NbTiN纳米带中的声子heat capacity和自加热正常畴
Phonon heat capacity and self-heating normal domains in NbTiN nanostrips
摘要：
通过测量不同衬底温度下的稳态电流-电压滞回特性，表征了NbTiN纳米超导薄带中的自加热正常畴。温度的依赖性和电流的大小，这维持在不同的电压平衡域，只能解释与声子热容量明显小于预期的3-D德拜声子。这种减少的热容量与早些时候从相同薄膜的磁导和光响应研究中获得的值相吻合。从温度为Te的电子到温度为TB的衬底中的声子的热流速率与（T_e^p - T_B^p）成比例，指数p~3，这不同于由电子-声子相互作用或通过膜/衬底界面的3-d德拜声子逃逸介导的热流的指数。我们把这两个发现的平均晶粒尺寸的薄颗粒状NbTiN薄膜的声子谱的效果。我们的研究结果对于理解利用薄颗粒膜的超导器件中的热输运具有重要意义。
英文摘要：
Self-heating normal domains in thin superconducting NbTiN nanostrips were characterized via steady-state hysteretic current-voltage characteristics measured at different substrate temperatures. The temperature dependence and the magnitude of the current, which sustains a domain in equilibrium at different voltages, can only be explained with a phonon heat capacity noticeably less than expected for 3-d Debye phonons. This reduced heat capacity coincides with the value obtained earlier from magnetoconductance and photoresponse studies of the same films. The rate of heat flow from electrons at a temperature Te to phonons in the substrate at a temperature TB is proportional to (T_e^p - T_B^p) with the exponent p~3, which differs from the exponents for heat flows mediated by the electron-phonon interaction or by escaping of 3-d Debye phonons via the film/substrate interface. We attribute both findings to the effect of the mean grain size on the phonon spectrum of thin granular NbTiN films. Our findings are significant for understanding the thermal transport in superconducting devices exploiting thin granular films.
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