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Khoa Vật lý trân trọng kính mời quý vị đến dự seminar tháng 03/2019

Ngày: 29/03/2019 (Thứ 6)

Giờ: từ 10 giờ 00 sáng đến 11 giờ 00 sáng

Địa điểm: Phòng 408F, nhà T1, Đại học Khoa học Tự nhiên334Nguyễn Trãi


Speaker: Dr. DAO XUAN VIET (Advanced Institute for Science and Technology, Hanoi University of Science and Technology)


(Liên quan tới nghiên cứu được giải thưởng (giải nhất) công bố khoa học của viện AIST năm 2018) 

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].

References: [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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