Full gap closing is a prerequisite for hosting Majorana zero modes in Josephson junctions on the surface of topological insulators.Previously,we have observed direct experimental evidence of gap closing in Josephson junctions constructed on Bi2Te3 surface.In this paper we report further investigations on the position dependence of gap closing as a function of magnetic flux in single Josephson junctions constructed on Bi2Te3 surface.
The Institute of Physics, Chinese Academy of Sciences, is in charge of the construction of the Synergetic Extreme Condition User Facility (SECUF) in Huairou, Beijing. The SECUF is a comprehensive facility focused on providing extreme physical conditions for scientific research, including an ultralow temperature, ultrahigh pressure, ultrahigh magnetic field, and ultrafast laser. The ultralow temperature will be realized by the sub-millikelvin (sub-mK) station, whose main component is an adiabatic nuclear demagnetization refrigerator (ANDR). The refrigerator is designed to have a base temperature below 1 mK and a magnetic field up to 16 T for experiments, as well as a characteristic parameter of B/T ≥-104 T/K. In this review, we introduce adiabatic nuclear demagnetization refrigeration, thermometry from 10 mK to sub-mK, the properties and parameters of the ANDR of the SECUF, and related prospective research topics.
Recently,a contact-resistance-measurement method was developed to detect the minigap,hence the Andreev bound states(ABSs),in Josephson junctions constructed on the surface of three-dimensional topological insulators(3D TIs).In this work,we further generalize that method to the circumstance with radio frequency(rf)irradiation.We find that with the increase of the rf power,the measured minigap becomes broadened and extends to higher energies in a way similar to the rf power dependence of the outer border of the Shapiro step region.We show that the corresponding data of contact resistance under rf irradiation can be well interpreted by using the resistively shunted Josephson junction(RSJ)model and the Blonder–Tinkham–Klapwijk(BTK)theory.Our findings could be useful when using the contact-resistancemeasurement method to study the Majorana-related physics in topological insulator-based Josephson junctions under rf irradiation.