Past colloquia and seminars


GeTe(111) ferroelectric and (GeMn)Te multiferroic Rashba semiconductor: a novel paradigm for spintronic applications

General public Seminar

Manipulating spin textures through magnetic or electric fields is a timely issue due to the potential for applications in low power electronics. Ferromagnetic semiconductors have received continued attention because of the novelty of their fundamental properties and their use as a basis of future semiconductor spintronic technologies. In this respect a novel class of materials based on ferroelectric GeTe(111) enabled to combine ferroelectric order with Rashba type switching of spin textures at room temperatures [1]. With low Mn-dopings the system is expanding its functional properties by becoming also ferromagnetic below a TN~110 K. This novel class of materials, called multiferroic Rashba semiconductors, promise not only integration of ferromagnetic and semiconducting properties [2-4], but due to ferroelectricity from the host α-GeTe(111) they display Rashba-Zeeman type spin splitting coupled to ferroelectric order, with evidence of effective magnetoelectric coupling [5]. The system thus constitutes an intriguing route for a non-volatile and static electrical control of the spin degrees of freedom. Soft x-ray and VUV angle resolved photoemission studies in spin and momentum-resolved ways show that α-GeTe(111) is a narrow band gap semiconductor with three dimensional Rashba-type band structure, reaching to this date unprecedented experimentally verified magnitude of Rashba-splitting with fully spin polarised bulk states near the Fermi level. We recently expanded these experiments to low photon energies (7 eV), which calls for additional laser-based studies to investigate the unoccupied α GeTe(111) and (GeMn)Te states near the Fermi level and their time-resolved properties.

[1] D. Di Sante et al., Electric Control of the Giant Rashba Effect in Bulk GeTe, Adv. Mater. (2012)
[2] J. Krempaský et al., Disentangling bulk and surface Rashba effects in ferroelectric α-GeTe, PRB 94, 205111 (2016)
[3] J. Krempaský et al., Spin-resolved electronic structure of ferroelectric a-GeTe and multiferroic (GeMn)Te, Journal of Physics and Chemistry of Solids, 0022-3697, (2017)
[4] J. Krempaský et al., Entanglement and manipulation of the magnetic and spin–orbit order in multiferroic Rashba semiconductors, Nat. Commun. 7, 13071 (2016)
[5] J. Krempaský et al., Operando imaging of all-electric spin texture manipulation in ferroelectric and multiferroic Rashba semiconductors, PRX 8, 021067 (2018)

When? 05.12.2018 11:00 - 12:00
Where? PER 08 0.58.5, bâtiment de Physique
Chemin du Musée 3
1700 Fribourg
speaker Juraj Krempasky, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
Contact Prof. Dr. Claude Monney
chemin du Musée 3
1700 Fribourg
026 300 9163 3