Theory of Andreev reflection spectroscopy with anisotropic spin-dependent scattering

Abstract:Spintronic technologies require efficient generation and control of spin-polarized currents. Conventional ferromagnet-based methods suffer from sensitivity to external magnetic fields. Andreev reflection spectroscopy is vital for measuring spin polarization and superconducting gaps, yet prevailing theories assume isotropic interface scattering. This neglects ubiquitous anisotropy in heterostructures, causing misinterpretation of material properties. To resolve this, we develop a generalized model incorporating spin-dependent anisotropic scattering. Introducing distinct interface barriers for spin-up and spin-down electrons extends both the Blonder-Tinkham-Klapwijk formalism and the Chen-Tesanovic-Chien extension. This unified framework describes transport from normal metals to half-metals. Solving the Bogoliubov-de Gennes equations with modified boundary conditions yields current formulae with a transmission probability judgment function identifying dominant spin channels. In non-magnetic metals, interfacial anisotropy generates sizable spin-polarized currents via transmission spin filtering, suppressing Andreev reflection and reducing sub-gap conductance. For positively polarized ferromagnets, anisotropy nonlinearly modulates polarization, enhancing Andreev reflection to a threshold before suppression. Negatively polarized materials exhibit inverse spectra, enabling unambiguous polarization sign determination via conductance comparisons. Epitaxial Co film measurements validate the model, resolving subtle anisotropies. This refines Andreev spectrum interpretation and supports interference-resistant spin sources using non-magnetic platforms, benefiting magnetoresistive devices and superconducting quantum technologies.

Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Quantum Physics (quant-ph)

arXiv:2607.22747 [cond-mat.mes-hall]

(or arXiv:2607.22747v1 [cond-mat.mes-hall] for this version)

https://doi.org/10.48550/arXiv.2607.22747 Focus to learn more arXiv-issued DOI via DataCite (pending registration)

https://doi.org/10.7498/aps.75.20251669 Focus to learn more DOI(s) linking to related resources

arXivLabs is a framework that allows collaborators to develop and share new arXiv features directly on our website.

Both individuals and organizations that work with arXivLabs have embraced and accepted our values of openness, community, excellence, and user data privacy. arXiv is committed to these values and only works with partners that adhere to them.

Have an idea for a project that will add value for arXiv's community? Learn more about arXivLabs.