Intertwined superfluid and density wave order in two-dimensional 4He
Intertwined superfluid and density wave order in two-dimensional 4He
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DOI：
10.1038/nphys4023
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发表时间：
2017-02
期刊：
影响因子：
19.6
通讯作者：
J. Nyéki;A. Phillis;A. Ho;Derek Lee;P. Coleman;J. Parpia;B. Cowan;J. Saunders
中科院分区：
文献类型：
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作者：
J. Nyéki;A. Phillis;A. Ho;Derek Lee;P. Coleman;J. Parpia;B. Cowan;J. Saunders
超流动性是量子力学定律在宏观尺度上运行的一种表现。在量子液体（液态氦是典型的例子）和超冷原子气体中，超流动性变得明显的条件已经得到了广泛的实验探索，包括作为维度的函数。特别令人感兴趣的是迄今为止尚未解决的固体是否可以是超流体的问题。在这里，我们报告了在受三角晶格势约束的二维玻色子系统中具有交织超流体和密度波序的量子物质的新状态的识别。利用扭转振荡器，我们测量了吸附在石墨表面的氦原子第二层在低至2 mK的宽温度范围内的超流体响应。超流动性是在一个狭窄的薄膜密度范围内观察到的，它突然出现，随后向量子临界点坍缩。超流体密度在零温度极限下的异常温度依赖性以及没有明确的超流体起始温度，通过反映密度波序的激发谱的ansatz和破坏规范对称和平移对称的准凝聚波函数，得到了自洽的解释。
Superfluidity is a manifestation of the operation of the laws of quantum mechanics on a macroscopic scale. The conditions under which superfluidity becomes manifest have been extensively explored experimentally in both quantum liquids (liquid4He being the canonical example) and ultracold atomic gases,, including as a function of dimensionality,. Of particular interest is the hitherto unresolved question of whether a solid can be superfluid,. Here we report the identification of a new state of quantum matter with intertwined superfluid and density wave order in a system of two-dimensional bosons subject to a triangular lattice potential. Using a torsional oscillator we have measured the superfluid response of the second atomic layer of4He adsorbed on the surface of graphite, over a wide temperature range down to 2 mK. Superfluidity is observed over a narrow range of film densities, emerging suddenly and subsequently collapsing towards a quantum critical point. The unusual temperature dependence of the superfluid density in the limit of zero temperature and the absence of a clear superfluid onset temperature are explained, self-consistently, by an ansatz for the excitation spectrum, reflecting density wave order, and a quasi-condensate wavefunction breaking both gauge and translational symmetry.