Quantum phase transition in the delocalized regime of the spin-boson model
Quantum phase transition in the delocalized regime of the spin-boson model
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DOI：
10.1103/physrevb.84.174301
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发表时间：
2011-06
影响因子：
3.7
通讯作者：
Qing-Jun Tong;J. An;Hong-Gang Luo;C. Oh
中科院分区：
文献类型：
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作者：
Qing-Jun Tong;J. An;Hong-Gang Luo;C. Oh
欧姆自旋-玻色子模型中离域-局域量子相变(QPT)的存在已被公认。虽然定域区的物理相对简单，但非定域区却表现出许多有趣的行为。这里我们揭示了在这种状态下存在着一种新的QPT：即从一个没有束束态的相到一个有束束态的相，这导致了这两个相中完全不同的动力学行为。如果库最初处于位移真空态(即相干态)，则当束缚态存在时，自旋动力学呈现无损耗振荡，否则，振荡将完全衰变。这一结果与发生在小隧道极限内的相干-非相干相变是一致的。我们的工作表明，自旋-玻色子模型中的QPT物理还需要进一步的探索。
The existence of the delocalized-localized quantum phase transition (QPT) in the ohmic spin-boson model has been commonly recognized. While the physics in the localized regime is relatively simple, the delocalized regime shows many interesting behaviors. Here we reveal that in this regime there exists a novel QPT: namely, from a phase without a bound state to a phase with a bound state, which leads to completely different dynamical behaviors in these two phases. If the reservoir is initially in the displaced vacuum state (i.e., the coherent state), the spin dynamics exhibits lossless oscillation when the bound state exists; otherwise, the oscillation will decay completely. This result is compatible with the coherence-incoherence transition occurring in the small-tunneling limit. Our work indicates that the QPT physics in the spin-boson model needs further exploration.