Versatile system for point contact conductance spectroscopy

Abstract

A versatile system has been designed and constructed which is being used for point contact and tunnelling studies. A cryostat capable of going down to 1.5 K is equipped with a differential screw mechanism and a piezoelectric tube which help to make the point contact junctions in liquid helium. An attractive feature of this cryostat is the movable multitip arrangement. This enables the construction and study of four different point contact junctions under the same conditions in a single experiment. A simple analogue circuit built with low cost integrated circuits and components is used to measure the differential conductance, dl/dV, directly. This system has been used for studying electron transport across metal-metal and normal metal-superconductor microcontacts. Point contact tunnelling measurements have also been carried out on high T_c oxide superconductors to determine the superconducting gap parameter, Δ.