Suppressing Andreev Bound State Zero Bias Peaks Using a Strongly Dissipative Lead

Hybrid semiconductor-superconductor nanowires are predicted to host Majorana zero modes that induce zero-bias peaks (ZBPs) in tunneling conductance. ZBPs alone, however, are not sufficient evidence due to the ubiquitous presence of Andreev bound states. Here, we implement a strongly resistive normal lead in InAs-Al nanowire devices and show that most of the expected Andreev bound state–induced ZBPs can be suppressed, a phenomenon known as environmental Coulomb blockade. Our result is the first experimental demonstration of this dissipative interaction effect on Andreev bound states and can serve as a possible filter to narrow down the ZBP phase diagram in future Majorana searches.

Figure 1

(a) False-color SEM image of Device A. Thickness of the dissipative resistor (red), contact or gate (yellow), and InAs (diameter) are labeled. The substrate is p-doped Si covered by 300 nm thick ${\mathrm{SiO}}_2$, acting as a global back gate. (b) $G(V,T)$ of device A at different $T$s. $B_{\perp }=1\mathrm{T}$. (c) Replotting (b) using dimensionless units. Inset: $T$ dependence of the zero-bias $G$. (d) and (e) are for Devices B and C with different dissipative resistors.

Figure 2

(a)–(f) For Device A. (a) $V_{\mathrm{TG}}$ scan of a singlet ABS at $B=0\mathrm{T}$. (b),(c) $B$ scans of the ABS from (a) ($V_{\mathrm{TG}}$ labeled). (d) $V_{\mathrm{TG}}$ scan of another ABS at $B=0\mathrm{T}$ with singlet (S) and doublet (D) regions labeled. (e),(f) $B$ scans of the singlet and doublet ABSs. (g),(h) Gate and $B$ scans of an ABS in Device X (without dissipation). (i) Black and red curves are line cuts from (b)–(e) and (g),(h), respectively (see corresponding arrows). $B$ is aligned with the nanowire axis. $T\sim 20\mathrm{mK}$.

Figure 3

(a) Upper, gate scan of an ABS at 0.3 T. $T\sim 20\mathrm{mK}$. Lower, extracted power-law exponents from $T$ dependence in units of $r$. (b) $T$ dependence (colored dots) of a line cut in (a). The solid lines are theory simulations. (c) $T$ dependence of the zero-bias $G$ from (a) at three $V_{\mathrm{TG}}$s, labeled in the lower panel (a). Dashed lines are the power-law fits. (d) $T$ dependence of the normalized zero-bias $G$ from (b) for Device A (black dots) and Device X (red dots), together with thermal simulations (solid lines). (e) $T$ dependence of a ZBP [from Fig. 2] in Device X (dots) and thermal simulations (lines).

Figure 4

(a) Zero-bias $G$ at 1 T (aligned with the nanowire) versus $V_{\mathrm{BG}}$ and $V_{\mathrm{TG}}$. (b) $G$ versus $V_{\mathrm{TG}}$ and $V$. Lower panel zero-bias line cut, corresponding to the orange dashed line in (a). (c) Vertical line cuts from (b); see colored dashed lines, resolving no ZBPs. $T\sim 20\mathrm{mK}$.