Colloquium 139:

Title: Development of Surface-Sensitive Electrical Transport Measurement System and Its Application to Thinnest High-Tc Superconductor Film

Speaker: Canhua Liu, Department of Physics and Astronomy, Shanghai Jiao Tong University

Location: Room 111, Physics Building

Time: 15:00-16:30p, Wed, March 5, 2014

Abstract:

Existence of crystal surface and interface may reduce the spatial degrees of freedom of carriers, and thus results in various novel quantum phenomena related to the reduction of dimensionality. Measuring the electronic transport of a crystal surface and/or thin films thereon is very important not only to the potential application of materials but also to fundamental researches. It is highly desirable to obtain the electronic structure, morphology information and transport property of a material in situ, since they are strongly related. Based on a commercial apparatus equipped with scanning tunneling microscope (STM) and molecular beam epitaxy (MBE) system, we developed an surface-sensitive electronic transport measurement system that is compatible with the STM. A micro-four-point probe (MFPP) is utilized to increase the surface sensitivity in the transport measurement, which can be conducted at low temperature (Tmin=300 mK) and high magnetic field (Bmax=11 T). This new system was firstly used to measure FeSe thin film grown on SrTiO3(001) surface. The most exciting result is that we found its critical temperature (Tc) is as high as 109 K, which is much higher than Tc of any other iron-based superconductors found so far. This is also the first time to found a non-Cu-based superconductor with Tc higher than liquid-nitrogen temperature (77 K).