Faculty of Physics, Hanoi University of Science

English (United Kingdom)

Seminar: Phase Transition Phenomena in 2D Generalized XY Model

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Bộ môn Tin Vật lý thuộc Khoa Vật lý, trường Đại học Khoa học Tự nhiên Hà Nội trân trọng kính mời quý vị đến dự seminar tháng 3/2019 do Khoa Vật lý tài trợ
Seminar sẽ được tổ chức theo lịch như sau:
Ngày: 29/03/2019 (Thứ 6)
Giờ: từ 10 giờ 00 sáng đến 11 giờ 00 sáng
Địa điểm: Phòng 408F, nhà T1, 334 Nguyễn Trãi
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Speaker: Dr. DAO XUAN VIET (Advanced Institute for Science and Technology, Hanoi University of Science and Technology)

Title: PHASE TRANSITION PHENOMENA IN 2D GENERALIZED XY MODEL

Abstract: In 1972, Kosterlitz and Thouless identified a new type of phase transition in two-dimensional systems where topological defects play a crucial role [1]. Particularly in the XY model, vortices and antivortices, which are topological excitations, lead to a phase transition from the disordered phase of free vortices at high temperatures to a low-temperature phase of quasi-long-range order of pairs of bound vortices. Several generalizations of the 2D XY model have been proposed in order to search for novel phenomena phase transition. Since 1985, starting with the works of Korshunov, Lee and Grinstein, the generalized XY models which include nematic interaction, give rise to further, fractional vortex excitations such as half-vortices. The emergence of both excitations leads to a richer phase diagram (disordered, nematic, quasi-long-range order phases) than for the standard XY model [2]. Recently, the generalized XY have seen renewed interest focusing in the behavior of the tricritical region where the paramagnetic, nematic, and quasi-long-range phases meet [3]. Our work shows signatures for the intermediate region starting from the tricritical point, where the transition line is neither of the same physics as the Ising transition below nor the Berezinskii-Kosterlitz-Thouless transition far above the tricritical point [4].

Refs:

[1] J M Kosterlitz and D J Thouless. Journal of Physics C: Solid State Physics 6(7), 1181 (1973) (Nobel prize 2016).

[2] S. E. Korshunov, JETP Lett. 41, 263 (1985); D. H. Lee and G. Grinstein, Phys. Rev. Lett. 55, 541 (1985).

[3] Y. Shi, A. Lamacraft, and P. Fendley, Phys. Rev. Lett. 107, 240601 (2011).

[4] Duong Xuan Nui et al, Phys. Rev. B 98, 144421 (2018).

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Trân trọng,
Bộ môn Tin Vật lý.
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