Electron-electron and electron-phonon interactions in highly correlated quasi-one-dimensional transition metal compounds
In this dissertation, we study the one-dimensional (1-D) Peierls-Hubbard (PH) Hamiltonian in the strong-coupling regime (large-to-infinite-Hubbard-U) with application to the following two quasi-one-dimensional transition metal compounds: Vanadium dioxide (VO{sub 2}) and the halogen-bridge transition metal linear chain complexes (the MX materials). We focus our study on the effects of electron-electron and electron-phonon correlations in the various competing symmetry-breaking phase in the ground state, as well as the topological excitation corresponding to local defect states of the system which determine the optical and transport properties, and doping behavior of the system. In Chapter 2, we propose an intermediate-to-strong-coupling, spin-Peierls theory for VO{sub 2} in it low-temperature phase, and find a spectrum of low-lying magnetic excitations corresponding to local defect states in the multi-photon spectrum. In Chapters 3 and 4, we study the 1-D, two-band PH model at 3/4-filling in the large-U limit with applications to certain MX materials. In the charge-degrees of freedom, both the continuum theory as well as discreteness effects of the lattice are examined. In addition to obtaining irrationally charged soliton-antisoliton (S{bar S}) pairs in the continuum theory, a massive, localized polaron is found which is missing from the continuum limit. In the spin-degrees of freedom, we study ground-state magnetic ordering as well as the low-lying magnetic excitation spectrum. Two types of charge-transfer instabilities of the system are also discussed.
- Research Organization:
- Univ. of California, Los Angeles, CA (United States)
- OSTI ID:
- 114805
- Resource Relation:
- Other Information: TH: Thesis (Ph.D.); PBD: 1992
- Country of Publication:
- United States
- Language:
- English
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