Figure 1

PCAR spectra for different contact resistances at $T$ ∼ 0.35 K: (a) $I\parallel b$ and (b) $I\perp b$. Solid lines (red) are fits to the modified two-gap BTK model. The corresponding fits with a single-gap model (black dashed lines) are also shown for comparison for some of the spectra. (c) and (d) Scatter plots of a superconducting energy gap obtained by fitting the modified BTK model to the experimental PCAR spectra for $I\parallel b$ and $I\perp b$ plotted as a function of the serial number of the spectra. The bands are guides to the eye. (e) and (f) Temperature dependence of the PCAR spectra for two low $R_c$ contacts for $I\parallel b$ and $I\perp b$, respectively.Reuse & Permissions

Figure 2

Comparison between one-gap and two-gap fits for PCAR spectra recorded at the lowest temperature for (a) $I\parallel b$ and (d) $I\perp b$. Temperature variation in the PCAR spectra for (b) $I\parallel b$ and (e) $I\perp b$. (c) and (f) show the temperature dependence of the superconducting energy gaps extracted from (b) and (e), respectively; the solid black lines are the expected BCS variation in Δ. (g) and (h) show the temperature variation in the broadening parameters and the barrier parameters obtained from the best fits of the spectra in (b) and (e), respectively. (i) Temperature variation in the relative weight factor ($w$) for the two gaps used in the best fit of the spectra in (b) and (e). The blue solid line in panel (c) shows the real part of the ac susceptibility (χ) as a function of temperature showing the superconducting transition of BiPd.Reuse & Permissions

Figure 3

Magnetic-field dependence of PCAR spectra showing the ZBCP for two point contacts with (a) $I\parallel b$ and (b) $I\perp b$. The spectra are measured at 0.4 K.Reuse & Permissions

Figure 4

(a) Height of the ZBCP measured at 0.4 K as function of contact diameter $d$. The solid triangles (red) correspond to $I\parallel b$, and the open triangles correspond to $I\perp b$. The thick shaded lines are guides to the eye. It shows two branches of points associated with the ABS in two different directions. (b) $H_c$${}_2$ as a function of temperature ($T$) for $H\parallel b$ and $H\perp b$. The inset shows ac susceptibility as a function of the magnetic field at $T$ = 0.4 K. The $H_c$${}_2$ (shown by arrows) has been extracted from susceptibility data taken as a function of the magnetic field at different temperatures.Reuse & Permissions

Figure 5

(a) Schematic of the spin-split Fermi surface due to spin-orbit coupling, forming the + (outer surface) and − (inner surface) helicity bands. The spin eigenstates (shown by arrows) point parallel and antiparallel to $\mathit{g}$($\mathit{k}$), respectively. (b) and (c) One possible realization of the gap functions corresponding to ${\Delta }_{-}$ and ${\Delta }_{+}$ corresponding to a particular choice of the vector $\mathit{g}$($\mathit{k}$). Darker (red) and lighter (blue) regions correspond to positive and negative values of the gap function, respectively. Note that the small monoclinic distortion of BiPd has been neglected in the symmetry of the gap functions.Reuse & Permissions