We show here that yttrium is immiscible and precipitates with various sizes in the body centered cubic V0.6Ti0.4 alloy superconductor. The number and size of the precipitates are found to depend on the amount of yttrium added. Precipitates with various sizes up to 30 μm are found in the V0.6Ti0.4 alloy containing 5 at. % yttrium. The large amount of line disorders generated by the addition of yttrium in this alloy is found to be effective in pinning the magnetic flux lines. While the superconducting transition temperature increases with the increasing amount of yttrium in the V0.6Ti0.4 alloy, the critical current density is maximum for the alloy containing 2 at. % yttrium, where it is more than 7.5 times the parent alloy in fields higher than 1 T. We found that the effectiveness of each type of defect in pinning the flux lines is dependent on the temperature and the applied magnetic filed.

The V-Ti alloys are promising materials as alternate to the commercial Nb-based superconductors for high currenthigh magnetic field applications. However, the critical current density (Jc) of these alloys are somewhat low due to their low grainboundary density. We show here that grain refinement of the V-Ti alloys and enhancement of the Jc can be achieved by the addition of Gd into the system, which precipitates as clusters along the grain boundaries. Both the Jc and the pinning force density ( ) increase with the increasing Gd content up to 1 At. % Gd, where they are more than 20 times higher than those of the parent V0.60Ti0.40 alloy. Introduction of Gd into the system also leads to ferromagnetic (FM) correlations, and the alloys containing more than 0.5 At. % Gd exhibit spontaneous magnetization. In spite of the FM correlations, the superconducting transition temperature increases slightly with Gd-addition.

The morphological, transport and terahertz optical properties of DC magnetron sputtered granular molybdenum thin-films with nano-grains embedded in an amorphous matrix have been studied in the normal and superconducting states. The superconducting transition temperatures of these films are much higher than that of bulk molybdenum. The optical properties of these thin-films have been studied using terahertz time-domain spectroscopy. Their properties have been compared with the existing materials used for the development of radiation detectors. The resistivity of the films lies in >100 µΩ-cm range which is ideal for making highly sensitive radiation detectors. The Hall measurements indicate the presence of holes as the dominant carriers with very small mean free path and mobility. In the normal state, the films are disordered bad metal but they have large superfluid density and stiffness in their superconducting state. The normal state and superconducting properties of the films are very promising for their use in cryogenic radiation detectors for microwave, terahertz, and far IR frequency ranges.

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We present the results of resonant photoemission spectroscopy experiments on Mo1−xRex alloy compositions spanning over two electronic topological transitions (ETTs) at critical concentrations xC1=0.05 and xC2=0.11. Photoelectrons show an additional resonance (R3) in constant initial state spectra of alloys along with two resonances (R1 and R2), which are similar to those observed in molybdenum. All the resonances show Fano-like line shapes. Asymmetry parameter q of resonances R1 and R3 of alloys is observed to be large and negative. Our analysis suggests that the origin of large negative q is associated with phonon assisted interband scattering between Mo-like states and the narrow band that appeared due to ETT.

We report systematic field-cooled (FC) magnetisation of superconducting (V$_{0.6}$Ti$_{0.4}$)-Y alloys in the presence of applied magnetic fields up to 7~T. A paramagnetic response is clearly observed just below the superconducting transition temperature ($T_{c}$) in low fields ($\leq 0.2$~T). The lower $T_{c}$ of the Y-rich precipitates, as compared to the bulk, is the origin of flux compression that leads to this paramagnetic response in low fields. It is also observed that the magnetisation obtained during field-cooled (FC) cooling cycle is lower than that of FC warming for the (V$_{0.6}$Ti$_{0.4}$)-Y alloys in fields higher than 0.02~T. Moreover, paramagnetic relaxation of the FC moment is also observed in this system. We infer that these features of the Y containing alloys are related to high field paramagnetic Meissner effect (HFPME). Our analysis shows that the large difference in pinning strength of the different pinning centres generated due to Y addition in the V$_{0.6}$Ti$_{0.4}$ alloys, is responsible for the HFPME. We find additional evidence of our claim in the form of extension of range of the temperature and magnetic fields over which the HFPME is observed, when the samples are subjected to cold work. The observation of HFPME up to 7~T has not been reported till now in any low $T_{c}$ superconductor, and only a very few high $T_{c}$ superconductors show HFPME upto such high fields.

β-Ag2Se is a promising material for room temperature thermoelectric applications and magneto-resistive sensors. However, no attention was paid earlier to the hysteresis in the temperature dependence of resistivity [ρ(T)]. Here, we show that a broad hysteresis above 35 K is observed not only in ρ(T), but also in other electronic properties such as Hall coefficient [RH(T)], Seebeck coefficient, thermal conductivity, and ultraviolet photoelectron spectra (UPS). We also show that the hysteresis is not associated with a structural transition. The ρ(T) and RH(T) show that β-Ag2Se is semiconducting above 300 K, but metallicity is retained below 300 K. While electronic states are absent in the energy range from the Fermi level (EF) to 0.4 eV below the EF at 300 K, a distinct Fermi edge is observed in the UPS at 15 K suggesting that the β-Ag2Se undergoes an electronic topological transition from a high-temperature semiconducting state to a low-temperature metallic state. Our study reveals that a constant and moderately high thermoelectric figure of merit in the range 300–395 K is observed due to the broad semiconductor to metal transition in β-Ag2Se.