Self-induced Shapiro effect in semiconductor superlattices

Summary form only given. In the last decades, a number of macroscopic quantum effects in solids have been investigated. Among those are the Josephson effect in weakly coupled superconductors and Bloch oscillations in semiconductor superlattices (SLs). The key effect of both phenomena is the generation of an AC effect by the application of a DC electric field to the system. For Bloch oscillations (BO), the periodic motion is due to Bragg reflection of electrons in a periodic potential when a constant bias field is applied across the structure. Josephson effect and Bloch oscillations show interesting extensions when both DC and AC voltages are applied. The current across the junction of two superconductors shows resonances (the so-called Shapiro steps) which appear at voltages which are multiples of the photon energy of the AC field. Similar resonances for the incoherent (phase-independent) current in a semiconductor SL have been observed in a SL under THz illumination. We here observe a novel coherent Shapiro current in semiconductor superlattices.