Fig. 3: Surface topography and the superconducting gap with variable temperatures and fields.
From: Intrinsic surface p-wave superconductivity in layered AuSn4
a High-resolution image reveals a superstructure with the modulation of wavy troughs, the image size is 40 × 40 nm2. The bright spots on the surface can be attributed to the residual Sn from the cleavage. b Zoom-in atomic resolution image shows a square-net lattice and \(\sqrt{2}\times 2\sqrt{2}\) superstructure with the unit cell size of (6.3~6.6) Å × (11.6~12.23) Å (6.6 Å × 13.2 Å in theory) for surface Sn lattice. c A representative dI/dV spectrum taken at 0.16 K, showing a superconducting gap with the size and depth of gap ~0.487 meV and 87%, respectively. Here, we adopt small lock-in modulation bias (Vmod) ~ 40 μV in order to eliminate the broadening effect. d A series of normalized dI/dV spectra with perpendicular fields varying from 0 Oe to 500 Oe (left) and temperatures from 0.38 K to 2.5 K (right), respectively. Set points: Vb = 10 mV, It = 400 pA, the Vmod is 0.3 mV. Note, the STS taken at 0.38 K with 0.3 mV Vmod, give a dual-gap feature with enlarged gap size and shallower depth, probably due to the thermal broadening effect and large lock-in modulation bias. e Temperature (upper) and field (lower) dependences of normalized ZBC extracted from panel d. The deduced Tc and Hc are 2.64 K and 660 Oe, respectively. f The gap evolution with temperatures above Tc.
