Event Details

Condensed Matter seminar

In this talk I will give an overview of the group’s activities.

I will start by discussing some recent work in collaboration with the Department of Material Science and Metallurgy in Cambridge on superconducting spintronics. We have carried a series of spin pumping experiments in different ferromagnet-superconductor proximity structures [1] and found the conditions for efficient spin transfer into the superconductor. This seems to be in contrast with the BCS theory of conventional superconductivity, where Cooper pairs are assumed to be in a singlet state and thus cannot carry any spin. We attribute the enhanced spin transfer to the condensation of spin polarised triplet Cooper pairs when time inversion symmetry is combined with the spin-orbit coupling [2].

In the second part of the talk, I will discuss our studies on spin to charge conversion or the electrical readout of magnons. I will start by discussing systems in which space inversion symmetry is internally broken and in which the spin-orbit-coupling establishes a direct connection between charge and spin, reflected for example by the known spin-orbit torques [3] or in its less known reciprocal effect, magnon charge pumping [4]. Another way to convert magnons into an electrical signal is to transfer them to an external spin-to-charge transducer like a heavy metal, by a temperature gradient for example (the spin-Seebeck effect). I will discuss our studies on the spin-Seebeck effect at picosecond timescales using time-resolved THz emission spectroscopy [5]. At these timescales the energy exchange processes that determine the flow of spin from the magnet to the adjacent heavy metal are very different from those considered in the quasi-static measurements reported so far end result in a different temperature dependence.

[1] APL Materials 9, 050703 (2021)

[2] Nature Materials 17, 499 (2018)

[3] Nature Physics 12, 855(2016)

[4] Nature Nanotechnology 10, 50 (2015)

[5] Appl. Phys. Lett. 119, 032401 (2021)

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