Investigation of Transport Properties for FeSe_1−xTe_x Thin Films under Magnetic Fields

Abstract

We investigated the transport properties under magnetic fields of up to 9 T for FeSe 1−x Te x thin films on CaF 2 . Measurements of the temperature dependence of the electrical resistivity revealed that for x = 0.2-0.4, where T c is the highest, the width of the superconducting transition increased with increasing magnetic field, while the width was almost the same with increasing magnetic field for x = 0-0.1. In addition, the temperature dependence of the Hall coefficient drastically changed between x = 0.1 and 0.2 at low temperatures. These results indicate that clear differences in the nature of the superconductivity and electronic structure exist between x = 0-0.1 and x ≥ 0.2.

Control of structural transition in FeSe1−xTex thin films by changing substrate materials

“…We believe this fact is not due to the variation in the Te content12. Figure 1e shows the relation between the a -axis and the c -axis lengths in FeSe 1− x Te x films on LAO and CaF 2 81220. For the samples with the same Te content, the c -axis and the a -axis lengths show a weak negative correlation regardless of the substrate materials, which cannot be explained by a variation in Te content because it should result in a positive correlation.…”

“…1d, where the data for films on CaF 2 81220 are also plotted for comparison. The c -axis lengths of the films on LAO exhibit almost linear dependence on x including two end member materials, FeSe and FeTe21, as in the case of films on CaF 2 12.…”

“…2f and T * are plotted as a function of x in Fig. 3, where T c and T * for films on CaF 2 81220 (See the supporting information) and T c of bulk samples323 are also plotted for comparison. Additionally, we set an error bar for considering slight deviations of T * at each compositions in Fig.…”

Comparative Review on Thin Film Growth of Iron-Based Superconductors

“…Indeed, a recent ARPES measurement for strained FeSe films revealed that the nematicity weakens as the a-axis length of the films shrinks [208]. [131,132,209]) , respectively. In the inset, the dependence of T onset c on Te content x is shown.…”

“…Therefore, we believe that the sudden change in T c at x opt in Figure 3b is probably related to the structural/nematic transition since the Te content where T s disappears coincides x opt [133], and that the orthorhombic distortion and/or nematic order may not be favorable for the superconductivity in iron chalcogenides. At x opt , which is closely related to the structural/nematic transition, big changes are observed in some physical properties other than T c : the upper critical field, B c2 [209], the superconducting transition width [213], the ratio of B c2 along the ab-plane and the c-axis in the orbital limit, γ ≡ B //ab c2,0K /B //c c2,0K [213], the temperature dependence of Hall coefficient, R H (T) [209], and the optical conductivity [214]. In Figure 5c-f, we plot the magnetic field dependence of magneto resistance, MR, at different temperatures, which is the so-called Kohler plot, where the MR can be scaled by ρ(H, T)/ρ(H = 0, T) = F(ω c τ) = F(µ 0 H/ρ(H = 0, T)) according to the Kohler's rule.…”