强关联玻色液体中的热退相干
Thermal decoherence in a strongly correlated Bose liquid
摘要：
我们计算单粒子光谱函数的玻色液体的晶格上，在整数填充，接近超流莫特过渡。我们使用一个“静态路径近似”，保留所有的经典热波动的问题，和一个真正的空间实现的随机相位近似（RPA）的热波动背景上的格林函数。这导致在基态下的标准RPA答案，但捕获随着温度增加的激励的渐进阻尼。我们重点研究了超流到玻色液体热转变的动量分辨线形。在超流制度，我们观察到一个有间隙的“振幅”模式，和无间隙的“相位”模式的正能量和负能量。这些模式的色散和重量的变化与相互作用，但几乎是温度无关的，甚至进入正常状态，除了近临界耦合。模式的阻尼大致按$T^α f_{\bf k}$变化，其中$T$是温度，${\bf k}$是动量，$α\sim 0.5$和$f_{\bf k}$具有非平凡的动量依赖性。Mott相具有带隙的色散谱。在临界耦合附近，热玻色“液体”是有间隙的，随着温度的升高，间隙逐渐变宽，这是它与莫特绝缘体共有的特征。
英文摘要：
We compute the single particle spectral function of a Bose liquid on a lattice, at integer filling, close to the superfluid-Mott transition. We use a `static path approximation' that retains all the classical thermal fluctuations in the problem, and a real space implementation of the random phase approximation (RPA) for the Green's functions on the thermally fluctuating backgrounds. This leads to the standard RPA answers in the ground state but captures the progressive damping of the excitations with increasing temperature. We focus on the momentum resolved lineshape across the superfluid to Bose liquid thermal transition. In the superfluid regime we observe a gapped `amplitude' mode, and gapless `phase' modes of positive and negative energy. The dispersion and weight of these modes changes with interaction but are almost temperature independent, even into the normal state, except near critical coupling. The damping of the modes varies roughly as $T^α f_{\bf k}$, where $T$ is the temperature and ${\bf k}$ the momentum, with $α\sim 0.5$ and $f_{\bf k}$ having non trivial momentum dependence. The Mott phase has gapped dispersive spectra. Near critical coupling the thermal Bose `liquid' is gapped, with progressive widening of the gap with increasing temperature, a feature that it shares with the Mott insulator.
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