Nature Photonics 14, 554–558 (2020)
Photoelectric effect with a twist
Giovanni De Ninno 1,2 ✉, Jonas Wätzel3, Primož Rebernik Ribič 1,2, Enrico Allaria 2,Marcello Coreno2,4, Miltcho B. Danailov2, Christian David5, Alexander Demidovich2,Michele Di Fraia2, Luca Giannessi2,6, Klavs Hansen 7, Špela Krušič8, Michele Manfredda2,Michael Meyer9, Andrej Mihelič8, Najmeh Mirian2, Oksana Plekan2, Barbara Ressel 1,Benedikt Rösner5, Alberto Simoncig2, Simone Spampinati2, Matija Stupar1, Matjaž Žitnik8,Marco Zangrando 2,10, Carlo Callegari2 and Jamal Berakdar3
1 University of Nova Gorica, Nova Gorica, Slovenia.
2 Elettra-Sincrotrone Trieste SCpA, Trieste, Italy.
3 Institut für Physik, Martin-Luther UniversitätHalle-Wittenberg, Halle (Saale), Germany.
4 ISM-CNR, Basovizza Area Science Park, Trieste, Italy.
5 Paul Scherrer Institut, Villigen-PSI, Switzerland.
6 INFN-LNF, Frascati, Rome, Italy.
7 Center for Joint Quantum Studies and Department of Physics, Tianjin University, Tianjin, China.
8 J. Stefan Institute,Ljubljana, Slovenia.
9 European XFEL, Schenefeld, Germany.
10 Istituto Officina dei Materiali, Consiglio Nazionale delle Ricerche, Basovizza, Italy.
Photons have fixed spin and unbounded orbital angular momentum (OAM). While the former is manifested in the polarization of light, the latter corresponds to the spatial phase distribution of its wavefront1. The distinctive way in which the photon spin dictates the electron motion upon light–matter interaction is the basis for numerous well-established spectroscopies. By contrast, imprinting OAM on a matter wave, specifically on a propagating electron, is generally considered very challenging and the anticipated effect undetectable2. In refs. 3,4, the authors provided evidence of OAM-dependent absorption of light by a bound electron. Here, we seek to observe an OAM-dependent dichroic photoelectric effect, using a sample of He atoms. Surprisingly, we find that the OAM of an optical field can be imprinted coherently onto a propagating electron wave. Our results reveal new aspects of light–matter interaction and point to a new kind of single-photon electron spectroscopy.