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東京大学物性研究所
多田靖啓
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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 (Department of Physics and Astronomy, University of
Utah)
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.
URL
http://www.issp.u-tokyo.ac.jp/maincontents/seminar/all2.html?pid=3210&ptype=seminar