Determination of the density of states in high-T<Subscript>c</Subscript> thin films using FET-type microstructures

A simple electronic experiment using a field-effect-transistor–type microstructure is suggested. The thin superconductor layer forms the source-drain channel of a layered structure across which an AC current is applied. It is found necessary to measure the second harmonic of the source-gate voltage, and the third harmonic of the source-drain voltage; these electronic measurements then give the logarithmic derivative of the density of states, which is an important consideration when fitting parameters of the band structure. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2006