曲率将声子霍尔粘度转化为声子角动量
Curvature Converts Phonon Hall Viscosity into Phonon Angular Momentum
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中文总结 AI 辅助
研究了平坦晶体膜中声子霍尔粘度相关问题，发现静态曲率可打开霍尔活性弯曲通道，通过无迹曲率与平均曲率作用产生面内声子角动量，还可据此估计扭矩，为探测原子级薄晶体中声子霍尔粘度提供了方法。
中文摘要 AI 辅助
在平坦的晶体膜中，低能谱由不与声子霍尔粘度耦合的弯曲模式主导。我们表明，静态曲率将法向运动转化为面内应变，从而打开一个霍尔活性弯曲通道。无迹曲率直接耦合到霍尔活性剪切，而平均曲率通过普通面内弹性产生的剪切间接起作用。这些通道共同沿表面法线产生面内声子角动量。对于统计各向同性的浅波纹，时间平均值具有由霍尔粘度确定的确定符号，产生与均方曲率成比例的稳定场奇扭矩。使用测量的α-RuCl₃的体霍尔粘度来设定尺度，我们估计几层膜的扭矩约为10⁻²² N·m，在已证明的扭转传感器的范围内。相同的弯曲到剪切响应提供了对原子级薄晶体中声子霍尔粘度的探测。
英文摘要
In a flat crystalline membrane, the low-energy spectrum is dominated by a flexural mode that does not couple to phonon Hall viscosity. We show that static curvature converts normal motion into in-plane strain and thereby opens a Hall-active flexural channel. Tracefree curvature couples directly to Hall-active shear, while mean curvature acts indirectly through the shear generated by ordinary in-plane elasticity. Together, these channels generate in-plane phonon angular momentum along the surface normal. For statistically isotropic shallow ripples, the time average has a definite sign fixed by the Hall viscosity, producing a steady field-odd torque proportional to the mean-square curvature. Using the measured bulk Hall viscosity of $α$-RuCl$_3$ to set the scale, we estimate a torque of order $10^{-22}\,\mathrm{N\,m}$ for a few-layer membrane, within reach of demonstrated torsional sensors. The same flexural-to-shear response provides a probe of phonon Hall viscosity in atomically thin crystals.
