Department of Physics, Lancaster University, Bailrigg, Lancaster LA1 4YB, UK.
VTT Technical Research Centre of Finland Ltd, P.O. Box 1000, 02044, VTT, Espoo, Finland.
Sci Rep. 2017 Apr 4;7:45566. doi: 10.1038/srep45566.
We demonstrate significant cooling of electrons in a nanostructure below 10 mK by demagnetisation of thin-film copper on a silicon chip. Our approach overcomes the typical bottleneck of weak electron-phonon scattering by coupling the electrons directly to a bath of refrigerated nuclei, rather than cooling via phonons in the host lattice. Consequently, weak electron-phonon scattering becomes an advant- age. It allows the electrons to be cooled for an experimentally useful period of time to temperatures colder than the dilution refrigerator platform, the incoming electrical connections, and the host lattice. There are efforts worldwide to reach sub-millikelvin electron temperatures in nanostructures to study coherent electronic phenomena and improve the operation of nanoelectronic devices. On-chip magnetic cooling is a promising approach to meet this challenge. The method can be used to reach low, local electron temperatures in other nanostructures, obviating the need to adapt traditional, large demagnetisation stages. We demonstrate the technique by applying it to a nanoelectronic primary thermometer that measures its internal electron temperature. Using an optimised demagnetisation process, we demonstrate cooling of the on-chip electrons from 9 mK to below 5 mK for over 1000 seconds.
我们通过在硅片上的薄膜铜的退磁，将电子在纳米结构中冷却到 10mK 以下，证明了这一点。我们的方法通过将电子直接与冷冻核浴耦合，而不是通过主晶格中的声子来冷却，克服了电子与声子弱散射的典型瓶颈。因此，弱电子-声子散射成为一个优势。它允许电子在实验上有用的时间内冷却到比稀释制冷器平台、输入的电子连接和主晶格更冷的温度。全球都在努力达到亚毫开尔文的电子温度，以研究相干电子现象和提高纳米电子器件的性能。在纳米结构中，基于磁体的冷却方法是实现这一目标的一种很有前途的方法。该方法可用于达到其他纳米结构中的低、局域电子温度，避免了适应传统的大型退磁阶段的需要。我们通过将其应用于一种测量内部电子温度的纳米电子初级温度计，来证明这一技术。通过优化的退磁过程，我们证明了在超过 1000 秒的时间内，电子从 9mK 冷却到 5mK 以下。
