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Ciccarelli Group - Spin Physics and Devices


Great part of the energy needed to run a processor is wasted in the form of heat due to Ohmic losses in its resistive components and circuitry. What makes superconductors very attractive more than 100 years from their discovery is the fact that an electrical current can flow indefinitely without loosing any energy via Ohmic losses. Substituting resistive components with superconducting ones in data centres would bring significant energy savings despite the energy needed to keep the temperature down (room-temperature superconductivity is still to be found). In this project in collaboration with the Department of Materials Science in Cambridge, we seek ways to design superconducting and non-volatile spintronic devices that are able to store and process spin-bits with significant energy savings.

REVIEW: APL Materials 9, 050703 (2021)

Conventional superconductivity and magnetism were long believed to be mutually exclusive. In conventional s-wave superconductors, Cooper pairs are in a singlet state and are therefore inadequate for carrying spin-information. We found that the break of time symmetry in combination with the spin-orbit coupling induces the condensation of Cooper pairs that are in a spin-polarised triplet state. These triplet Cooper pairs act as efficient and dissipationless spin channels for a spin current injected by a nearby ferromagnet.

Nature Materials 17, 499–503 (2018)

In heterostructures in which the superconductor (Nb) is sandwiched between a ferromagnet and heavy metal (Pt) the breaking of time reversal symmetry is guaranteed at the interface with the ferromagnet, while the spin-orbit coupling is provided by the heavy atoms at the interface with the paramagnet.

Physical Review B 99, 024507 (2019)


This is an example of a spintronic device which working principle relies on the condensation of spin-polarised triplet Cooper pairs. A ferromagnetic thin film acts as channel for propagating spin waves. It is in contact with a superconductor, which acts as gate, modulating the propagation length of the spin-waves. The propagation length becomes shorter when spin polarised Cooper pairs are present because spin angular momentum is dissipated more easily.

Physical Review X 10, 031020 (2020)

We are interested in studying the limiting speed at which the superconducting spintronic devices can operate. To measure them we rely on different experimental techniques with higher time resolution. Time-resolved THz transmission spectroscopy is an excellent way to measure the superconducting gap with sub-picosecond time resolution. This allows us to monitor how the superconducting spintronic device responds to fast stimuli. The graph on the right shows the opening of the superconducting gap in superconductor MgB2 as a function of temperature, measured with THz transmission spectroscopy. Simultaneously, the electrical resistance drops.