Reifenberger Andreas, Reiser Andreas, Kempf Sebastian, Fleischmann Andreas, Enss Christian
Kirchhoff Institute for Physics, Heidelberg University, Im Neuenheimer Feld 227, 69120 Heidelberg, Germany.
Rev Sci Instrum. 2020 Mar 1;91(3):035118. doi: 10.1063/1.5139090.
We have developed a new micro-fabricated platform for the measurement of the specific heat of low heat capacity mg-sized metallic samples, such as superconductors, down to temperatures of as low as 10 mK. It addresses challenging aspects of setups of this kind such as the thermal contact between the sample and platform, the thermometer resolution, and an addenda heat capacity exceeding that of the samples of interest (typically nJ/K at 20 mK). The setup allows us to use the relaxation method, where the thermal relaxation following a well defined heat pulse is monitored to extract the specific heat. The sample platform (5 × 5 mm) includes a micro-structured paramagnetic Ag:Er temperature sensor, which is read out by a dc-superconducting quantum interference device via a superconducting flux transformer. In this way, a relative temperature precision of 30 nK/Hz can be reached, while the addenda heat capacity falls well below 0.5 nJ/K for T < 300 mK. A gold-coated mounting area (4.4 × 3 mm) is included to improve the thermal contact between the sample and platform.
我们开发了一种新型微加工平台，用于测量低热容毫克级金属样品（如超导体）的比热，测量温度低至10 mK。该平台解决了此类装置面临的诸多挑战性问题，例如样品与平台之间的热接触、温度计分辨率以及附加热容超过感兴趣样品的热容（在20 mK时通常为nJ/K）。该装置使我们能够采用弛豫法，即监测在明确的热脉冲之后的热弛豫过程来提取比热。样品平台（5×5毫米）包括一个微结构化顺磁Ag:Er温度传感器，该传感器由一个直流超导量子干涉装置通过一个超导磁通变压器进行读出。通过这种方式，可实现30 nK/Hz的相对温度精度，而对于T < 300 mK，附加热容远低于0.5 nJ/K。平台还设有一个镀金安装区域（4.4×3毫米），以改善样品与平台之间的热接触。
