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arXiv · 1410.4067

Ground state properties of sub-Ohmic spin-boson model with simultaneous diagonal and off-diagonal coupling

Nengji Zhou·Lipeng Chen·Yang Zhao·Dima Mozyrsky·Vladimir Chernyak
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Abstract

By employing the variational approach, density matrix renormalization group (DMRG), exact diagonalization as well as symmetry and mean-field analyses, the ground state properties of the two-bath spin boson model with simultaneous diagonal and off-diagonal coupling are systematically studied in the sub-Ohmic regime. A novel quantum phase transition from a doubly degenerate "localized phase" to the other doubly degenerate "delocalized phase" is uncovered. Via the multi-D1 ansatz as the variational wave function, transition points are determined accurately, consistent with the results from DMRG and exact diagonalization. An effective spatial dimension $d_{eff} = 2.37(6)$ is then estimated, which is found to be compatible with the mean-field prediction. Furthermore, the quantum phase transition is inferred to be of first order for the baths described by a continuous spectral density function. In the case of single mode, however, the transition is softened.

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Nengji Zhou, Lipeng Chen, Yang Zhao, Dima Mozyrsky, Vladimir Chernyak. 2014-10-15. Ground state properties of sub-Ohmic spin-boson model with simultaneous diagonal and off-diagonal coupling. https://doi.org/10.1103/physrevb.90.155135

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