Topological excitations in frustrated lattices

Datum

08.05.2015

Zeit

14:00 - 15:00

Sprecher

Xuefeng Zhang

Zugehörigkeit

University of Kaiserslautern

Sprache

en

Hauptthema

Physik

Andere Themen

Physik

Host

CMT seminars

Beschreibung

Topological excitations ( such as fractional charges and strings ) are reminiscent of the particle physics, but we now also found them in frustrated many body system. In the first part of this talk[1], we analyze the repulsive hard core bosons in the optical Kagome lattice with cylindrical boundary condition. By using quantum Monte Carlo simulations and an effective single string excitation model, we found that fractional charges can be excited in this system. Depending on their chiralities, they exist on different edges to form an edge liquid phase. Meanwhile, the strings between them fluctuate in the bulk which will destroys the stripe order. In the second part, we investigate the XXZ model on the triangular lattice with anisotropic ferromagnetic xy coupling and antiferromagnetic z coupling. In previous work[2], an incommensurate supersolid phase was found when introducing anisotropy of interactions in different directions. However, the mechanism of the incommensurate phase is still unknown. In the strong coupling region, we found that quantum fluctuation of domain wall excitations can reduce the energy and cause the incommensurate order. By using quantum Monte Carlo simulations, we confirmed our theoretical analysis and found that the number of domain walls and the incommensurate k-vector monotonically increase with the anisotropy. [1] X.-F. Zhang and S. Eggert, Phys. Rev. Lett. 111, 147201 (2013) [2] S. V. Isakov, et al. EPL, 87 36002 (2009)

Letztmalig verändert: 08.05.2015, 09:42:11