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SUMMARY:2026 Scott Lectures: Superconducting Spintronics for Racetrack Mem
 ory - Prof Stuart Parkin (Max Planck Institute of Microstructure Physics)
DTSTART:20260227T110000Z
DTEND:20260227T120000Z
UID:TALK245047@talks.cam.ac.uk
CONTACT:Vanessa Bismuth
DESCRIPTION:Superconducting spintronics is a highly interesting area of re
 search which allows\, for example\, for the formation of unconventional su
 perconducting states via proximity induced superconductivity in certain ma
 gnetic materials. \n\nWe have shown that Josephson junctions fabricated fr
 om conventional s-wave superconductors that have barriers formed from an i
 ntrinsic noncollinear antiferromagnet1 or from magnetic multilayers design
 ed to have magnetic layers with orthogonal magnetizations2 show very high 
 supercurrent critical densities that are indicative of the formation of tr
 iplet supercurrents. Another highly interesting finding is the observation
  of a Josephson Diode effect (JDE)3-5 in both lateral and vertical Josephs
 on junctions where the barrier is formed from a material that breaks both 
 time reversal symmetry and inversion symmetry. \n\nThe simplest case is pe
 rhaps that of the pure metal platinum that is magnetized at one surface by
  proximity to an insulating ferromagnet in a direction perpendicular to th
 e supercurrent that is created by niobium electrodes at the opposing surfa
 ce6. \n\nWe find large asymmetries in the supercurrent critical density th
 at increase with decreasing temperature below that of the superconducting 
 ordering temperature of niobium. A more exotic case is where the barrier i
 n lateral Josephson junctions is formed from a type II Dirac semi-metal\, 
 NiTe23. The superconducting critical current density shows large asymmetri
 es for current flowing in opposite directions of up to 80% in the presence
  of small magnetic fields transverse to the supercurrent direction. The ba
 rriers can extend to almost a micron in extent and yet still allow for the
  passage of supercurrents. Similar results are found for barriers formed f
 rom PtTe24. \n\nVertical junctions formed from WTe2 also show a diode-like
  behavior in the presence of a magnetic field but only when the field is a
 long a direction perpendicular to a mirror plane in the orthorhombic cryst
 al structure of this unusual van der Waals material5. The JDE could form a
  novel device for reading magnetic nanoscopic objects at ultra low tempera
 tures. Triplet supercurrents that carry spin angular momentum could potent
 ially be used to manipulate magnetization. \n\nTogether these two supercon
 ducting spintronic effects are highly interesting for potential applicatio
 ns in cryogenic logic and memory that could support quantum computing syst
 ems. One of the most interesting applications is for a novel cryogenic for
 m of racetrack memory7*.\n\nReferences:\n1: Jeon\, K.-R. et al. Long-range
  supercurrents through a chiral non-collinear antiferromagnet in lateral J
 osephson junctions. Nat. Mater. 20\, 1358–1363 (2021). https://doi.org/1
 0.1038/s41563-021-01061-9\n2: Kindiak\, I.\, Mishra\, S. S.\, Migliorini\,
  A.\, Pal\, B. & Parkin\, S. S. P. Reduced decay in Josephson coupling acr
 oss ferromagnetic junctions with spin–orbit coupling layers. Appl. Phys.
  Lett. 125\, 082601 (2024). https://doi.org/10.1063/5.0214835\n3: Pal\, B.
  et al. Josephson diode effect from Cooper pair momentum in a topological 
 semimetal. Nat. Phys. 18\, 1228–1233 (2022). https://doi.org/10.1038/s41
 567-022-01699-5\n4: Sivakumar\, P. K. et al. Long-range Phase Coherence an
 d Second Order φ_0-Josephson Effect in a Dirac Semimetal 1T-PtTe2 Comm. P
 hys. 7\, 354 (2024). https://doi.org/10.1038/s42005-024-01825-0\n5: Kim\, 
 J.-K. et al. Intrinsic supercurrent non-reciprocity coupled to the crystal
  structure of a van der Waals Josephson barrier. Nat. Commun. 15\, 1120 (2
 024). \n6: Jeon\, K.-R. et al. Zero-field polarity-reversible Josephson su
 percurrent diodes enabled by a proximity-magnetized Pt barrier. Nat. Mater
 . 21\, 1008–1013 (2022). \n7: Jeon\, J.-C.\, Migliorini\, A.\, Yoon\, J.
 \, Jeong\, J. & Parkin\, S. S. P. Multi-core memristor from electrically r
 eadable nanoscopic racetracks. Science 386\, 315–322 (2024). https://doi
 .org/10.1126/science.adh3419
LOCATION:Lecture Theatre\, Level 2\, Ray Dolby Centre\, Cavendish Laborato
 ry\, JJ Thomson Avenue\, CB3 0US
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