ISSP - The institute for Solid State Physics

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Chiral liquid phase of simple quantum magnets
日程 : 2017年11月20日(月) 13:30 - 14:30 場所 : 物性研究所本館6階 第2セミナー室 (A612) 講師 : Prof. Oleg Starykh 所属 : Department of Physics and Astronomy, University of Utah 世話人 : 押川正毅 (63275)

We study a T = 0 quantum phase transition between a quantum paramagnetic state and a magnetically ordered state for a spin S = 1 XXZ Heisenberg antiferromagnet on a two-dimensional triangular lattice. The transition is induced by an easy plane single-ion anisotropy D. At the mean¬field level, the system undergoes a direct transition at a critical D = Dc between a paramagnetic state at D > Dc and an ordered state with broken U(1) symmetry at D < Dc. We show that beyond mean-field the phase diagram is very different and includes an intermediate chiral liquid phase. Specifically, we find that the Ising (Jz) component of the Heisenberg exchange creates an attraction between magnons in the paramagnetic phase and binds magnons into a two-particle bound state. This two-magnon bound state condenses at D > Dc, pre-emptying single particle condensation, and gives rise to a chiral liquid phase which spontaneously breaks spatial inversion symmetry, but leaves the spin-rotational and time-reversal symmetries intact. The chiral liquid phase is characterized by a finite vector chirality without long range dipolar magnetic order. We corroborate our analytic treatment with a numerical analysis and show evidence of the chiral phase by means of the density matrix renormalization group calculations.

(公開日: 2017年11月15日)