A Theory of Quantum Spin Nematics in a Quantum Magnet

Abstract

[evdate 2012-12-18] IAS Symposium on Frontiers in Condensed Matter Physics. Talk no. 10 Title from title slide.

Abstract: Quantum spin nematic (QSN) phase is a novel quantum phase of matter in magnets, which can be regarded as a quantum-spin analogue of nematic liquid crystal phase. The phase possesses neither any orderings of spin moment, nor crystalline solid-like structure in spin degrees of freedom. But, unlike spin-rotational symmetric quantum spin liquids (QSL), it exhibits an ordering of rank-2 traceless tensor spin operators, which are composed of two distinct spin operators defined on spatially different sites. Ground-state spin wavefunctions of QSN are essentially given by quantum-mechanical superpositions of a number of spatial partitionings of spin-triplet valence bonds and/or spin-singlet valence bonds, sharing similar features as those of QSL. Based on this observation, the speaker describe these ground-state wavefunctions in terms of spin-triplet variants of Anderson's resonating valence bond (RVB) state, so as to explore their possible realization in a certain realisti! c quantum frustrated model. We argue that dynamical spin structure factor in a QSN phase exhibit characteristic features at low-temperature regime, such as 'gauge-field' like collective modes with a finite spectral weight and continuum spectrum associated with gapped spinon band. Due to the Raman process associated with gapless director (spin) waves, the NMR relaxation rate in the same low-temperature (T) regime exhibits T^{2d-1} behavior where d is the effective spatial dimension.

Duration: 27 min.