
[3] M. O. Takahashi, M. G. Yamada, M. Udagawa, T. Mizushima and S. Fujimoto, arXiv:2211.13884.
[4] M. Udagawa, S. Takayoshi and T. Oka, in preparation.

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