Van Hove Excitons and High-T$_c$ Superconductivity: VIIIC Dynamic Jahn-Teller Effects vs Spin-Orbit Coupling in the LTO Phase of La$_{2-x}$Sr$_x$CuO$_4$

R. S. Markiewicz

doi:10.1016/0921-4534(93)90029-P

paper

Van Hove Excitons and High-T $_{c}$ Superconductivity: VIIIC Dynamic Jahn-Teller Effects vs Spin-Orbit Coupling in the LTO Phase of La $_{2 - x}$ Sr $_{x}$ CuO $_{4}$

arXiv:cond-mat/9303020 · doi:10.1016/0921-4534(93)90029-P

Abstract

The possible role of the van Hove singularity (vHs) in stabilizing the low-temperature orthorhombic (LTO) phase transition in La $_{2 - x}$ \-Sr $_{x}$ \-CuO $_{4}$ (LSCO) is discussed. It is found that the vHs can drive a structural distortion in two different ways, either due to spin-orbit coupling or to dynamic Jahn-Teller (JT) effects. This paper discusses the latter effect in some detail. It is shown that a model Hamiltonian introduced earlier to describe the coupled electron -- octahedral tilt motions (`cageons') has a series of phase transitions, from a high-temperature disordered JT phase (similar to the high-temperature tetragonal phase of LSCO) to an intermediate temperature dynamic JT phase, of average orthorhombic symmetry (the LTO phase) to a low temperature static JT phase (the low temperature tetragonal phase). For some parameter values, the static JT phase is absent.

28 pages plain TeX, 14 figures available upon request, NU-MARKIEWIC-93-01

Van Hove Excitons and High-Tc​ Superconductivity: VIIIC Dynamic Jahn-Teller Effects vs Spin-Orbit Coupling in the LTO Phase of La2−x​Srx​CuO4​

Abstract

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Van Hove Excitons and High-T $_{c}$ Superconductivity: VIIIC Dynamic Jahn-Teller Effects vs Spin-Orbit Coupling in the LTO Phase of La $_{2 - x}$ Sr $_{x}$ CuO $_{4}$