Tunable superconducting critical temperature in ballistic hybrid structures with strong spin-orbit coupling

Abstract

We present a theoretical description and numerical simulations of the superconducting transition in hybrid structures including strong spin-orbit interactions. The spin-orbit coupling is taken to be of Rashba type for concreteness, and we allow for an arbitrary magnitude of the spin-orbit strength as well as an arbitrary thickness of the spin-orbit coupled layer. This allows us to make contact with the experimentally relevant case of enhanced interfacial spin-orbit coupling via atomically thin heavy metal layers. We consider both interfacial spin-orbit coupling induced by inversion asymmetry in an S/F-junction, as well as in-plane spin-orbit coupling in the ferromagnetic region of an S/F/S-and an S/F-structure. Both the pair amplitudes, local density of states and critical temperature show dependency on the Rashba strength and, importantly, the orientation of the exchange field. In general, spin-orbit coupling increases the critical temperature of a proximity system where a magnetic field is present, and enhances the superconducting gap in the density of states. We perform a theoretical derivation which explains these results by the appearance of long-ranged singlet correlations. Our results suggest that T c in ballistic spin-orbit coupled superconducting structures may be tuned by using only a single ferromagnetic layer.

Supercurrent in ferromagnetic Josephson junctions with heavy-metal interlayers. II. Canted magnetization

“…Several theoretical studies have shown that spin-orbit coupling can act to convert spin-singlet correlations into equal-spin triplet correlations, potentially removing the need for ferromagnetic spin-mixer layers in Josephson junctions [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. Recent experimental studies show modification to the standard S -F proximity effect in the presence of additional spin-orbit coupling layers [30][31][32][33].…”

Enhanced spin-triplet pairing in magnetic junctions with s -wave superconductors

“…While we employ a simple approach which naturally suggests a number of generalizations, from inclusion of the self-consistent pair potential, finite B-fields, study of critical temperature, or more complex barrier description [42][43][44][45][46][47], its transparency already reveals several important trends and can support peculiar experimental observation of a giant MAAR [40]. Our implications for enhanced triplet pairing and MAAR detection could also be relevant for two-dimensional materials, as supported by the work in Refs.…”

Magnetic control of superconducting heterostructures using compensated antiferromagnets

“…Previous studies have suggested introducing heavy-metal layers boosting the interfacial Rashba spin-orbit coupling in a S/F bilayer [11][12][13][14][15][16][17]. The Rashba spin-orbit field introduces additional symmetry breaking [18] that allows for control over the spin-triplet channels when rotating the magnetization of the single ferromagnetic layer.…”