Petra Hgl University of Regensburg Dr Max Mustermann
Petra Högl University of Regensburg Dr. Max Mustermann Referat Kommunikation & Marketing Verwaltung Magnetoanisotropic Andreev Reflection in Ferromagnet/Superconductor Junctions Petra Högl Alex Matos-Abiague*, Igor Žutić*, Jaroslav Fabian University of Regensburg, Germany *University at Buffalo, USA SFB Workshop – October 5, 2015 Int. Doctorate Program Topological Insulators DFG SFB 689
Petra Högl University of Regensburg Interfacial spin-orbit fields Tunneling anisotropic magnetoresistance (TAMR) Fe Ga. As Au Structure inversion asymmetry Rashba spin-orbit coupling Bulk inversion asymmetry Dresselhaus spin-orbit coupling TAMR ≈ 0. 2% J. Moser, A. Matos-Abiague, D. Schuh, W. Wegscheider, J. Fabian and D. Weiss, PRL 99, 056601 (2007)
Petra Högl University of Regensburg Interfacial spin-orbit fields Tunneling anisotropic magnetoresistance (TAMR) Structure inversion asymmetry Rashba spin-orbit coupling Bulk inversion asymmetry Dresselhaus spin-orbit coupling ? J. Moser, A. Matos-Abiague, D. Schuh, W. Wegscheider, J. Fabian and D. Weiss, PRL 99, 056601 (2007)
Petra Högl University of Regensburg Model: F/S junction with SOC Bogoljubov-de Gennes equation:
Petra Högl University of Regensburg Model: F/S junction with SOC Bogoljubov-de Gennes equation: Ferromagnetic exchange splitting s-wave superconducting coupling Rashba & Dresselhaus spin-orbit coupling
Petra Högl University of Regensburg Model: F/S junction Specular reflection NO spin flip Andreev reflection hole-like quasiparticle electron-like quasiparticle
Petra Högl University of Regensburg Model: F/S junction with SOC Specular reflection NO spin flip Spin-orbit coupling spin flip Andreev reflection hole-like quasiparticle electron-like quasiparticle
Petra Högl University of Regensburg Model: F/S junction with SOC Specular reflection NO spin flip Spin-orbit coupling spin flip Andreev reflection hole-like quasiparticle singlet proxim ity ef electron-like quasiparticle fect triplet proxim ity eff ect
Petra Högl University of Regensburg I. Effect of SOC on: CONDUCTANCE Spin-polarization: Barrier: Rashba SOC: Dresselhaus SOC:
Petra Högl University of Regensburg I. Effect of SOC on: CONDUCTANCE
Petra Högl University of Regensburg II. Magnetoanisotropic Andreev reflection (MAAR) Superconducting analog of TAMR in-plane: out-of-plane:
Petra Högl University of Regensburg In-plane MAAR Zero bias: Spin-polarization: Barrier: Rashba SOC: giant Dresselhaus SOC:
Petra Högl University of Regensburg In-plane MAAR Magnetoanisotropy ≈ G giant G +G isotropic
Petra Högl University of Regensburg In-plane MAAR Magnetoanisotropy ≈ G giant G +G isotropic
Petra Högl University of Regensburg In-plane MAAR Half metal +
Petra Högl University of Regensburg Out-of-plane MAAR Rashba, Dresselhaus Universal MAAR in half metal Spin-polarization: Barrier: Zero bias:
Petra Högl University of Regensburg Out-of-plane MAAR Rashba, Dresselhaus Universal MAAR in half metal Spin-polarization: Barrier: Zero bias:
Petra Högl University of Regensburg Out-of-plane MAAR Rashba, Dresselhaus oop : ip 2: 1 Universal MAAR in half metal Spin-polarization: Barrier: Zero bias:
Petra Högl University of Regensburg Out-of-plane MAAR Rashba, Dresselhaus oop : ip 2: 1 Universal MAAR in half metal Spin-polarization: Barrier: Zero bias:
Petra Högl University of Regensburg Electric field control of spin lifetimes in Nb-Sr. Ti. O₃ by spin -orbit fields (Experiment University of Groningen) Model: Ferromagnetic exchange splitting Rashba spin-orbit field A. M. Kamerbeek, P. Högl, J. Fabian, T. Banerjee, Phys. Rev. Lett. 115, 136601
Petra Högl University of Regensburg Electric field control of spin lifetimes in Nb-Sr. Ti. O₃ by spin -orbit fields (Experiment University of Groningen) Spin-flip current: A. M. Kamerbeek, P. Högl, J. Fabian, T. Banerjee, Phys. Rev. Lett. 115, 136601
Conclusions Thank you Petra Högl University of Regensburg for your a ttention! • Predict magnetoanisotropy of Andreev reflection due to spin-orbit coupling • Giant MAAR amplitudes • Universal MAAR dependence on spin-orbit fields in HM • Propose Andreev reflection spectroscopy as sensitive tool for probing interfacial spin-orbit fields and related magnetoanisotropic phenomena • Magnetization control of Andreev reflection suggests similar control of superconducting proximity effect and Majorana states P. Högl, A. Matos-Abiague, I. Žutić, J. Fabian, Phys. Rev. Lett. 115, 116601 (2015) A. M. Kamerbeek, P. Högl, J. Fabian, T. Banerjee, Phys. Rev. Lett. 115, 136601 (2015)
Petra Högl University of Regensburg Theory for F/S junction with SOC
Petra Högl University of Regensburg Theory for F/S junction with SOC Incoming electron
Petra Högl University of Regensburg Theory for F/S junction with SOC Specular reflection Andreev reflection
Petra Högl University of Regensburg Theory for F/S junction with SOC Specular reflection with spin flip Andreev reflection with spin flip
Petra Högl University of Regensburg Theory for F/S junction with SOC hole-like quasiparticle electron-like quasiparticle
Petra Högl University of Regensburg Theory for F/S junction with SOC with spin flip hole-like quasiparticle electron-like quasiparticle
Petra Högl University of Regensburg Matching conditions Rashba & Dresselhaus spin-orbit coupling
Petra Högl University of Regensburg Conductance
Petra Högl University of Regensburg Conductance no spin flip + spin flip
Petra Högl University of Regensburg System parameters Spin polarization Potential barrier Rashba SOC Dresselhaus SOC
Petra Högl University of Regensburg II. Magnetoanisotropic Andreev reflection (MAAR) Zero bias: Spin-polarization: Barrier: Rashba SOC: Dresselhaus SOC:
Petra Högl University of Regensburg II. Magnetoanisotropic Andreev reflection (MAAR)
Petra Högl University of Regensburg Interfacial spin-orbit coupling fields Majorana states = M. Duckheim, P. W. Brouwer, PRB 83, 054513 (2011) S. B. Chung, H. -J. Zhang, X. -L. Qi, S. C. Zhang, ar. Xiv 1011. 6422
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