Evolution of superconducting and transport properties in annealed FeTe_1−xSe_x(0.1 ≤x≤ 0.4) multiband superconductors

Abstract

We investigated the superconducting and transport properties in FeTe 1−x Se x (0.1 ≤ x ≤ 0.4) single crystals prepared by O 2 -annealing. Sharp superconducting transition width observed in magnetization measurement and the small residual resistivity prove the high quality of the crystals. All the crystals manifest large, homogeneous, and isotropic critical current density J c with self-field value over 10 5 A/cm 2 at 2 K. The large and field-robust critical current densities prove that the superconductivity in FeTe 1−x Se x (0.1 ≤ x ≤ 0.4) is in bulk nature. The values of anisotropy parameter close to T c for crystals with different Se doping levels all reside in the range of 2 -3. Hall coefficients R H keeps positive and almost constant value at high temperatures, followed by a sudden decreases before reaching T c , which indicates that the electron-type charge carriers become dominant at low temperatures. Furthermore, the characteristic temperature for the sudden decrease in R H gradually increases with Se doping. arXiv:1502.04284v1 [cond-mat.supr-con]

Thermal evolution of antiferromagnetic correlations and tetrahedral bond angles in superconductingFeTe1−xSex

“…This is consistent with nuclear magnetic resonance results for an x = 0.5 sample in which the quantity 1/T 1 T , where 1/T 1 is the spinlattice relaxation rate measured at the Te site, decreases as the temperature is reduced [83]. This loss of magnetic susceptibility is correlated with a growth in electronic conductivity [42,84] and a crossover from incoherence to coherence. This correlation parallels the more extreme changes observed in Fe 1+y Te [57,85].…”

Influence of interstitial Fe to the phase diagram of Fe1+yTe1−xSex single crystals

“…Besides, all the annealed crystals show relatively sharp SC transition width Δ T c  ≤ 1 K. The SC observed in the annealed crystals has already been proved to be in bulk nature by the clear specific heat jump and a large value of critical current density, J c , in our previous report33. Actually, when the Se doping level is equal or larger than 0.05, all the annealed crystals show large value of J c  ~ 3 × 10 5  A/cm 2 at 2 K under self-field similar to that reported for the crystal with x  = 0.433738.…”

“…In addition, Se/Te ratio is found to change little after annealing (≤1%). The energy dispersive x-ray spectroscopy (EDX) measurements show that Te and Se are almost homogeneously distributed in both the as-grown and annealed crystals38. The amount of interstitial Fe in the as-grown crystals is estimated as ~10–14% based on the ICP results.…”

Achieving the depairing limit along the c axis in Fe1+yTe1−xSeSun1, Ohnuma2, Ayukawa3 et al. 2020Phys. Rev. BSelf Cite170110View full textAdd to dashboardCite

“…In the crystal with T c = 13.7 K (see Fig. 2(f)), J c reaches a very large value ∼ 1.3 × 10 6 A/cm 2 at 4 K. This value of the transport J c is about one order of magnitude larger than the depinning J c (∼ 1.3 × 10 5 A/cm 2 at 4 K), which has been estimated from the MHLs for both H c and H ab [50,51]. On the other hand, the depairing J c along c-axis given in the GL-theory by J GL dp = cφ 0 /12 √ 3π 2 ξ c λ 2 c is estimated as ∼ 2×10 6 A/cm 2 using the coherence length ξ c (0 K) 3.0 nm [33], and penetration depth λ c (0 K) 1.32 µm [32].…”

“…Note that J c of the crystal with minimum T c is still larger than the depinning J c estimated from MHLs (See the open symbol in Fig. 4) [50,51]. It indicates that the depairing current limit is achieved in all the samples.…”