Photoresponse mechanism of superconducting magnesium diboride

The recent discovery of superconductivity in MgB2, with its BCS-like Cooper pairing mechanism and the 40-K critical temperature, and the demonstration of efficient single-optical-photon detection in superconducting NbN nanowire meanders inspired an interest in the development of superconducting radiation detectors based on MgB2.; We report the results of our experimental and theoretical studies of a photoresponse mechanism in superconducting MgB2 thin films and microbridges. We demonstrate that despite the two-gap nature of this material, the nonequilibrium superconducting recovery dynamics in MgB2 is similar to conventional one-gap, both low- and high-temperature superconductors and is governed by quasiparticle recombination, limited by the phonon bottleneck mechanism.; Our measured 100-ps-wide responses in MgB2 superconducting microbridges, operated at temperatures above 20 K, make this material promising for superconducting photodetector applications.