Rashba materials have appeared as an ideal playground for spin-to-charge conversion in prototype spintronics devices. Among them, α-GeTe(111) is a non-centrosymmetric ferroelectric semiconductor for which a strong spin-orbit interaction gives rise to giant Rashba coupling. Its room temperature ferroelectricity was recently demonstrated as a route towards a new type of highly energy-efficient non-volatile memory device based on switchable polarization. Currently based on the application of an electric field, the writing and reading processes could be outperformed by the use of femtosecond light pulses requiring exploration of the possible control of ferroelectricity on this timescale. Here, we probe the room temperature transient dynamics of the electronic band structure of α-GeTe(111) using time and angle-resolved photoemission spectroscopy. Our experiments reveal an ultrafast modulation of the Rashba coupling mediated on the fs timescale by a surface photovoltage, namely an increase corresponding to a 13% enhancement of the lattice distortion. This opens the route for the control of the ferroelectric polarization in α-GeTe(111) and ferroelectric semiconducting materials in quantum heterostructures.

Département de Physique and Fribourg Center for Nanomaterials Université de Fribourg CH 1700 Fribourg Switzerland

Fritz Haber Institute of the Max Planck Society Faradayweg 4 6 14195 Berlin Germany

Institut für Halbleiter und Festkörperphysik Johannes Kepler Universität A 4040 Linz Austria

Institut für Optik und Atomare Physik Technische Universität Berlin Straße des 17 Juni 135 10623 Berlin Germany

Institut Jean Lamour UMR 7198 CNRS Université de Lorraine Campus ARTEM 2 allée André Guinier BP 50840 54011 Nancy France

Institute of physics Ecole Polytechnique Fédérale de Lausanne CH 1015 Lausanne Switzerland

New Technologies Research Center University of West Bohemia Plzen Czech Republic

Photon Science Division Paul Scherrer Institut CH 5232 Villigen Switzerland

Université Paris Saclay CNRS Centre de Nanosciences et de Nanotechnologies 91120 Palaiseau France

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