Polanco Carlos A, van Roekeghem Ambroise, Brisuda Boris, Saminadayar Laurent, Bourgeois Olivier, Mingo Natalio
Université Grenoble Alpes, CEA, LITEN, 17 rue des Martyrs, Grenoble, France.
Université Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, Grenoble, France.
Sci Adv. 2023 Oct 13;9(41):eadi7439. doi: 10.1126/sciadv.adi7439.
The thermal conductance quantum is a fundamental quantity in quantum transport theory. However, two decades after its first reported measurements and calculations for phonons in suspended nanostructures, reconciling experiments and theory remains elusive. Our massively parallel calculations of phonon transport in micrometer-sized three-dimensional structures suggest that part of the disagreement between theory and experiment stems from the inadequacy of macroscopic concepts to analyze the data. The computed local temperature distribution in the wave ballistic nonequilibrium regime shows that the spatial placement and dimensions of thermometers, heaters, and supporting microbeams in the suspended structures can noticeably affect the thermal conductance's measured values. In addition, diffusive transport assumptions made in the data analysis may result in measured values that considerably differ from the actual thermal conductance of the structure. These results urge for experimental validation of the suitability of diffusive transport assumptions in measuring devices operating at sub-kelvin temperatures.
热导量子是量子输运理论中的一个基本量。然而，在首次报道对悬浮纳米结构中的声子进行测量和计算二十年后，使实验与理论相协调仍然难以实现。我们对微米级三维结构中的声子输运进行的大规模并行计算表明，理论与实验之间的部分分歧源于宏观概念在分析数据时的不足。在波动弹道非平衡状态下计算得到的局部温度分布表明，悬浮结构中温度计、加热器和支撑微梁的空间位置及尺寸会显著影响热导的测量值。此外，数据分析中所做的扩散输运假设可能导致测量值与结构的实际热导有很大差异。这些结果促使人们对在亚开尔文温度下运行的测量设备中扩散输运假设的适用性进行实验验证。
