Atomic-scale tailoring of spin susceptibility via non-magnetic spin-orbit impurities

Womack, F. N.; Adams, P. W.; Nam, Haewoon; Shih, Chih‐Kang; Catelani, Gianluigi

doi:10.1038/s42005-018-0079-3

“…In most circumstances, however, the orbital response of the superconductor dominates its critical field behavior in the sense that the Zeeman critical field can be an order of magnitude larger that its orbital counterpart. This is particularly true in high spin-orbit scattering superconductors such as Nb and Pb due to the fact that even relatively modest spin-orbit scattering rates can dramatically quench the Zeeman response [18]. But if one makes a low atomic mass film, such as Al, sufficiently thin and orients the field parallel to the film surface then the orbital response will be suppressed and one can realize a purely Zeeman-mediated critical field transition [19].…”

Section: Resultsmentioning

confidence: 99%

Critical field behavior of a multiply connected superconductor in a tilted magnetic field

Womack

¹

,

Adams

²

,

Valles

³

et al. 2019

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We report magnetotransport measurements of the critical field behavior of thin Al films deposited onto multiply connected substrates. The substrates were fabricated via a standard electrochemical process that produced a triangular array of 66 nm diameter holes having a lattice constant of 100 nm. The critical field transition of the Al films was measured near Tc as a function of field orientation relative to the substrate normal. With the field oriented along the normal (θ = 0), we observe reentrant superconductivity at a characteristic matching field Hm = 0.22 T, corresponding to one flux quantum per hole. In tilted fields, the position H * of the reentrance feature increases as sec(θ), but the resistivity traces are somewhat more complex than those of a continuous superconducting film. We show that when the tilt angle is tuned such that H * is of the order of the upper critical field Hc, the entire critical region is dominated by the enhanced dissipation associated with a submatching perpendicular component of the applied field. At higher tilt angles a local maximum in the critical field is observed when the perpendicular component of the field is equal to the matching field. :1911.11424v1 [cond-mat.supr-con] arXiv

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“…In most circumstances, however, the orbital response of the superconductor dominates its critical field behavior in the sense that the Zeeman critical field can be an order of magnitude larger that its orbital counterpart. This is particularly true in high spin-orbit scattering superconductors such as Nb and Pb due to the fact that even relatively modest spin-orbit scattering rates can dramatically quench the Zeeman response [18]. But if one makes a low atomic mass film, such as Al, sufficiently thin and orients the field parallel to the film surface then the orbital response will be suppressed and one can realize a purely Zeeman-mediated critical field transition [19].…”

mentioning

confidence: 99%

Spin-Polarized Tunneling in Critically Disordered Be-Al Bilayers

Womack,

Adams,

Catelani

2020

Preprint

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We report spin-polarized tunneling density of states measurements of the proximity modulated superconductor-insulator transition in ultra thin Be-Al bilayers. The bilayer samples consisted of a Be film of varying thickness, dBe = 0.8 − 4.5 nm, on which a 1 nm thick capping layer of Al was deposited. Detailed measurements of the Zeeman splitting of the BCS coherence peaks in samples with sheet resistances R ∼ h/4e 2 revealed a super-linear Zeeman shift near the critical field. Our data suggests that critically disordered samples have a broad distribution of gap energies and that only the higher portion of the distribution survives as the Zeeman critical field is approached. This produces a counter-intuitive field dependence in which the gap apparently increases with increasing parallel field.

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