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タイトル: Majorana quantization and half-integer thermal quantum Hall effect in a Kitaev spin liquid
著者: Kasahara, Y.
Ohnishi, T.
Mizukami, Y.
Tanaka, O.
Ma, Sixiao
Sugii, K.
Kurita, N.
Tanaka, H.
Nasu, J.
Motome, Y.
Shibauchi, T.
Matsuda, Y.
著者名の別形: 笠原, 裕一
大西, 隆史
水上, 雄太
馬, 斯嘯
杉井, かおり
栗田, 伸之
田中, 秀数
那須, 譲治
求, 幸年
芝内, 孝禎
松田, 祐司
キーワード: Magnetic properties and materials
Quantum Hall
Topological matter
発行日: 11-Jul-2018
出版者: Springer Nature
誌名: Nature
巻: 559
号: 7713
開始ページ: 227
終了ページ: 231
抄録: The quantum Hall effect in two-dimensional electron gases involves the flow of topologically protected dissipationless charge currents along the edges of a sample. Integer or fractional electrical conductance is associated with edge currents of electrons or quasiparticles with fractional charges, respectively. It has been predicted that quantum Hall phenomena can also be created by edge currents with a fundamentally different origin: the fractionalization of quantum spins. However, such quantization has not yet been observed. Here we report the observation of this type of quantization of the Hall effect in an insulating two-dimensional quantum magnet1, α-RuCl3, with a dominant Kitaev interaction (a bond-dependent Ising-type interaction) on a two-dimensional honeycomb lattice. We find that the application of a magnetic field parallel to the sample destroys long-range magnetic order, leading to a field-induced quantum-spin-liquid ground state with substantial entanglement of local spins. In the low-temperature regime of this state, the two-dimensional thermal Hall conductance reaches a quantum plateau as a function of the applied magnetic field and has a quantization value that is exactly half of the two-dimensional thermal Hall conductance of the integer quantum Hall effect. This half-integer quantization of the thermal Hall conductance in a bulk material is a signature of topologically protected chiral edge currents of charge-neutral Majorana fermions (particles that are their own antiparticles), which have half the degrees of freedom of conventional fermions. These results demonstrate the fractionalization of spins into itinerant Majorana fermions and Z2 fluxes, which is predicted to occur in Kitaev quantum spin liquids1, 3. Above a critical magnetic field, the quantization disappears and the thermal Hall conductance goes to zero rapidly, indicating a topological quantum phase transition between the states with and without chiral Majorana edge modes. Emergent Majorana fermions in a quantum magnet are expected to have a great impact on strongly correlated quantum matter, opening up the possibility of topological quantum computing at relatively high temperatures.
記述: 幻の粒子「マヨラナ粒子」の発見 --トポロジカル量子コンピューターの実現に期待--. 京都大学プレスリリース. 2018-07-12.
著作権等: This is the accepted manuscript of the article, which has been published in final form at https://doi.org/10.1038/s41586-018-0274-0.
The full-text file will be made open to the public on 11 January 2019 in accordance with publisher's 'Terms and Conditions for Self-Archiving'.
This is not the published version. Please cite only the published version. この論文は出版社版でありません。引用の際には出版社版をご確認ご利用ください。
URI: http://hdl.handle.net/2433/233602
DOI(出版社版): 10.1038/s41586-018-0274-0
PubMed ID: 29995863
関連リンク: http://www.kyoto-u.ac.jp/ja/research/research_results/2018/180712_1.html
出現コレクション:学術雑誌掲載論文等

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