凝聚态物理前沿讲座_方忠_Quantum Simulation in the Field of Spintronics and Orbitronics.ppt

 Fully spin polarized anomalous Hall current in MnAs Spin conductivity AHE conductivity Anomalous Nernst Effect B V FM V Conventional Anomalous Inverse Anomalous Nernst Effect: Cooling and refrigerator FM Heat current jQ Ex Heat current: Eq. of motion: eg t2g 3z2-r2 x2-y2 xy yz zx Orbitronics Orbital Degrees of Freedom (ODF) Energy Down spin Up spin EF O-2p O-2p t2g t2g eg eg 2-fold (ODF) 3-fold “Half-metal” Various Orderings FM A-type C-type G-type Lattice Spin Charge Orbital SC, TMR, CMR, M-I Transition, Anomalous Hall Effect, Magneto-optical, Ferroelectricity, Piezoelectricity, etc … Experimental Theoretical SCIENCE 288, 462(2000). J. Phys. Soc. Jap. 68, 3790(1999). Phase Diagram of Tetragonal La1-xSrxMnO3 (Controlling of Orbital and Spin Orderings) Z. Fang K. Terakura, PRL 84, 3169(2000). FM A-AF C-AF G-AF Orbital and Spin Orderings Physics: Spin Orbital Lattice Double exchange Super-exchange Compression Less conductivity Electric-Field-induced Orbital Switching K. Hatsuda, APL 83, 3329 (2003). Lattice Spin Charge Orbital Electronic Structures of Ca2-xSrxRuO4 Energy Down spin Up spin EF O-2p O-2p t2g t2g eg eg 3-fold Ca2-xSrxRuO4 : Isovalent substitution Rotation Rotation Rotation + + Tilting Tilting + Compression AF Mott Insulator Nearly FM Metal S. Nakatsuji, et al., PRL O. Friedt, et al., PRB Issues: (1) How to understand the complicated phase diagram. (2) What’s the rule of orbital. Effects of Structure Distortions Z. Fang K. Terakura, PRB64, R20509(2001) Rotation xy orbital VHS FM Tilting yz, zx nesting AF * * * * * * * * 方 忠 中国科学院物理研究所，理论室 Quantum Simulation in the Field of Spintronics and Orbitronics Acknowledgement: Y. G. Yao, K. Terakura N. Nagaosa Y. Tokura 凝聚