KCrF3中的轨道有序及其成因

强关联体系中的轨道有序及其成因一直是凝聚态物理研究的热点问题.轨道有序对于巨磁阻和 超导材料的研究有非常重要的地位.利用第一性原理计算研究了KCrF₃的四方相和立方相中的轨道有序 及其成因.在四方相中, GGA和GGA+U两种方法计算结果都表明其基态是A型反铁磁和G型轨道有序. 对于立方结构, GGA方法得出铁磁半金属态是基态,而GGA+U(U_eff = 3.0 eV)得到的基态是A型 反铁磁绝缘体. 光电导测量是少数能从实验上观察到轨道有序的方法之一,因此计算了其光电导,并结合投影态密度讨论 了KCrF₃中的轨道有序.最后找到了其轨道有序的成因:电子强关联效应,而非电-声子相互作用是其 轨道 有序的物理根源.

Orbital ordering and its origin of KCrF3

The electronic, the magnetic and the orbital structures of KCrF₃ are studied by first principles in its recently identified crystallographic phases (tetragonal and cubic) [Margadonna and Karotsis 2006 J. Am. Chem. Soc. 128 16436]. In tetragonal phase, both generalized gradient approximation (GGA) and GGA+U calculations show that the ground state is the A-type antiferromagnetic (A-AFM) configuration with G-type orbital ordering pattern. Our calculations show that the orbital structures and the magnetic configurations can be measured by the optical conductivity. In the cubic state, the GGA calculations show that the ground state is ferromagnetic half metal state, while the GGA+U(U_eff = 3.0 eV) calculations show that the A-AFM insulator phase is the ground state. Our calculations indicate that the electron-electron interactions rather than the electron-phonon interactions are the driving forces behind the orbital order.