High-order nonlinear terahertz probing of the two-band superconductor MgB2: Third- and fifth-order harmonic generation

We report on high-order harmonic generation in the two-band superconductor MgB2 driven by intense terahertz electromagnetic pulses. Third-and fifth-order harmonics are resolved in time domain and investigated as a function of temperature and in applied magnetic fields crossing the superconducting phase boundary. The high-order harmonics in the superconducting phase reflects nonequilibrium dynamics of the superconducting order parameter in MgB2, which is probed via nonlinear coupling to the terahertz field. The observed temperature and field dependence of the nonlinear response allows to establish the superconducting phase diagram.

Automated summary

In this study, high-order harmonic generation in the two-band superconductor MgB2 driven by intense terahertz electromagnetic pulses is reported. The nonequilibrium dynamics of the superconducting order parameter in MgB2 is probed via the nonlinear coupling to the terahertz field, which is reflected by the observed high-order harmonics in the superconducting phase. The temperature and field dependence of the nonlinear response allows for the establishment of the superconducting phase diagram.