Critical Dynamics of Singlet Excitations in a Frustrated Spin System

Дата и время публикации : 2000-01-19T21:34:49Z

Авторы публикации и институты :
Valeri N. Kotov (University of Florida)
Michael E. Zhitomirsky (ETH, Zurich)
Oleg P. Sushkov (ETH, Zurich)

Ссылка на журнал-издание: Phys. Rev. B 63, 064412 (2001).
Коментарии к cтатье: 5 pages, 5 figures, additional discussion and figure added, to appear in Phys. Rev. B
Первичная категория: cond-mat.str-el

Все категории : cond-mat.str-el

Краткий обзор статьи: We construct and analyze a two-dimensional frustrated quantum spin model with plaquette order, in which the low-energy dynamics is controlled by spin singlets. At a critical value of frustration the singlet spectrum becomes gapless, indicating a quantum transition to a phase with dimer order. This T=0 transition belongs to the 3D Ising universality class, while at finite temperature a 2D Ising critical line separates the plaquette and dimerized phases. The magnetic susceptibility has an activated form throughout the phase diagram, whereas the specific heat exhibits a rich structure and a power law dependence on temperature at the quantum critical point. We argue that the novel quantum critical behavior associated with singlet criticality discussed in this work can be relevant to a wide class of quantum spin systems, such as antiferromagnets on Kagome and pyrochlore lattices, where the low-energy excitations are known to be spin singlets, as well as to the CAVO lattice and several recently discovered strongly frustrated square-lattice antiferromagnets.

Category: Physics