Far-infrared absorption of thin superconducting aluminum films in the pair-breaking and paramagnetic limits

P. J. M. van Bentum; P. Wyder

doi:10.1103/PhysRevB.34.1582

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Far-infrared absorption of thin superconducting aluminum films in the pair-breaking and paramagnetic limits

P. J. M. van Bentum, P. Wyder

DOI 10.1103/PhysRevB.34.1582 · Physical Review B

T1

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Abstract

Measurements are presented of the far-infrared absorption of thin superconducting aluminum films in a parallel magnetic field. The results for moderately thick films (d≊10 nm) are in reasonable agreement with the Abrikosov-Gor’kov theory of pair breaking. The experimental results for ultrathin films (d≤5 nm) in the paramagnetic limit show that the spectroscopic gap Ωg shifts linearly with the magnetic field H, according to ħΩg=2Δ-2μ0μBH. This shift of the gap is attributed to a photon-absorption process, where the quasiparticle spin is flipped with respect to the static field. The complex conductivity of a paramagnetically limited film in a parallel magnetic field is calculated, both within the Bardeen-Cooper-Schrieffer framework and using the more general Green’s-function formalism with the inclusion of spin-orbit and (magnetic) spin-flip scattering. For the ultrathin Al films we obtain a good quantitative agreement between theory and experiment, assuming a spin-orbit coupling ħ/τSOΔ≊0.1 and a reduced value of the imaginary part of the conductivity, probably due to strong electron-phonon coupling effects.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
Al Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	1.21	Pressure not reported	unknown
Al Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	1.51	Pressure not reported	unknown
Al Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	2.03	Pressure not reported	unknown
Al Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	1.52	Pressure not reported	unknown
Al Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	3.41	Pressure not reported	unknown
Al Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	1.96	Pressure not reported	unknown
Al Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	2.1	Pressure not reported	unknown