Posazhennikova Anna, Trujillo-Martinez Mauricio, Kroha Johann
Department of Physics, Royal Holloway, University of London, Egham, Surrey TW20 0EX, United Kingdom.
Physikalisches Institut and Bethe Center for Theoretical Physics, Universität Bonn, Nussallee 12, D-53115 Bonn, Germany.
Phys Rev Lett. 2016 Jun 3;116(22):225304. doi: 10.1103/PhysRevLett.116.225304. Epub 2016 Jun 2.
A Bose gas in a double-well potential, exhibiting a true Bose-Einstein condensate (BEC) amplitude and initially performing Josephson oscillations, is a prototype of an isolated, nonequilibrium many-body system. We investigate the quasiparticle (QP) creation and thermalization dynamics of this system by solving the time-dependent Keldysh-Bogoliubov equations. We find avalanchelike QP creation due to a parametric resonance between BEC and QP oscillations, followed by slow, exponential relaxation to a thermal state at an elevated temperature, controlled by the initial excitation energy of the oscillating BEC above its ground state. The crossover between the two regimes occurs because of an effective decoupling of the QP and BEC oscillations. This dynamics is analogous to elementary particle creation in models of the early universe. The thermalization in our setup occurs because the BEC acts as a grand canonical reservoir for the quasiparticle system.
处于双势阱中的玻色气体，展现出真正的玻色 - 爱因斯坦凝聚（BEC）振幅且最初进行约瑟夫森振荡，是一个孤立的、非平衡多体系统的原型。我们通过求解含时的凯尔迪什 - 博戈留波夫方程来研究该系统的准粒子（QP）产生和热化动力学。我们发现，由于BEC与QP振荡之间的参量共振，会出现雪崩式的QP产生，随后是缓慢的指数弛豫，弛豫到一个温度升高的热态，该热态由振荡的BEC高于其基态的初始激发能控制。这两种状态之间的转变是由于QP和BEC振荡的有效解耦。这种动力学类似于早期宇宙模型中的基本粒子产生。我们所设置系统中的热化现象之所以发生，是因为BEC为准粒子系统充当了巨正则系综。
