Quantum phase transitions in the spin-boson model without the counterrotating terms
| Autor: | Wang, Yan-Zhi, He, Shu, Duan, Liwei, Chen, Qing-Hu |
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| Rok vydání: | 2018 |
| Předmět: | |
| Zdroj: | Phys. Rev. B 100, 115106 (2019) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1103/PhysRevB.100.115106 |
| Popis: | 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. Comment: 10 pages, 10 figures |
| Databáze: | arXiv |
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