Semiconductor–Ferromagnetic Insulator–Superconductor Nanowires: Stray Field and Exchange Field

Liu, Yu; Vaitiekėnas, S.; Martí‐Sánchez, Sara; Koch, Christian; Hart, Sean; Cui, Zheng; Kanne, Thomas; Khan, Sabbir Ahmed; Tanta, Rawa; Upadhyay, Shivendra; Cachaza, Martin E.; Marcus, C. M.; Arbiol, Jordi; Moler, Kathryn A.; Krogstrup, Peter

doi:10.1021/acs.nanolett.9b04187

Cited by 73 publications

(63 citation statements)

References 59 publications

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“…Recently the first attempts toward zero-external-field topological superconductivity have been made [14,15]. A typical setup of a heterostructure consists of semiconducting (SM), superconducting (SC), and magnetic insulator (MI) parts connected together as shown schematically in Fig.…”

Section: Introductionmentioning

confidence: 99%

“…The authors of Refs. [14,15] further coupled EuS to Al and InAs with the ultimate goal of inducing zero-field topological superconductivity. Epitaxial growth on different wire facets was achieved and the stray magnetic field generated by EuS was found to be insufficient for inducing a topological phase [15].…”

Section: Introductionmentioning

confidence: 99%

“…[14,15] further coupled EuS to Al and InAs with the ultimate goal of inducing zero-field topological superconductivity. Epitaxial growth on different wire facets was achieved and the stray magnetic field generated by EuS was found to be insufficient for inducing a topological phase [15]. Furthermore, conductance spectroscopy revealed a distinctly different behavior for different geometries of the system [14].…”

Section: Introductionmentioning

confidence: 99%

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Topological superconductivity in nanowires proximate to a diffusive superconductor–magnetic-insulator bilayer

et al. 2021

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We study semiconductor nanowires coupled to a bilayer of a disordered superconductor and a magnetic insulator, motivated by recent experiments reporting possible Majorana-zero-mode signatures in related architectures. Specifically, we pursue a quasiclassical Usadel equation approach that treats superconductivity in the bilayer self-consistently in the presence of spin-orbit scattering, magnetic-impurity scattering, and Zeeman splitting induced by both the magnetic insulator and a supplemental applied field. Within this framework we explore prospects for engineering topological superconductivity in a nanowire proximate to the bilayer. We find that a magnetic-insulator-induced Zeeman splitting, mediated through the superconductor alone, cannot induce a topological phase since the destruction of superconductivity (i.e., Clogston limit) preempts the required regime in which the nanowire's Zeeman energy exceeds the induced pairing strength. However, this Zeeman splitting does reduce the critical applied field needed to access the topological phase transition, with fields antiparallel to the magnetization of the magnetic insulator having an optimal effect. Finally, we show that magnetic-impurity scattering degrades the topological phase, and spin-orbit scattering, if present in the superconductor, pushes the Clogston limit to higher fields yet simultaneously increases the critical applied field strength.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Topological superconductivity in nanowires proximate to a diffusive superconductor–magnetic-insulator bilayer

et al. 2021

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“…However, now the quantum system consists of only the InAs nanowire and the Al layer, which we treat on equal footing at the quantum mechanical level. We model the role of EuS as an induced exchange coupling term in the associated regions in InAs and Al, while neglecting the stray field from the EuS [46]. The effects of gates, surface charges, dielectric layers, and the vacuum are taken into account via the self-consistently calculated electrostatic potential inside the InAs nanowire.…”

Section: A Model Hamiltonianmentioning

confidence: 99%

Electronic properties of InAs/EuS/Al hybrid nanowires

et al. 2021

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We study the electronic properties of InAs/EuS/Al heterostructures as explored in a recent experiment [S. Vaitiekėnas et al., Nat. Phys. 17, 43 (2020)], combining both spectroscopic results and microscopic device simulations. In particular, we use angle-resolved photoemission spectroscopy to investigate the band bending at the InAs/EuS interface. The resulting band offset value serves as an essential input to subsequent microscopic device simulations, allowing us to map the electronic wave function distribution. We conclude that the magnetic proximity effects at the Al/EuS as well as the InAs/EuS interfaces are both essential to achieve topological superconductivity at zero applied magnetic field. Mapping the topological phase diagram as a function of gate voltages and proximity-induced exchange couplings, we show that the ferromagnetic hybrid nanowire with overlapping Al and EuS layers can become a topological superconductor within realistic parameter regimes. Our work highlights the need for a combined experimental and theoretical effort for faithful device simulations.

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“…1). The technology for building this setup has already been developed, motivated by the prospects of utilizing MFs as a staple ingredient for topological quantum computers [38][39][40][41][42]. We explore the potential of this setup in a completely different context utilizing the perfect topologically protected Andreev reflection (AR) enabled by the MF [37,43] but not exploiting the existence of a nonlocal quantum degrees of freedom used in topological quantum computers [44].…”

Section: Introductionmentioning

confidence: 99%

Topological charge, spin, and heat transistor

2021

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Spin pumping consists in the injection of spin currents into a nonmagnetic material due to the precession of an adjacent ferromagnet. In addition to the pumping of spin the precession always leads to pumping of heat, but in the presence of spin-orbital entanglement it also leads to a charge current. We investigate the pumping of charge, spin, and heat in a device where a superconductor and a quantum spin Hall insulator are in proximity contact with a ferromagnetic insulator. We show that the device supports two robust operation regimes arising from topological effects. In one regime, the pumped charge, spin, and heat are quantized and related to each other due to a topological winding number of the reflection coefficient in the scattering matrix formalism, translating to a Chern number in the case of Hamiltonian formalism. In the second regime, a Majorana zero mode switches off the pumping of currents owing to the topologically protected perfect Andreev reflection. We show that the interplay of these two topological effects can be utilized so that the device operates as a robust charge, spin, and heat transistor.

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Semiconductor–Ferromagnetic Insulator–Superconductor Nanowires: Stray Field and Exchange Field

Cited by 73 publications

References 59 publications

Topological superconductivity in nanowires proximate to a diffusive superconductor–magnetic-insulator bilayer

Topological superconductivity in nanowires proximate to a diffusive superconductor–magnetic-insulator bilayer

Electronic properties of InAs/EuS/Al hybrid nanowires

Topological charge, spin, and heat transistor

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