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arXiv:cond-mat/0607209 · Physical Review B

Phase diagram of the spin-Peierls chain with local coupling: Density-matrix renormalization-group calculations and unitary transformations

Alexander Weiße, Georg Hager, A. R. Bishop, Holger Fehske

Published Dec 27, 2006• 16 citations
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Abstract

We explore the ground-state phase diagram of a Heisenberg spin chain coupled locally to optical phonons (bond coupling), using large-scale density-matrix renormalization-group calculations and extending a unitary transformation approach which removes the spin-phonon coupling in leading order. For the quantum phase transition from the spin liquid to the dimerized phase, we find deviations from previous quantum Monte Carlo and flow equation results.

DOI
10.1103/physrevb.74.214426

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We explore the ground-state phase diagram of a Heisenberg spin chain coupled locally to optical phonons (bond coupling), using large-scale density-matrix renormalization-group calculations and extending a unitary transformation approach which removes the spin-phonon coupling in leading order. For the quantum phase transition from the spin liquid to the dimerized phase, we find deviations from previous quantum Monte Carlo and flow equation results.
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Recently, it has been proposed that higher-spin analogs of the Kitaev interactions K>0K>0K>0 may also occur in a number of materials with strong Hund's and spin-orbit coupling. In this work, we use Lanczos diagonalization and density matrix renormalization group methods to investigate numerically the S=1S=1S=1 Kitaev-Heisenberg model. The ground-state phase diagram and quantum phase transitions are investigated by employing local and nonlocal spin correlations. We identify two ordered phases at negative Heisenberg coupling J<0J<0J<0: a ferromagnetic phase with $\ensuremath{\langle}{S}_{i}^{z}{S}_{i+1}^{z}\ensuremath{\rangle}>0$ and an intermediate left-left-right-right phase with $\ensuremath{\langle}{S}_{i}^{x}{S}_{i+1}^{x}\ensuremath{\rangle}\ensuremath{\ne}0$. A quantum spin liquid is stable near the Kitaev limit, while a topological Haldane phase is found for J>0J>0J>0.