Dresden 2014 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 80: Surface Dynamics I

O 80.10: Vortrag

Donnerstag, 3. April 2014, 18:15–18:30, GER 38

Ultrafast hot electron dynamics at the SrTiO₃-vacuum interface — •Marc Herzog, Daniel Wegkamp, Julia Stähler, and Martin Wolf — Abteilung Physikalische Chemie, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin

In the last decade many surprising properties have been observed at SrTiO₃-related oxide interfaces (e.g. metal-insulator transitions, superconductivity, large magnetoresistance) which originate from metallic states at the STO interface also referred to as quasi two-dimensional electron gas (2DEG). Due to the various exotic properties SrTiO₃ (STO) promises many applications in future oxide electronics. Recently, a 2DEG has been discovered even at the vacuum-cleaved surface of STO.

In order to gain insight into the role of electron interaction/correlation in the 2DEG we have studied the surface-confined electrons in STO by means of time- and angle-resolved photoemission spectroscopy (trARPES) and two-photon photoemission (2PPE) mapping the photoinduced dynamics of occupied and unoccupied electronic states, respectively. The ultrafast response of the 2DEG to below- and above-bandgap laser-pulse excitation reveals energy-dependent electron lifetimes below 60 fs which is much shorter than in 3D metals (e.g. Cu, Ag). These results suggest that electron screening may be strongly suppressed in the 2DEG. Moreover, we discuss the effect of transient surface photovoltage.