Sirshendu Bhattacharyya, Arnab Das, Subinay Dasgupta
We study real-time dynamics of a quantum Ising chain driven by periodic instantaneous quenches of transverse field (the transverse field varying with time like a periodic rectangular wave symmetric about zero). Two interesting phenomena are reported and analysed: (A) We observe dynamical many-body freezing (Phys. Rev. B, vol. 82, 172402, 2010), i.e. strong quantum mechanical freezing of the response, with the degree of freezing depending non-monotonically on the driving parameters (pulse height and width). The freezing occurs due to suppression of dynamics of the many-body modes arising out of the interactions between the spins. For certain combination of the pulse height and period, maximal freezing (freezing peaks) are observed. For those parameter values, the response remains frozen very strongly close to its initial state for all time. (B) Emergence of a distinct solitary oscillation with frequency much lower than the driving frequency is observed. This slow oscillation dominates the response remarkably in the limit of long observation time. This is surprising because such dominance of a single oscillation occurs even when the driving is fast and strong (compared to the interaction energy scale), involving excitation of essentially many high energy modes. We identify this slow oscillation as the unique survivor of destructive quantum interference between the many-body modes. The oscillation is found to decay algebraically with time to a constant value. All the key features are demonstrated analytically, with numerical evaluations for specific results.
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http://arxiv.org/abs/1112.6171
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