Unlike the electrical conductance that can be widely modulated within the same material even in deep-subwavelength devices, tuning the thermal conductance within a single material system or nanostructure is extremely challenging and requires a large-scale device. This prohibits the realization of robust on/off states in switching the flow of thermal currents. Here, we present the theory of a thermal switch based on resonant coupling of three photonic resonators, in analogy to the field-effect electronic transistor composed of a source, a gate, and a drain. As a material platform, we capitalize on the extreme tunability and low-loss resonances observed in the dielectric function of monolayer hexagonal boron nitride ($h$-BN) under controlled strain. We derive the dielectric function of $h$-BN from first principles, including the phonon-polariton line widths computed by considering phonon-isotope and anharmonic phonon-phonon scattering. Subsequently, we propose a strain-controlled $h$-BN–based thermal switch that modulates the thermal conductance by more than an order of magnitude, corresponding to a contrast ratio in the thermal conductance of $98\mathrm{\%}$, in a deep-subwavelength nanostructure.

中文翻译：

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单层六方氮化硼中通过共振耦合的深亚波长热开关

与即使在深亚波长设备中也可以在同一材料内广泛调节的电导率不同，在单个材料系统或纳米结构内调整热导率极具挑战性，需要大型设备。这阻止了在切换热电流流中实现鲁棒的开/关状态。在这里，我们提出一种基于三个光子谐振器的谐振耦合的热开关理论，类似于由源极，栅极和漏极组成的场效应电子晶体管。作为材料平台，我们利用在单层六方氮化硼的介电功能中观察到的极端可调性和低损耗共振（$H$-BN）。我们推导了$H$-BN来自第一个原理，包括通过考虑声子-同位素和非谐声子-声子散射而计算出的声子-极化子线宽。随后，我们提出了应变控制$H$-基于BN的热敏开关，可将热导率调制一个数量级以上，对应于热导率中的对比度 $98\mathrm{％}$在深亚波长纳米结构中。