Pulse current response of high-T_c superconducting vortex flow transistors

The properties of superconducting vortex flow transistor (SVFT), which consist of a vortex flow channel and a control line for applying a magnetic field, are diagnosed by using a current pulses train method. The time-domain waveforms of the vortex flow voltage along the channel were measure using the current pulses train with the pulse width of 5 ms as input signals. The fast response of the flow voltage suggests that the heating effect is negligible and the effect of the magnetic field generated by the control line was dominant in our measurement. The vortex flow speed was estimated from the ratio of the flux flow voltage to the control current, and was found to be 8.6×10 ⁴ m/s. We also estimated the pinning energy E_p from the vortex flow speed, and found that the value of E_p is around 8.6 meV for our device, which can be easily excited by a conventional Ti:sapphire femtosecond laser.