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arXiv 2208.01409cond-mat.quant-gascond-mat.str-el
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玻色-哈伯德模型中超过Gutzwiller近似的量子涨落

Quantum fluctuations beyond the Gutzwiller approximation in the Bose-Hubbard model

Fabio Caleffi

摘要:

从玻色-哈伯德(BH)模型的最先进的知识和最近的方法发展的费米子对应的启发,这项工作涉及的集体动力学的格子玻色气体超越平均场图片通过量子描述其基本激发的研究。在Gutzwiller方法中,通过BH作用的Bogoliubov二次化进行的哈密顿量子化,允许将理论的有效作用扩展到平均场解周围波动的二阶,以及预示识别集体模式的主要衰减顶点和其他在二阶水平上不明显的效应的可能性。这种量子描述扩展了标准的Bogoliubov方法的超流玻色系统的研究,包括更高的激发分支,包括希格斯模式在超流相,并确定其物理意义与适当的观测值,可以考虑到他们的实验表征。量子化过程的最终目的是确定基本量,如凝析油的损耗和有效超流部分,这是无法通过平均场描述或不完全表征的强相互作用的制度。

英文摘要:

Taking inspiration from the state-of-the art knowledge of the Bose-Hubbard (BH) model and recent methodological developments in its fermionic counterpart, this work deals with the study of the collective dynamics of a lattice Bose gas beyond the mean-field picture through a quantum description of its elementary excitations. The Hamiltonian quantization, performed via a Bogoliubov quadratization of the BH action within the Gutzwiller approach, allows to expand the effective action of the theory up to second order in the fluctuations around the mean-field solution, as well as to prefigure the possibility of identifying the main decay vertices of the collective modes and other effects that are not evident at the second-order level. This quantum description extends the standard Bogoliubov approach to the study of superfluid Bose systems for comprising higher excitation branches, including the Higgs mode in the superfluid phase, and identifies their physical meaning together with appropriate observables which could be taken into consideration for their experimental characterization. The ultimate aim of the quantization procedure is the determination of fundamental quantities as the depletion of the condensate and the effective superfluid fraction, which are not accessible by a mean-field description or not completely characterized in the regime of strong interactions.

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