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記
日時：２０１９年１１月２０日（水）１３時３０分〜 Wed, Nov 20, 1:30pm
場所：東京大学 生産技術研究所 千葉実験所 研究実験棟Ｉn210号室
道程：http://hatano-lab.iis.u-tokyo.ac.jp/access-j.html (English: hatano-lab.iis.u-tokyo.ac.jp/access-e.html)
講師：Hyun-Yong Lee さん (東大物性研) Dr. Hyun-Yong Lee (ISSP, U. Tokyo)
演題：Gapless Kitaev Spin Liquid to Loop and String Gases through Tensor Networks
要旨：Kitaev honeycomb model (KHM) is one of the rare examples of the exactly solvable quantum many-body model [1]. It hosts two distinct phases, the Z2 topologically ordered phase, which is adiabatically connected to the toric code state, and the gapless Kitaev spin liquid (KSL) phase exhibiting the low energy Majorana excitations [1]. In particular, the fact that the KSL phase can be driven into the non-Abelian topological phase by breaking the time-reversal symmetry attracts lots of interests in experimental and theoretical studies. In this talk, we try to understand the KSL from a new perspective, i.e., the loop gas (LG) and string gas (SG) states which are efficiently and compactly defined in the tensor network representation [2]. One can show in a local tensor level that the LG and SG states, which we propose, not only respect the symmetries of KSL but also satisfy the vortex-free condition [2]. Also, those are critical states characterized by 2D Ising CFT and hav
e the Z2 gauge redundancy which allows us to create and move the vortex excitations exactly. Furthermore, accurate variational energy for the KHM is obtained with only two variational parameters [2], which ensures that our ansatze represent quantitatively as well as qualitatively the KSL. We discuss their physical properties, relation to classical statistical mechanics and topological properties in details.
参考文献
[1] A. Kitaev, Annals of Physics 321(2006) 2-111.
[2] H. Y. Lee, R. Kaneko, T. Okubo, and N. Kawashima, arXiv:1901.05786.
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李 宰河
〒277-8574 千葉県柏市柏の葉5-1-5
東京大学生産技術研究所
e-mail: lee@iis.u-tokyo.ac.jp
Tel: 04-7136-6977
Fax: 04-7136-6978
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