Dependence of the tunneling current I on the tip-sample distance zbetween PtIr tip and FeSe1– x Te x single crystal. The upper-right inset showsthe optical micrograph of the single crystal, while the lower left inset displays a histogram of the local work function (the barrier height).
STM topography of FeSe1– x Te x for 0.5 < x < 1. T = 4.9 K, I = 0.3 nA, V = –0.4 V.
Line profiles of the STM topography for FeSe0.3Te0.7 (a) and FeSe0.1Te0.9 (b). Dark spot ratio from STM versus Se content (1–x) from the electron-probe micro analyzer (EPMA) (c).
The STM topography, the dI/dV mapping, and the dI/dV line profiles for FeSe0.3Te0.7 at 4.9 K.
The dI/dV curves of FeSe0.5Te0.5 (a) at 4.2 K from break-junction tunneling spectroscopy (BJTS). The dI/dV fits using the broadened BCS density of states (dotted curves) (b) and (c).
Temperature evolution of dI/dV for FeSe0.5Te0.5. The conductance curves are shifted up for clarity.
The maximum gap structure observed in the measurements of FeSe1– x Te x (a). Peak-to-peak value of the superconducting gap 2Δ p–p versus Tc (K) for several superconductors 35,38,39 (b).
The dI/dV curves for FeSe0.5Te0.5 obtained from STS (A, B) and BJTS (C, D) at T = 4–5 K (a), and STS at 77 K (b).
Line profiles of dI/dV for FeSe0.5Te0.5 measured by STS at 4.9 K, showing the peak at −300 mV (a) and +100 mV (b). The profiles of (a) and (b) were taken from different samples.
Line profile of dI/dV from STS for FeS0.1Te0.9 at 4.9 K.
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