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Grey tin, also known as α-Sn, is a nominally zero-gap semiconductor stable below 13°C, in which various topological phases can be induced by external strain  [1, 2]. In particular, the application of biaxial compressive strain transforms α-Sn into a topological Dirac semimetal (DSM), which can be further converted into a Weyl semimetal (WSM) via an external magnetic field. One effective method of strain

Terahertz (THz) radiation, covering frequencies from 300 GHz to 30 THz, enables access to physical, chemical, and biological phenomena that are otherwise difficult to probe, with applications ranging from high-speed communications to medical diagnostics. Spintronic emitters based on ferromagnet/heavy-metal bilayers excited by femtosecond laser pulses have become key broadband THz sources, where emission is driven by the inverse spin Hall effect (ISHE). However, the influence of interfacial properties on spin-to-charge conversion remains an open question. This work introduces tunnel spintronic emitters consisting of a ferromagnetic FeCo layer and a Pt layer separated by an MgO tunnel barrier. Experiments reveal that, unlike conventional bilayers where THz polarization is governed by the ferromagnetic magnetization and tunable with an external field, tunnel emitters exhibit unconventional polarization behavior. These findings point to new interfacial mechanisms that will be discussed.

The lecture will be in English on-site in room 203. ZOOM transmission will be available too.

Zoom information.