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물리학과 특별세미나 개최 안내
페이스북으로 보내기 트위터로 보내기 구글플러스로 보내기

1. 연사: 지성대 박사 (MPK)
2. 일시: 2018. 4. 2(월), 오후 2시
3. 장소: 공학3동 201호 (세미나실)
4. 제목: Kitaev Quantum Spin Liquid and Its Beyond


  The Kitaev quantum spin liquid (QSL) model has fascinated condensed matter physicists for a decade because they are exactly solvable, provide a variety of QSL phases, and are relevant for transition metal compounds such as irridates and ruthenates. This model implements the exchange frustration by bond-dependent Ising-like spin interaction on the ideal two-dimensional honeycomb lattice resulting in an exactly solvable topological QSL ground state and fractional spin excitations represented by noble Majorana fermions. In the past decade, experimental realization of the Kitaev QSL model and direct observation of Majorana quasiparticles have been eagerly pursued and now it becomes challenging to explore exotic quantum phases due to additional perturbative spin interactions appearing in real materials.
    In this talk, I will present the experimental evidences of Majorana fermions in a layered van der Waals compound α-RuCl3. Neutron and x-ray diffraction measurements reveal that the low-temperature crystal structure forms a perfect Ru-honeycomb lattice, which provides an ideal platform for the Kitaev honeycomb quantum spin lattice.[1] Extensive neutron spectroscopic and thermodynamic measurements directly demonstrated Majorana fermionic excitations as a result of thermal fractionalization of Jeff = ½ pseudospins, which is well reproduced by numerical simulations obtained from the Kitaev model.[2] Furthermore, I will present recent progress in pursuit of exotic quantum phases and critical behaviors invoked by an external magnetic field or pressure on this material.[3]

[1] S.-Y. Park et al., arXiv:1609.05690v1.
[2] S.-H. Do et al., Nature Physics 13, 1079 (2017).
[3] S. Ji et al., in preparation