arXiv:1711.08882 · Physical Review A
Dynamics of a quantum phase transition in the Bose-Hubbard model: Kibble-Zurek mechanism and beyond
Keita Shimizu, Yoshihito Kuno, Takahiro Hirano, Ikuo Ichinose
Abstract
In this paper, we study the dynamics of the Bose-Hubbard model by using time-dependent Gutzwiller methods. In particular, we vary the parameters in the Hamiltonian as a function of time, and investigate the temporal behavior of the system from the Mott insulator to the superfluid (SF) crossing a second-order phase transition. We first solve a time-dependent Schr\"odinger equation for the experimental setup recently done by Braun et al. [Proc. Natl. Acad. Sci. USA 112, 3641 (2015)] and show that the numerical and experimental results are in fairly good agreement. However, these results disagree with the Kibble-Zurek scaling. From our numerical study, we reveal a possible source of the discrepancy. Next, we calculate the critical exponents of the correlation length and vortex density in addition to the SF order parameter for a Kibble-Zurek protocol. We show that beside the ``freeze'' time $\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{t}$, there exists another important time, ${t}_{\mathrm{eq}}$, at which an oscillating behavior of the SF amplitude starts. From calculations of the exponents of the correlation length and vortex density with respect to a quench time ${\ensuremath{\tau}}_{\mathrm{Q}}$, we obtain a physical picture of a coarsening process. Finally, we study how the system evolves after the quench. We give a global picture of dynamics of the Bose-Hubbard model.