Dynamics and mechanism of oxygen annealing in Fe1+yTe0.6Se0.4 single crystal

Abstract

Iron chalcogenide Fe(Te,Se) attracted much attention due to its simple structure, which is favorable for probing the superconducting mechanism. Its less toxic nature compared with iron arsenides is also advantageous for applications of iron-based superconductors. By intercalating spacer layers, superconducting transition temperature has been raised over 40 K. On the other hand, the presence of excess Fe is almost unavoidable in Fe(Te,Se) single crystals, which hinders the appearance of bulk superconductivity and causes strong controversies over its fundamental properties. Here we report a Systematical study of O2-annealing dynamics in Fe1+yTe1−xSex by controlling the amount of O2, annealing temperature, and time. Bulk superconductivity can be gradually induced by increasing the amount of O2 and annealing time at suitable temperatures. The optimally annealed crystals can be easily obtained by annealing with ~1.5% molar ratio of oxygen at 400°C for more than 1 hour. Superconductivity was witnessed to evolve mainly from the edge of the crystal to the central part. After the optimal annealing, the complete removal of excess Fe was demonstrated via STM measurements. Some fundamental properties were recharacterized and compared with those of as-grown crystals to discuss the influence of excess Fe.

Effects of heavy-ion irradiation on FeSe

“…5 (right axis), the self-field J c at 2 K is increased about 5 times from ∼4×10 4 A/cm 2 for the pristine crystal to ∼2×10 5 A/cm 2 for the crystals with B φ = 2 T. Such a large value of enhanced J c is already close to that reported in high-quality FeTe 1−x Se x single crystals [55,56]. For B φ > 2 T, the value of J c is gradually suppressed with the increase in columnar defects.…”

Multiband effects and possible Dirac fermions inFe1+yTe0.6Se0.4Sun1, Taen2, Yamada3 et al. 2014Phys. Rev. BSelf Cite628481View full textAdd to dashboardCite

“…Actually, no specific heat jump associated with superconducting transition can be observed in the as-grown crystal. 29 The filamentary superconductivity may come from some small parts of the crystal containing less amount of excess Fe, like the surface layers, which may have been slightly annealed at room temperature in the air. temperatures for the as-grown, half-annealed, and fullyannealed Fe 1+y Te 0.6 Se 0.4 single crystals, respectively.…”

“…Details of the sample preparing and the composition analysis have been reported in our previous publications. 29 Magnetization measurements were performed using a commercial SQUID magnetometer (MPMS-XL5, Quantum Design). The Hall resistivity ρ yx and magnetoresistance ρ xx were measured at the same time using the six-lead method with the applied field parallel to c-axis and perpendicular to the applied current.…”

Tuning electronic properties of FeSe0.5Te0.5 thin flakes using a solid ion conductor field-effect transistor

“…The non-metallic characteristic is caused by the localization effect from interstitial Fe [26,27]. After removing the interstitial Fe by annealing crystals in oxygen, we improved the quality and enhanced the T zero c to 14.2 K. In Fig.…”