Khaliullin G, Maekawa S
Max-Planck-Institut fur Festkorperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany and Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
Phys Rev Lett. 2000 Oct 30;85(18):3950-3. doi: 10.1103/PhysRevLett.85.3950.
We present a theory of spin and orbital states in Mott insulator LaTiO3. The spin-orbital superexchange interaction between d(1)(t(2g)) ions in cubic crystal suffers from a pathological degeneracy of orbital states at the classical level. Quantum effects remove this degeneracy and result in the formation of the coherent ground state, in which the orbital moment of t(2g) level is fully quenched. We find a finite gap for orbital excitations. Such a disordered state of local degrees of freedom on unfrustrated, simple cubic lattice is highly unusual. Orbital liquid state naturally explains observed anomalies of LaTiO3.
我们提出了一种关于莫特绝缘体LaTiO₃中自旋和轨道态的理论。立方晶体中d(¹)(t₂g)离子之间的自旋 - 轨道超交换相互作用在经典水平上存在轨道态的病态简并。量子效应消除了这种简并，并导致形成相干基态，其中t₂g能级的轨道矩被完全淬灭。我们发现轨道激发存在有限能隙。在无挫折的简单立方晶格上这种局部自由度的无序状态非常不寻常。轨道液态自然地解释了LaTiO₃中观察到的异常现象。
