Variational Study of the Two-Impurity Spin-Boson Model with a Common Ohmic Bath: Ground-State Phase Transitions
Variational Study of the Two-Impurity Spin-Boson Model with a Common Ohmic Bath: Ground-State Phase Transitions
复制标题
具有公共欧姆浴的二杂质自旋玻色子模型的变分研究：基态相变
DOI：
10.1002/andp.201800120
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发表时间：
2018
影响因子：
2.4
通讯作者：
Zhao Yang
中科院分区：
文献类型：
--
作者：
Zhou Nengji;Zhang Yuyu;Lü Zhiguo;Zhao Yang
利用试探波函数，对一个嵌入玻色子欧姆浴中的双杂质系统的基态量子相变进行了多D1阶广义变分计算，计算参数超过1万个.研究了杂质体系和欧姆玻色子浴中的量子临界性，精确地确定了相应的临界点和临界指数。利用欧姆谱密度的线性网格，本文的数值计算产生了比采用离散化因子远大于1的对数网格的其他计算更好的具有较低能量的基态的描述。这为文献中关于临界耦合的相当大的争议提供了一个可能的解决方案。此外，在强反铁磁自旋-自旋耦合的存在下，基态相变被推断为一阶相变，与铁磁体系或不存在自旋-自旋耦合的情况下的相变不同，其中该相变属于Kosterlitz-无自旋普适类。
By means of a trial wave function, the multi‐D1ansatz, extensive variational calculations with more than 10 000 parameters are carried out to study quantum phase transitions in the ground states of a two‐impurity system embedded in a common Ohmic bath of bosons. Quantum criticality in both the impurity system and the Ohmic bosonic bath is investigated with relevant transition points and critical exponents determined accurately. With the linear grid of the Ohmic spectral density, numerical calculations herein produce a much better description of the ground states with lower energies than other calculations employing a logarithmic grid with a discretization factor far greater than unity. This offers a possible resolution to the considerable controversy on the critical coupling in the literature. Moreover, the ground‐state phase transition is inferred to be of first order in the presence of strong antiferromagnetic spin–spin coupling, at variance with that in the ferromagnetic regime or in the absence of spin–spin coupling where the transition belongs to the Kosterlitz–Thouless universality class.