Basic scientific questions and tantalizingly revolutionary applications have been intertwined throughout the 100-year history of superconductivity. Within two years of his discovery of superconductivity in 1911, H. Kamerlingh Onnes imagined high-field applications for superconducting wires, only to have his hopes dashed by limitations of upper critical field and critical current density. Over the next 98 years, a scientific tango would play out repeatedly between (1) discovering and understanding new superconductors, often with higher transition temperature values and (2) improving these materials’ upper critical field and critical current values while keeping manufacturing costs down. In this article, we take stock of where the field currently stands, with mature, developing, and recently discovered superconductors, and try to give a sense of where it may be going.

The microstructures of Zr70Cu30 and Zr70Ni30 metallic glasses (MGs) were investigated via the synchrotron radiation techniques combined with the reverse Monte-Carlo simulations. Although Cu and Ni are neighbor elements in the periodic table and their atomic radii are almost the same in length, it is found that atomic- and cluster-scale structural differences occur between these two Zr-based MGs. In particular, the relatively regular clusters caused by the narrow distributions of atomic separations and bond angles are detected in Zr70Cu30. This is the structural origin of the different glass-forming abilities in ZrCu and ZrNi alloys. This work has implications for understanding of the glass-forming mechanism in this class of glassy materials.

Variably spaced semiconductor superlattices (VSSLs) exhibited superior electron mobility and rectification because of electronic level alignment. We investigated the thermoelectric properties of VSSL structures using a self-consistent nonequilibrium Green’s function quantum model to capture the ballistic electron transport and anatomistic nonequilibrium Green’s function model to capture the phonon transport. A figure of merit was calculated as a function of temperature for two VSSL strain silicon–germanium materials and a non-VSSL material. Calculation of the figure of merit (ZT) versus temperature for a VSSL demonstrated a 17 times increase in power factor at the expense of a 4 times increase in thermal conductivity at room temperature compared to a comparable uniform superlattice. Calculation determined a ZT of 0.20 for a VSSL compared to a ZT of 0.04 for non-VSSL material at 400 K. VSSLs proved to be a candidate material to further increased ZT near room temperature for superlattice materials.

The size dependence of the lattice parameter of nanosolids has extensively been studied because lattice strain engineering is important in controlling the physical properties of nanowires (NWs), such as band gap, carrier transport, mechanical strength, etc. We have investigated the size-dependent lattice behavior of microstructure-controlled Sn NWs with radii of 7–35 nm. The NW microstructures were controlled as single-crystal, granular, and bamboo structures in the longitudinal direction. Results showed that the a-axis lattice parameter in the [100]-longitudinal direction of NWs can be controlled within 1% by varying the wire microstructure for the same wire radius because it is strongly dependent on the microstructure and the wire radius. Moreover, as the randomness of the grain orientation in the microstructure-controlled NWs increases, by which the anisotropy of surface stress is effectively reduced, the lattice strain of the NW can be compressive or tensile as a function of the wire radius. The longitudinal lattice parameters of microstructure-controlled Sn NWs can be tailored by reducing the effective anisotropy of surface stresses under a dimension confinement in the nanometer scale.

In- and Yb-doped CoSb3 thin films were prepared by pulsed laser deposition. Process optimization studies revealed that a very narrow process window exists for the growth of single-phase skutterudite films. The electrical conductivity and Seebeck coefficient measured in the temperature range 300–700 K revealed an irreversible change on the first heating cycle in argon ambient, which is attributed to the enhanced surface roughness of the films or trace secondary phases. A power factor of 0.68 W m−1 K−1 was obtained at ∼700 K, which is nearly six times lower than that of bulk samples. This difference is attributed to grain boundary scattering that causes a drop in film conductivity.