The maximal speed v of magnetic flux quanta is determined by the time of electron energy relaxation and is thus essential for superconducting microstrip single-photon detectors (SMSPDs). However, the deduction of v from the current-voltage (I-V) curves is hindered by the unknown number of vortices, as a small number of fast-moving vortices can induce the same voltage as a large number of slow-moving ones. At certain conditions, the I-V curve of a superconducting constriction exhibit kinks when the number of fluxons crossing the constriction is increased by one. By a deliberate injenction of fluxons into a supercondutor, we explore single- and few-fluxon regimes in the vortex dynamics and deduce the relaxation times of unpaired electrons whose knowledge is critical for the SMSPDs.
Project Staff: Dr. Zahra Makhdoumi Kakhaki, Ekaterina Pribytova
Major publications: