Researchers advance topological superconductors for quantum computing

Nanowerk  September 21, 2023 The interface between 2D topological Dirac states and an s-wave superconductor is expected to support Majorana-bound states (MBS) that can be used for quantum computing applications. Realizing these novel states of matter and their applications requires control over superconductivity and spin-orbit coupling to achieve spin-momentum-locked topological interface states (TIS) which are simultaneously superconducting. A team of researchers in the US (Oak Ridge National Laboratory, Rutgers State University of New Jersey) have shown superconductivity in monolayer (ML) FeTe1–ySey (Fe(Te,Se)) grown on Bi2Te3 by molecular beam epitaxy (MBE). Spin and angle-resolved photoemission spectroscopy (SARPES) directly resolved the interfacial […]

Team creates simple superconducting device that could dramatically cut energy use in computing

Phys.org  July 28, 2023 Accomplishing unequal supercurrents in the forward and backward directions in superconductors would enable unprecedented functionalities. This nonreciprocity of critical supercurrents is called the superconducting (SC) diode effect. An international team of researchers (USA – MIT, US Army DEVCOM, High School (Alabama, Washington). Switzerland, Spain) demonstrated the strong SC diode effect in conventional SC thin films, such as niobium and vanadium, employing external small magnetic fields. Interfacing the SC layer with a ferromagnetic semiconductor EuS, they further accomplished the nonvolatile SC diode effect reaching an efficiency of 65%. By careful control experiments and theoretical modeling, they demonstrated […]

Researchers achieve interdimensional superconductivity

Nanowerk  July 19, 2023 Spatial disorder has been shown to drive two-dimensional (2D) superconductors to an insulating phase through a superconductor–insulator transition (SIT). Numerical calculations predict that with increasing disorder, emergent electronic granularity is expected in these materials—a phenomenon where superconducting (SC) domains on the scale of the material’s coherence length are embedded in an insulating matrix and coherently coupled by Josephson tunneling. An international team of researchers (USA – SLAC National Accelerator Laboratory, Colombia) has shown spatially resolved scanning tunneling spectroscopy (STS) measurements of the three-dimensional (3D) superconductor BaPb1−xBixO3 (BPBO), which surprisingly demonstrated three key signatures of emergent electronic […]

The exciting possibilities of tiny, twisted superconductors

Phys.org  May 5, 2023 A team of researchers in the USA (Rutgers University, Harvard University, University of Connecticut, Louisiana State University, Flatiron Institute, Princeton University) proposed how to experimentally manipulate the quasiparticles, in very thin layers of ordinary superconductors to create topological superconductors by slightly twisting the stacked layers. They theorized that the application of a current makes the quasiparticles in the superconductor behave as if they were in a topological superconductor. They theorized that the twist at any angle essentially determines the properties. Even deviations by .1 degree in twist is strongly detrimental. The interactions between quasiparticles are shown […]

Electrons take new shape inside unconventional metal

Phys.org  January 10, 2023 After an extensive study of the angular dependence of quantum oscillations (QOs) in the electrical conductivity of YPtBi an international team of researchers (USA – University of Maryland, Missouri University of Science and Technology, Rutgers University, Canada) has reported an anomalous Shubnikov–de Haas effect consistent with the presence of a coherent j=3/2 Fermi surface. The QO signal in YPtBi manifested an extreme anisotropy upon rotation of the magnetic field from the [100] to [110] crystallographic direction, where the QO amplitude vanished. According to the researchers this radical anisotropy for such a highly isotropic system cannot be […]

The magneto-optic modulator

EurekAlert  September 16, 2022 Superconducting microprocessors and quantum computers promise to revolutionize computation, but ultra-cold components must interface with ambient temperature systems. An international team of researchers (USA – UC Santa Barbara, industry, Italy, UK, Japan) has built a device that translates electrical input into pulses of light. An electric current creates a magnetic field that changes the refractive index of a synthetic garnet making it possible to tune the amplitude of the light that circulates in a micro-ring resonator. This creates bright and dark pulses that carry information through the fiberoptic cable. The modulator operates at wavelengths of 1,550 […]

Terahertz light from superconducting stripes

Phys.og  September 22, 2022 The interplay between charge order and superconductivity remains one of the central themes of research in quantum materials. In the case of cuprates, the coupling between striped charge fluctuations and local electromagnetic fields is especially important, as it affects transport properties, coherence, and dimensionality of superconducting correlations. An international team of researchers (Germany, USA – Harvard University, Brookhaven National Laboratory, Switzerland, UK) studied the emission of coherent terahertz radiation in single-layer cuprates of the La2-xBaxCuO4 family, for which this effect is expected to be forbidden by symmetry. They found that emission vanishes for compounds in which […]

A proof of odd-parity superconductivity

Phys.org  July 12, 2022 Odd-parity superconductivity is rare in nature; only a few materials support this state, and in none of them has the expected angle dependence been observed. CeRh2As2 was recently found to exhibit two superconducting states: A low-field state changes into a high-field state at 4 T when a magnetic field is applied along one axis. Through a comprehensive study of the angle dependence of the upper critical fields using magnetic ac susceptibility, specific heat, and torque on single crystals of CeRh2As2 an international team of researchers (Germany, New Zealand, France, USA – University of Wisconsin) has shown […]

Researchers find a way to form diodes from superconductors

Science Daily  May 11, 2022 An international team of researchers (Italy, Spain, USA – MIT) has developed the quasi-particle counterpart, a superconducting tunnel diode with zero conductance in only one direction. The direction-selective propagation of the charge was obtained through the broken electron-hole symmetry induced by the spin selection of the ferromagnetic tunnel barrier: a EuS thin film separating a superconducting Al and a normal metal Cu layer. The Cu/EuS/Al tunnel junction achieved a large rectification (up to ∼40%) already for a small voltage bias (∼200 μV) due to the small energy scale of the system. With the help of an […]

Study shows how superconductivity can be switched on and off in superconductors

Phys.org  March 30, 2022 Recent experiments have suggested that superconductivity in metallic nanowires can be suppressed by the application of modest gate voltages. The source of this gate action has been debated and either attributed to an electric-field effect or to small leakage currents. An international team of researchers (Switzerland, Italy, USA – IBM, NY) has shown that the suppression of superconductivity in titanium nitride nanowires on silicon substrates does not depend on the presence or absence of an electric field at the nanowire but requires a current of high-energy electrons. The suppression is most efficient when electrons are injected […]