Figure 2: Temperature- and field-dependent tunnelling spectroscopy curves and the superconducting energy gap of LTO films.
From: Anomalous magnetoresistance in the spinel superconductor LiTi2O4
(a) Normalized differential conductance versus bias voltage from 2 to 10.5 K (ΔT=0.5 K) in zero field. Experimental data are fitted with a modified BTK model with a constant broadening Γ term (red lines), and are vertically shifted above the 2 K curve for clarity. (b,c) Normalized differential conductance versus field from 0 to 9 T at 2 K, and from 0 to 7 T at 6 K (ΔB=1 T, B⊥ab plane). Experimental data (grey circles) are fitted with a modified BTK model with an increasing Γ as B is increased (red lines), and also with the two-channel model (cyan lines). Data in fields are vertically shifted. (d) Temperature-dependent energy gap values, Δ(T), are obtained from the BTK fits: 2Δ/kBTc=4 is obtained, indicating a medium-coupling BCS-like superconductor. (e) Normalized energy gap (Δ(B)/Δ(0T)) decreases as (B/Bc2)2 in the superconducting state, and can be scaled for different temperatures. In-field measurements were carried out at T=2, 6 and 10 K (open symbols extracted from modified BTK fittings with an increasing Γ and cross symbols from the two-channel model). (f) The normalized zero bias conductance (symbols) at 2 and 6 K shows a linear dependence on the magnetic field (red straight fitting line). The error bars in d–f represent the s.e. in the fit to the data.
