Dresden 2009 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 5: Postersession Superconductivity: Materials - Fabrication and Properties

TT 5.14: Poster

Montag, 23. März 2009, 13:00–16:45, P1A

Inducing Superconductivity with Picosecond Pressure Pulses in a Quasi-2D Organic Salt — •Julia Stähler, Arzhang Ardavan, and Andrea Cavalleri — University of Oxford, Department of Physics, Clarendon Laboratory, Parks Rd, Oxford OX1 3PU, UK

The quasi-2D organic compounds of the BEDT-TTF family are prototype materials for unconventional superconductivity. In particular, the κ-(BEDT-TTF)₂Cu[N(CN)₂]Cl exhibits a very rich phase diagram including a pressure-driven antiferromagnetic insulating to superconducting (AF-SC) phase transition below 13 K. So far, all studies of organic superconductors focused on the equilibrium properties of these materials, i.e. the system’s response to slow adiabatic changes of the environment. The present work, however, aims at investigating the dynamic formation of the SC phase after excitation of a picosecond pressure transient using femtosecond laser pulses: The laser intensity is absorbed and leads to a significant local temperature increase at constant volume. As a direct consequence, a pressure pulse is launched in the material. This coherent acoustic pulse traverses through the sample at the speed of sound and is expected to induce the AF-SC phase transition. This phase transition will lead to noticeable changes of the sample’s conductivity and therefore affect the dielectric function є(ω) of the material. In particular, at low energies in the region of the superconducting gap, a significant variation of reflectivity is anticipated. Thus, we employ THz radiation(1 THz = 4 meV) as a probe of the superconducting state. Picosecond time resolution is realized by tuning the time delay between pump laser pulse and THz pulse.