Ultrafast Optical Control of Complex Quantum Materials*

It is a well known fact that phase transitions in condensed matter can by triggered by external parameters such as temperature, pressure, electric or magnetic field. Finding systems that show light induced transitions became a particular interesting field of research. Advanced nonlinear optical methods based on pump-probe spectroscopy open new ways of controlling ultrafast dynamics in complex materials on unprecedented timescales. In quantum materials, finding new ways of manipulating the interplay of electronic phases or effectively tuning electronic interactions opens new avenues in controlling physical properties and designing new functionalities.
I will discuss different scenarios like the balancing between competing phases via ultrashort light pulses or possibilities of dynamical stabilization of new states in periodically driven light fields. One finds remarkable possibilities to induce superconductivity in high-Tc cuprate superconductors [1] by melting competing “stripe”-order [2] or promoting SC to temperatures far above Tc [3,4]. Possible light-induced superconductivity in doped fullerides K₃C₆₀ [5] serves as important example that inducing such intriguing effects is a more general effect based on non-linear effective interaction control [6,7]. Going beyond superconductors, for excitonic insulators (a BEC of excitons) probing the coherent response of the order parameter reveals possible couplings to the lattice structure [8].

[1] S. Kaiser, Physica Scripta 92, 1003001 (2017).
[2] D. Fausti et al. Science 331, 189 (2011).
[3] S. Kaiser et al. Phys. Rev. B 89, 184515 (2014).
[4] W. Hu et al. Nature Materials 13, 705 (2014).
[5] M. Mitrano et al. Nature 530, 461 (2016).
[6] S. Kaiser et al., Scientific Reports 6, 3823 (2014).
[7] R. Singla et al., Phys. Rev. Lett. 115, 187401 (2015).
[8] D. Werdehausen et al. arxiv:1607.02314 (2016).