Dresden 2011 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 35: CE: Low-dimensional Systems - Materials 3
TT 35.12: Talk
Wednesday, March 16, 2011, 17:15–17:30, HSZ 301
Vibrational control of Mottness in the organic Mott insulator ET-F2TCNQ — Stefan Kaiser1, •Daniele Nicoletti1, Raanan I. Tobey2, Nicky Dean2, Stefano Lupi3, Hiroshi Okamoto4, Jun'ya Tsutsumi4, Tatsuo Hasegawa4, and Andrea Cavalleri1,2 — 1Max Planck Research Department for Structural Dynamics, Center for Free Electron Laser Science & University of Hamburg, c/o DESY, Hamburg, Germany — 2Department of Physics, Oxford University, UK — 3Department of Physics, University of Rome La Sapienza, Italy — 4AIST, Tsukuba, Japan
Control of on-site electronic wavefunctions is achieved in the organic conductor ET-F2TCNQ by resonant excitation of localized vibrational modes of the ET molecule. Such excitation modulates the on-site Coulomb repulsion and modifies the relative strength of electron correlations and hopping, thus controlling the Mott criterion. We performed pump-probe experiments using optical parametrical amplifiers, with a time resolution of 80 fs. Excitation was achieved with mid-IR pulses from difference frequency mixing, resonant with two different intramolecular vibrations at 10 and 6 microns. The probe was tuned over the whole IR range, in order to trace the reflectivity changes in the charge-transfer band and the possible filling of the Mott gap, thus providing a direct evidence of the control of on-site Coulomb repulsion. Through such mode-selective excitations, the Mott gap can be filled and the system is pushed forward to the less correlated and metallic side. This approach promises a new way of control for electronic and even superconducting properties in correlated electron systems.