Achieving the depairing limit along the c axis in Fe1+yTe1−xSe

Abstract

We report the achieving of depairing current limit along c-axis in Fe1+yTe1−xSex single crystals. A series of crystals with Tc ranging from 8.6 K to 13.7 K (different amount of excess Fe, y) were fabricated into c-axis bridges with a square-micrometer cross-section. The critical current density, Jc, was directly estimated from the transport current-voltage measurements. The transport Jc reaches a very large value, which is about one order of magnitude larger than the depinning Jc, but comparable to the calculated depairing Jc ∼ 2 × 10 6 A/cm 2 at 0 K, based on the Ginzburg-Landau (GL) theory. The temperature dependence of the depairing Jc follows the GL-theory (∝ (1-T /Tc) 3/2 ) down to ∼ 0.83 Tc, then increases with a reduced slope at low temperatures, which can be qualitatively described by the Kupriyanov-Lukichev theory. Our study provides a new route to understand the behavior of depairing Jc in iron-based superconductors in a wide temperature range. * sunyue@phys.aoyama.ac.jp † hkitano@phys.aoyama.ac.jp

Supercurrent-induced topological phase transitions

“…Using a sample narrower than the Pearl length Λ, the current distributes almost uniformly in the sample. Although the Pearl length is the order of 0.1-1 µm, it is possible to make a sample smaller than the length scale thanks to the development of the nanopatterning techniques for superconductors [79][80][81]. Indeed, in experiments for cuprate superconductors [79] and ironbased superconductors [80,81], this type of sample is realized and the results support the spatially uniform current.…”

“…Although the Pearl length is the order of 0.1-1 µm, it is possible to make a sample smaller than the length scale thanks to the development of the nanopatterning techniques for superconductors [79][80][81]. Indeed, in experiments for cuprate superconductors [79] and ironbased superconductors [80,81], this type of sample is realized and the results support the spatially uniform current. Another way is to see the center region of samples, narrow but broader than the Pearl length [37].…”

“…This is because the vortex flow induces a dissipative current, and j c typically becomes very small. Indeed, such samples avoiding vortices are used in experiments, and the large critical current, called depairing current [34], is observed [79][80][81]. However, even if we avoid the above difficulty, there are still problems.…”

Supercurrent-Induced Weyl Superconductivity

“…In the above candidate superconductors, the London penetration depth 𝜆 or the Pearl length Λ = 2𝜆 2 /𝑑 (𝑑: the sample thickness) are estimated to 0.1-1µm [108][109][110]. Recent developments in nanopatterning techniques for superconductors [111][112][113] would enable us to make a sample smaller than the length scales.…”

Comparative study of superconducting and normal-state anisotropy in Fe$_{1+y}$Te$_{0.6}$Se$_{0.4}$ superconductors with controlled amounts of interstitial excess Fe

“…The bridges in the ab plane and along the c axis used for the measurements of normal state anisotropy, as shown schematically in the insets of Figs. 3(a) and 3(b), were fabricated by using the focused ion beam (FIB) technique [47][48][49].…”