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.

Silver-assisted growth of high-quality InAs1- x Sb x nanowires by molecular-beam epitaxy.

InAs1-x Sb x nanowires show promise for use in nanoelectronics, infrared optoelectronics and topological quantum computation. Such applications require a high degree of growth control over the growth direction, crystal quality and morphology of the nanowires. Here, we report on the silver-assisted growth of InAs1-x Sb x nanowires by molecular-beam epitaxy for the first time. We find that the growth parameters including growth temperature, indium flux and substrate play an important role in nanowire growth. Relatively high growth temperatures and low indium fluxes can suppress the growth of non-[111]-oriented nanowires on Si (111) substrates. Vertically aligned InAs1-x Sb x nanowires with high aspect ratios can be achieved on GaAs (111)B substrates. Detailed structural studies suggest that high-quality InAs1-x Sb x nanowires can be obtained by increasing antimony content. Silver-indium alloy segregation is found in ternary alloy InAs1-x Sb x nanowires, and it plays a key role in morphological evolution of the nanowires. Our work provides useful insights into the controllable growth of high-quality III-V semiconductor nanowires.

Foreign-catalyst-free GaSb nanowires directly grown on cleaved Si substrates by molecular-beam epitaxy.

We have successfully fabricated foreign-catalyst-free GaSb nanowires directly on cleaved Si (111) substrates by molecular-beam epitaxy. We find that GaSb nanowires with the absence and presence of Ga droplets at the tip can be simultaneously obtained on cleaved Si substrates without Ga pre-deposition. Systematic morphological and structural studies verify that the two kinds of nanowires presented have different growth mechanisms, which are vapor-solid and vapor-liquid-solid mechanisms. The growth of GaSb nanowires can also be achieved on cleaved Si (110) and Si (100) substrates. The cleavage plane of the Si substrate has an obvious influence on the growth of the GaSb nanowires. The growth direction and crystal quality of catalyst-free nanowires are independent of the cleavage plane of the substrate. Our results may facilitate the understanding of the growth mechanism of III-V nanowires and the integration of foreign-catalyst-free GaSb nanowire-based devices with mature semiconductor technology.