Enhancement of superconductivity in MgB${}_2$ by narrow-band THz pumping

First observations of amplified superconductivity by electromagnetic radiation at sub-gap frequencies date back to late 1960's. These works reported an increase of the gap and the superconducting transition temperature in type-I superconductors Al and Sn. Recently, enhancement effects have also been observed in NbN by using picosecond narrow-band THz pulses, tuned to the vicinity of the superconducting gap frequency. Here we report on systematic studies of the superconducting gap dynamics in MgB${}_2$. Tuning the pump frequency between the two superconducting gap energies in this two-band superconductor we observe strong superconducting enhancement effects competing with THz driven pair-breaking. For temperatures close to the transition temperature (T${}_c$ = 36 K) the enhancement effects seem to dominate, giving rise to a global amplification of superconductivity.