Order from disorder:: Quantum spin gap in magnon spectra of LaTiO3 -: art. no. 212405

被引:40
作者
Khaliullin, G [1 ]
机构
[1] Max Planck Inst Festkorperforsch, D-70569 Stuttgart, Germany
关键词
D O I
10.1103/PhysRevLett.87.212405
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
A theory of the anisotropic superexchange and low-energy spin excitations in a Mott insulator with t(2 g) orbital degeneracy is presented. We observe that the spin-orbit coupling induces frustrating Ising-like anisotropy terms in the spin Hamiltonian, which invalidate noninteracting spin-wave theory. The frustration of classical states is resolved by an order from disorder mechanism, which selects a particular direction of the staggered moment and generates a quantum spin gap. The theory explains well the observed magnon gaps in LaTiO3. As a test case, a specific prediction is made on the splitting of magnon branches at certain momentum directions.
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页数:4
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