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Quantum phase transitions in the spin-boson model without the counterrotating terms
- Source :
- Phys. Rev. B 100, 115106 (2019)
- Publication Year :
- 2018
-
Abstract
- We study the spin-boson model without the counterrotating terms by a numerically exact method based on variational matrix product states. Surprisingly, the second-order quantum phase transition (QPT) is observed for the sub-Ohmic bath in the rotating-wave approximations. Moreover, first-order QPTs can also appear before the critical points. With the decrease of the bath exponents, these first-order QPTs disappear successively, while the second-order QPT remains robust. The second-order QPT is further confirmed by multi-coherent-states variational studies, while the first-order QPT is corroborated with the exact diagonalization in the truncated Hilbert space. Extension to the Ohmic bath is also performed, and many first-order QPTs appear successively in a wide coupling regime, in contrast to previous findings. The previous pictures for many physical phenomena for the spin-boson model in the rotating-wave approximation have to be modified at least at the strong coupling.<br />Comment: 10 pages, 10 figures
- Subjects :
- Condensed Matter - Statistical Mechanics
Quantum Physics
Subjects
Details
- Database :
- arXiv
- Journal :
- Phys. Rev. B 100, 115106 (2019)
- Publication Type :
- Report
- Accession number :
- edsarx.1812.03758
- Document Type :
- Working Paper
- Full Text :
- https://doi.org/10.1103/PhysRevB.100.115106