School of Physical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India.
School of Chemical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India.
Phys Rev E. 2023 Mar;107(3-1):034141. doi: 10.1103/PhysRevE.107.034141.
We analyze the phase diffusion, quantum fluctuations and their spectral features of a one-dimensional Bose-Josephson junction (BJJ) nonlinearly coupled to a bosonic heat bath. The phase diffusion is considered by taking into account of random modulations of the BJJ modes causing a phase loss of initial coherence between the ground and excited states, whereby the frequency modulation is incorporated in the system-reservoir Hamiltonian by an interaction term linear in bath operators but nonlinear in system (BJJ) operators. We examine the dependence of the phase diffusion coefficient on the on-site interaction and temperature in the zero- and π-phase modes and demonstrate its phase transition-like behavior between the Josephson oscillation and the macroscopic quantum self-trapping (MQST) regimes in the π-phase mode. Based on the thermal canonical Wigner distribution, which is the equilibrium solution of the associated quantum Langevin equation for phase, coherence factor is calculated to study phase diffusion for the zero- and π-phase modes. We investigate the quantum fluctuations of the relative phase and population imbalance in terms of fluctuation spectra which capture an interesting shift in Josephson frequency induced by frequency fluctuation due to nonlinear system-reservoir coupling, as well as the on-site interaction-induced splitting in the weak dissipative regime.
我们分析了一维玻色-约瑟夫森结（BJJ）与玻色热浴非线性耦合的相位扩散、量子涨落及其谱特征。通过考虑 BJJ 模式的随机调制，考虑了相位扩散，这会导致基态和激发态之间初始相干性的相位损失，其中频率调制通过与浴算子线性但与系统（BJJ）算子非线性的相互作用项包含在系统-储库哈密顿量中。我们研究了相位扩散系数对零相和π相模式中局域相互作用和温度的依赖性，并在π相模式中展示了约瑟夫森振荡和宏观量子自捕获（MQST）区域之间的类似相变行为。基于热正则威格纳分布，这是关联量子朗之万方程的平衡解，用于计算零相和π相模式的相位扩散的相干因子。我们研究了相对相位和粒子数失衡的量子涨落，其波动谱捕捉到由于非线性系统-储库耦合引起的频率波动引起的约瑟夫森频率的有趣变化，以及在弱耗散区域中局域相互作用引起的分裂。
