Light Control of Superconductivity
Strong electric field transients at terahertz frequencies can be used to control the electronic properties of high-temperature superconductors. In a series of experiments we demonstrated that the superconducting response of high-Tc cuprates and of some alkali-doped fullerides can be transiently enhanced by stimulating with light some specific vibrational degrees of freedom. In addition, resonant excitation of Josephson Plasma modes at millimeter wavelengths has also been shown to be a powerful tool to drive exotic dynamics in layered superconductors.
Phase control in complex oxides
The ground states of strongly correlated electron systems are stabilized by the complex interaction of electronic, magnetic and lattice degrees of freedom. Their nonlinear physics promote a large susceptibility of their macroscopic electronic and magnetic to external perturbations.
The stimulation with light can perturb a stable ground state and induce transient metastable phases - with dramatic rearrangements in the structural, electronic and magnetic properties. These optically driven states are typically ´hidden´ phases, not found in the equilibrium phase diagram. Of particular interest for our group is the selective excitation of one single (vibrational) degree of freedom on low energy scales, in stark contrast to excitation at visible or near-IR wavelengths mostly heating up the electronic systems.