Universal Conductance Scaling of Andreev Reflections Using a Dissipative Probe

The Majorana search is caught up in an extensive debate about the false-positive signals from nontopological Andreev bound states. We introduce a remedy using the dissipative probe to generate electron-boson interaction. We theoretically show that the interaction-induced renormalization leads to significantly distinct universal zero-bias conductance behaviors, i.e., distinct characteristic power law in temperature, for different types of Andreev reflections, that show a sharp contrast to that of a Majorana zero mode. Various specific cases have been studied, including the cases in which two charges involved in an Andreev reflection process maintain or lose coherence, and the cases for multiple Andreev bound states with or without a Majorana. A transparent list of conductance features in each case is provided to help distinguish the observed subgap states in experiments, which also promotes the identification of Majorana zero modes.

Figure 1

Illustration of the system setup. The inset is the equivalent circuit. A bias voltage $V_{\mathrm{bias}}$ is applied on the lead.

Figure 2

(a) All possible processes. (b) Leading process after RG. (c) Incoherent dissipative Andreev reflection via a cluster of ABSs.

Figure 3

Scaling dimension and amplitude (inset) of the operator $\propto t_{h\downarrow }$, when $t_{e\uparrow }$ is dominating. Temperature decreases when value of $x$ axis increases. (a) When $r=0.1$, $t_{h\downarrow }$ becomes RG irrelevant when $T\approx 0.05T_0$, with the peak height $\approx 0.7$. (b) When $r=0.45$, the ABS conductance arrives at its peak position much faster $T\approx 0.11T_0$, with a much smaller peak height $\approx 0.24$. Other parameters in (a) and (b) are the same.