Schwab K, Henriksen EA, Worlock JM, Roukes ML
Condensed Matter Physics, California Institute of Technology, Pasadena 91125, USA.
Nature. 2000 Apr 27;404(6781):974-7. doi: 10.1038/35010065.
The physics of mesoscopic electronic systems has been explored for more than 15 years. Mesoscopic phenomena in transport processes occur when the wavelength or the coherence length of the carriers becomes comparable to, or larger than, the sample dimensions. One striking result in this domain is the quantization of electrical conduction, observed in a quasi-one-dimensional constriction formed between reservoirs of two-dimensional electron gas. The conductance of this system is determined by the number of participating quantum states or 'channels' within the constriction; in the ideal case, each spin-degenerate channel contributes a quantized unit of 2e(2)/h to the electrical conductance. It has been speculated that similar behaviour should be observable for thermal transport in mesoscopic phonon systems. But experiments attempted in this regime have so far yielded inconclusive results. Here we report the observation of a quantized limiting value for the thermal conductance, Gth, in suspended insulating nanostructures at very low temperatures. The behaviour we observe is consistent with predictions for phonon transport in a ballistic, one-dimensional channel: at low temperatures, Gth approaches a maximum value of g0 = pi2kB2T/3h, the universal quantum of thermal conductance.
介观电子系统的物理学已经被探索了超过15年。当载流子的波长或相干长度变得与样品尺寸相当或大于样品尺寸时，传输过程中就会出现介观现象。该领域一个引人注目的结果是在二维电子气储库之间形成的准一维缩颈中观察到的电导量子化。这个系统的电导由缩颈内参与的量子态或“通道”数量决定；在理想情况下，每个自旋简并通道对电导贡献一个量子化单位2e(2)/h。据推测，在介观声子系统中的热传输也应该能观察到类似行为。但到目前为止，在这个领域进行的实验结果尚无定论。在此，我们报告在极低温下悬浮绝缘纳米结构中热导Gth的量子化极限值的观测结果。我们观察到的行为与弹道一维通道中声子传输的预测一致：在低温下，Gth接近热导的通用量子g0 = π2kB2T/3h的最大值。
