文章基本信息

标题：Signature of a continuous quantum phase transition in non-equilibrium energy absorption: Footprints of criticality on higher excited states
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作者：Sirshendu Bhattacharyya ; Subinay Dasgupta ; Arnab Das 等
期刊名称：Scientific Reports
电子版ISSN：2045-2322
出版年度：2015
卷号：5
DOI：10.1038/srep16490
出版社：Springer Nature
摘要：Understanding phase transitions in quantum matters constitutes a significant part of present day condensed matter physics. Quantum phase transitions concern ground state properties of many-body systems, and hence their signatures are expected to be pronounced in low-energy states. Here we report signature of a quantum critical point manifested in strongly out-of-equilibrium states with finite energy density with respect to the ground state and extensive (subsystem) entanglement entropy, generated by an external pulse. These non-equilibrium states are evidently completely disordered (e.g., paramagnetic in case of a magnetic ordering transition). The pulse is applied by switching a coupling of the Hamiltonian from an initial value ( λ _I) to a final value ( λ _F) for sufficiently long time and back again. The signature appears as non-analyticities (kinks) in the energy absorbed by the system from the pulse as a function of λ _F at critical-points (i.e., at values of λ _F corresponding to static critical-points of the system). As one excites higher and higher eigenstates of the final Hamiltonian H ( λ _F) by increasing the pulse height , the non-analyticity grows stronger monotonically with it. This implies adding contributions from higher eigenstates help magnifying the non-analyticity, indicating strong imprint of the critical-point on them. Our findings are grounded on exact analytical results derived for Ising and XY chains in transverse field.