Irradiation effects in high-entropy alloys and their applications

Abstract High-entropy alloy (HEA) superconductors—a new class of functional materials—can be utilized stably under extreme conditions, such as in space environments, owing to their high mechanical hardness and excellent irradiation tolerance. However, the feasibility of practical applications of HEA superconductors has not yet been demonstrated because the critical current density ( J c ) for HEA superconductors has not yet been adequately characterized. Here, we report the fabrication of high-quality superconducting (SC) thin films of Ta–Nb–Hf–Zr–Ti HEAs via a pulsed laser deposition. The thin films exhibit a large J c of &gt;1 MA cm −2 at 4.2 K and are therefore favorable for SC devices as well as large-scale applications. In addition, they show extremely robust superconductivity to irradiation-induced disorder controlled by the dose of Kr-ion irradiation. The superconductivity of the HEA films is more than 1000 times more resistant to displacement damage than that of other promising superconductors with technological applications, such as MgB 2 , Nb 3 Sn, Fe-based superconductors, and high- T c cuprate superconductors. These results demonstrate that HEA superconductors have considerable potential for use under extreme conditions, such as in aerospace applications, nuclear fusion reactors, and high-field SC magnets. 

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High critical current density and high-tolerance superconductivity in high-entropy alloy thin films

We have found an experimental evidence for the existence of the Dirac nodal line in the quasiparticle spectrum of the polar phase of superfluid $^3$He. The polar phase is stabilized by confinement of $^3$He between nm-sized cylinders. The temperature dependence of the gap, measured via frequency shift in the NMR spectrum, follows expected $\propto T^3$ dependence. The results support the Fomin extension of the Anderson theorem to the polar phase with columnar defects: perfect columnar non-magnetic defects do no perturb the magnitude of the gap in the polar phase. The existence of the node line opens possibilities to study Bogoliubov Fermi surfaces and flat-band fermions in the polar phase.

Topological nodal line in superfluid $^3$He and the Anderson theorem

Superconductivity and hardness of the equiatomic high-entropy alloy HfMoNbTiZr

Thixotropic deformation behavior, rapid spheroidization and solid-liquid homogenization of semi-solid Al0.8Co0.5Cr1.5CuFeNi HEA with multilevel microstructure

Influence of disorder strength on the superconducting mechanism of MgB2

We have developed a real-time dose monitoring system for a low-energy ion-beam facility. Before we developed the monitoring system, the system had given a substantial error of ±23% when we irradiated an ion beam with a dose as much as 3.0 × 1016 cm−2 on the Si substrate. Moreover, a low irradiation dose as small as 1013 cm−2 was scarcely able to be controlled because of a too short irradiation time of several seconds, producing a greater dose error. To develop a real-time dose monitoring system, in this work, we employed a current integrator in conjunction with a beam stopper, by which a dose of 3.0 ×1016 cm−2 can be exactly irradiated on the sample with less than ±6% error, which was ensured by the measurements of Rutherford backscattering spectroscopy.

Hye-ran Jeon

Papers

High critical current density and high-tolerance superconductivity in high-entropy alloy thin films

Influence of disorder strength on the superconducting mechanism of MgB2

Precision Control for Beam Irradiation Dose by Developing a Real-time Dose Monitoring System