Bulk rhombohedral Bi at ambient pressure is a well-known semimetal, and its transition to a superconductor has not been observed, at least down to 50 mK. We report that, unlike bulk rhombohedral Bi, granular Bi nanowires with well-defined rhombohedral grains of approximately 10 nm diameter, fabricated by electrochemically depositing Bi into porous polycarbonate membranes at ambient pressure, are superconducting with two transition temperatures, Tc, of 7.2 and 8.3 K. These Tc values coincide with Tc values of the high-pressure phases Bi-III and Bi-V, respectively. Analysis of our structural and transport data indicates that the superconductivity in granular Bi nanowires probably arises from grain boundary areas where there are structural reconstructions between the grains showing a preferred orientation within a small angular distribution.

Observation of superconductivity in granular bi nanowires fabricated by electrodeposition.

Studies on photoelectrochemical (PEC) cell formed with SILAR deposited Bi2Se3-Sb2Se3 multilayer thin films

Using the generalized time-dependent Ginzburg-Landau equations for dirty superconductors nearT

 c
 we study the oscillatory phase-slip solutions in quasione-dimensional superconductors at arbitrary pair-breaking parameter and calculate their properties. For small pair breaking (“low temperature”), a static approximation can be used, which allows analytic evaluation of most quantities and connects the theory to simple models. The influence of two types of short weak regions that pin the phase slips is considered. They tend to decrease the differential resistance and influence its temperature dependence.

Structure and properties of the dissipative phase-slip state in narrow superconducting filaments with and without inhomogeneities

Quantum Griffiths singularity was theoretically proposed to interpret the phenomenon of divergent dynamical exponent in quantum phase transitions. It has been discovered experimentally in three-dimensional (3D) magnetic metal systems and two-dimensional (2D) superconductors. But, whether this state exists in lower dimensional systems remains elusive. Here, we report the signature of quantum Griffiths singularity state in quasi-one-dimensional (1D) Ta2PdS5 nanowires. The superconducting critical field shows a strong anisotropic behavior and a violation of the Pauli limit in a parallel magnetic field configuration. Current-voltage measurements exhibit hysteresis loops and a series of multiple voltage steps in transition to the normal state, indicating a quasi-1D nature of the superconductivity. Surprisingly, the nanowire undergoes a superconductor-metal transition when the magnetic field increases. Upon approaching the zero-temperature quantum critical point, the system uncovers the signature of the quantum Griffiths singularity state arising from enhanced quenched disorders, where the dynamical critical exponent becomes diverging rather than being constant.

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G. Slama

Papers

The influence of the electron mean free path on phase-slip centers in indium whiskers