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[QuantumMaterialSeminar]
Chiral liquid phase of simple quantum magnets
Date : Monday, November 20th, 2017 13:30 - 14:30 Place : Seminar Room 2 (A612), 6th Floor, ISSP Lecturer : Prof. Oleg Starykh Affiliation : Department of Physics and Astronomy, University of Utah Committee Chair : Masaki Oshikawa (63275)
e-mail: oshikawa@issp.u-tokyo.ac.jp

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.


(Published on: Wednesday November 15th, 2017)