Andreev bound states and tunneling characteristics of a noncentrosymmetric superconductor

The tunneling characteristics of planar junctions between a normal metal and a noncentrosymmetric superconductor such as $\mathrm{Ce}{\mathrm{Pt}}_3\mathrm{Si}$ are examined. It is shown that the superconducting phase with mixed parity can give rise to characteristic zero-bias anomalies in certain junction directions. Andreev bound states at the interface are the origin of these zero-bias anomalies. The tunneling characteristics for different directions allow us to test the structure of the parity-mixed pairing state.

Figure 1

(Color online) Normalized low-temperature conductance $G\left(\mathit{eV}\right)$ for a normal metal/noncentrosymmetric superconductor junction with boundary orientation $\mathbf{n}\Vert \mathbf{z}$. The ratio $q$ of the gap amplitudes is varied from 0 to 1.5 in steps of 0.1. Between two subsequent curves, a vertical offset of 0.2 has been used for clarity of the plot. The transparency of the interface is set to $D_0=0.1$.

Figure 2

(Color online) Typical angular resolved density of states $N(E,\widehat{\mathbf{k}})$ at the boundary of a noncentrosymmetric superconductor with normal vector $\mathbf{n}\Vert \mathbf{y}$. For this example, we set $q=0.5$ and $\theta =\pi ∕2$, i.e., we deal with $\widehat{\mathbf{k}}$ vectors of the $x,y$ plane only. Bright colors represent high spectral weight. The branches of low-energy Andreev bound states according to Eq. (14) are clearly visible.

Figure 3

(Color online) Normalized low-temperature conductance $G\left(\mathit{eV}\right)$ for a normal metal/noncentrosymmetric superconductor junction with boundary orientation $\mathbf{n}\perp \mathbf{z}$. The ratio $q$ of the gap amplitudes is varied from 0 to 1.5 in steps of 0.1. Between two subsequent curves, a vertical offset of 0.2 has been used for clarity of the plot. The transparency of the interface is set to $D_0=0.1$.