Damping of the Higgs and Nambu-Goldstone modes of superfluid Bose gases at finite temperatures
Damping of the Higgs and Nambu-Goldstone modes of superfluid Bose gases at finite temperatures
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DOI：
10.1093/ptep/ptw061
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发表时间：
2016-03
期刊：
影响因子：
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通讯作者：
Kazuma Nagao;I. Danshita
中科院分区：
文献类型：
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作者：
Kazuma Nagao;I. Danshita
我们研究了光学晶格中相应填充的超流体玻色气体的集体模式。我们关注莫特绝缘体的量子相变附近，除了与自发 U(1) 对称破缺相关的南部-戈德斯通相模式之外，还存在希格斯振幅模式。我们使用有效的 spin-1 模型和基于有限温度格林函数的场论方法来分析有限温度对集体模式阻尼的影响。我们计算高达 1 环阶的阻尼率，并对其进行分析和数值评估。我们表明，希格斯模式的阻尼率随着温度的升高而增加，但在实验中达到的典型温度下它仍然保持欠阻尼。此外，我们发现 Nambu-Goldstone 模式通过与 Higgs 模式相互作用产生的朗道阻尼过程而衰减，并且在特定参数区域的典型温度下可能会出现过阻尼。
We study collective modes of superfluid Bose gases in optical lattices at commensurate fillings. We focus on the vicinity of the quantum phase transition to the Mott insulator, where there exists the Higgs amplitude mode in addition to the Nambu-Goldstone phase mode associated with the spontaneous U(1) symmetry breaking. We analyze finite-temperature effects on the damping of the collective modes by using an effective spin-1 model and the field theoretical methods based on the finite-temperature Green's function. We calculate the damping rates up to 1-loop order and evaluate them analytically and numerically. We show that the damping rate of the Higgs mode increases with increasing the temperature but it remains underdamped up to a typical temperature achieved in experiments. Moreover, we find that the Nambu-Goldstone mode attenuates via a Landau damping process resulting from interactions with the Higgs mode and it can be overdamped at the typical temperature in a certain parameter region.