Tunable critical field in Rashba superconductor thin-films

The upper critical field in type II superconductors is limited by the Pauli paramagnetic limit. In superconductors with strong Rashba spin-orbit coupling this limit can be overcome by forming a helical state. Here we quantitatively study the magnetic field-temperature phase diagram of finite-size superconductors with Rashba spin-orbit coupling. We discuss the effect of finite size and shape anisotropy. We demonstrate that the critical field is controllable by intrinsic parameters such as spin-orbit coupling strength and tunable parameters such as sample geometry and applied field direction. Our study opens new avenues for the design of superconducting spin-valves

Large‐scale on‐chip integration of gate‐voltage addressable hybrid superconductor–semiconductor quantum wells field effect nano‐switch arrays

Stable, reproducible, scalable, addressable, and controllable hybrid superconductor–semiconductor (S–Sm) junctions and switches are key circuit elements and building blocks of gate-based quantum processors. The electrostatic field effect produced by the split gate voltages facilitates the realization of nano-switches that can control the conductance or current in the hybrid S–Sm circuits based on 2D semiconducting electron systems. Here, a novel realization of large-scale scalable, and gate voltage controllable hybrid field effect quantum chips is experimentally demonstrated. Each chip contains arrays of split gate field effect hybrid junctions, that work as conductance switches, and are made from In0.75Ga0.25As quantum wells integrated with Nb superconducting electronic circuits. Each hybrid junction in the chip can be controlled and addressed through its corresponding source–drain and two global split gate contact pads that allow switching between their (super)conducting and insulating states. A total of 18 quantum chips are fabricated with 144 field effect hybrid Nb- In0.75Ga0.25As 2DEG-Nb quantum wires and the electrical response, switching voltage (on/off) statistics, quantum yield, and reproducibility of several devices at cryogenic temperatures are investigated. The proposed integrated quantum device architecture allows control of individual junctions in a large array on a chip useful for emerging cryogenic quantum technologies

Evidence for spin mixing in holmium thin film and crystal samples

144518Quantum Matter and Optic

Josephson Coupling and Fiske Dynamics in Ferromagnetic Tunnel Junctions

We report on the fabrication of Nb/AlO_x/Pd_{0.82}Ni_{0.18}/Nb superconductor/insulator/ferromagnetic metal/superconductor (SIFS) Josephson junctions with high critical current densities, large normal resistance times area products, high quality factors, and very good spatial uniformity. For these junctions a transition from 0- to \pi-coupling is observed for a thickness d_F ~ 6 nm of the ferromagnetic Pd_{0.82}Ni_{0.18} interlayer. The magnetic field dependence of the \pi-coupled junctions demonstrates good spatial homogeneity of the tunneling barrier and ferromagnetic interlayer. Magnetic characterization shows that the Pd_{0.82}Ni_{0.18} has an out-of-plane anisotropy and large saturation magnetization, indicating negligible dead layers at the interfaces. A careful analysis of Fiske modes provides information on the junction quality factor and the relevant damping mechanisms up to about 400 GHz. Whereas losses due to quasiparticle tunneling dominate at low frequencies, the damping is dominated by the finite surface resistance of the junction electrodes at high frequencies. High quality factors of up to 30 around 200 GHz have been achieved. Our analysis shows that the fabricated junctions are promising for applications in superconducting quantum circuits or quantum tunneling experiments.Comment: 15 pages, 9 figure

Tunable critical field in Rashba superconductor thin films

Strong intrinsic or interfacial spin-orbit coupling (SOC) can enable a thin-film superconductor to exceed the paramagnetic limit. For Rashba-type SOC, we show that the superconducting thermodynamic properties of a finite-size thin film are strongly sample-size dependent due to the creation of edge states; for example, in the case of geometrically anisotropic thin films, the critical field is found to be tunable through the direction of an externally applied in-plane magnetic field. These findings open perspectives for the development of superconducting spin-orbitronic devices

Tunable critical field in Rashba superconductor thin-films

The upper critical field in type II superconductors is limited by the Pauli paramagnetic limit. In superconductors with strong Rashba spin-orbit coupling this limit can be overcome by forming a helical state. Here we quantitatively study the magnetic field-temperature phase diagram of finite-size superconductors with Rashba spin-orbit coupling. We discuss the effect of finite size and shape anisotropy. We demonstrate that the critical field is controllable by intrinsic parameters such as spin-orbit coupling strength and tunable parameters such as sample geometry and applied field direction. Our study opens new avenues for the design of superconducting spin-valves

Tunable critical field in Rashba superconductor thin films

Strong intrinsic or interfacial spin-orbit coupling (SOC) can enable a thin-film superconductor to exceed the paramagnetic limit. For Rashba-type SOC, we show that the superconducting thermodynamic properties of a finite-size thin film are strongly sample-size dependent due to the creation of edge states; for example, in the case of geometrically anisotropic thin films, the critical field is found to be tunable through the direction of an externally applied in-plane magnetic field. These findings open perspectives for the development of superconducting spin-orbitronic devices

Enhanced localized superconductivity in Sr2RuO4 thin film by pulsed laser deposition

Superconducting c-axis-oriented Sr2RuO4 thin film has been fabricated using pulsed laser deposition. Although the superconductivity is localized, the onset critical temperature is enhanced over the bulk value. X-ray microstructural analysis of Sr2RuO4 superconducting and non-superconducting thin films suggests the existence of the localized stacking faults and an overall c-axis lattice expansion which may account for the locally enhanced superconductivity