Cryogen-free dilution refrigerator system with selected options

我们建议购买一个适合于SQUID磁力计的无低温稀释冰箱，以研究在毫开尔文温度下的磁化特性。虽然工作温度低至1.5K的Squid无处不在，但在较低温度下工作的系统在现场却没有。然而，关于拓扑绝缘体的磁性和超导特性，有一些重要的问题需要这样的仪器来解决。例如，考虑构成新的SI单位制基础的电量子效应。磁性拓扑绝缘体是一种很有前途的新材料，它可以在没有磁场的情况下以量子反常霍尔效应（QAHE）的形式实现量子霍尔电阻器。然而，这些拓扑绝缘体中的铁磁状态的性质仍然不清楚。为了理解这种状态，必须在样品显示QAHE的相同条件下进行测量，目前QAHE远低于1K。因此，主要目标是开发技术来准确表征QAHE器件的磁性和结构特性，特别是使用SQUID传感器的高分辨率v掺杂（Bi,Sb）Te系统，可以在从30K到10mK的可变温度下工作，这将使我们能够回答有关该材料铁磁状态性质的一些基本物理问题。除了这一主要目的之外，mK-SQUID的可用性将有利于拓扑超导项目和我们对磁性ti的其他研究。该仪器将在该领域提供独特的功能，并将使我们能够显着推进对这些重要新材料的理解。

We propose to purchase a cryogen-free dilution refrigerator appropriate for the incorporation of a SQUID magnetometer, for the purpose of studying magnetization properties at millikelvin temperatures. While Squid operating down to about 1.5K are omnipresent, systems working at lower temperatures are absent in the field. There are however significant questions, with regards to magnetic and superconducting properties of Topological insulators which require precisely such an instrument to address. For example, consider the electrical quantum effects that form the basis of the new SI unit system. A promising new material class for applications in this field are the magnetic topological insulators, which allows the quantum Hall resistors to be realized without a magnetic field, in the form of the quantum anomalous Hall effect (QAHE). However, the nature of the ferromagnetic state in these topological insulators is still unclear. To understand this state, it must be measured under the same conditions where the samples exhibit the QAHE, which at present is well below 1K. A major objective is thus to develop techniques to accurately characterize the magnetic and structural properties of the QAHE devices, especially V-doped (Bi,Sb)Te system with high resolution using the SQUID sensor that can work in variable temperatures from 30K down to 10mK, which will allow us to answer some fundamental physics questions on the nature of the ferromagnetic state in this material. In addition to this primary aim, the availability of mK-SQUID will be beneficial to projects on topological superconductivity and to our other investigation on magnetic TIs in general. This instrument will provide a unique functionality in this field, and will allow us to significantly move forward the understanding of these important novel materials.