Superconducting proximity effect in epitaxial Al-InAs heterostructures

Abstract

Semiconductor-based Josephson junctions provide a platform for studying proximity effect due to the possibility of tuning junction properties by gate voltage and large-scale fabrication of complex Josephson circuits. Recently Josephson junctions using InAs weak link with epitaxial aluminum contact have improved the product of normal resistance and critical current, IcRN , in addition to fabrication process reliability. Here we study similar devices with epitaxial contact and find large supercurrent and substantial product of IcRN in our junctions. However we find a striking difference when we compare these samples with higher mobility samples in terms of product of excess current and normal resistance, IexRN . The excess current is negligible in lower mobility devices while it is substantial and independent of gate voltage and junction length in high mobility samples. This indicates that even though both sample types have epitaxial contacts only the high-mobility one has a high transparency interface. In the high mobility short junctions, we observe values of IcRN /∆ ∼ 2.2 and IexRN /∆ ∼ 1.5 in semiconductor weak links.

Electrical Control of Majorana Bound States Using Magnetic Stripes

“…Superconductivity is induced in the InAs NW by proximity to the Al half-covering. Although any semiconducting NW with high g-factor could be suitable, we consider InAs in which epitaxial growth and proximityinduced superconductivity have been demonstrated [54][55][56]. The NW is separated from the magnetic film by an insulator spacer (gray layer).…”

Phase Control of Majorana Bound States in a Topological X Junction

“…A push to seek alternative platforms for topological superconductivity led to the demonstration of robust proximityinduced superconductivity in a two-dimensional electron gas (2DEG) [18][19][20] which offers important opportunities to realize and control MBS [21][22][23][24][25][26][27]. Recent experiments in planar Josephson junctions (JJs) [28][29][30] reveal that topological superconductivity exists over a large parameter space without requiring fine tuning, while demonstrating the key role of superconducting phase to control the topological transition.…”

Tunable magnetic textures in spin valves: From spintronics to Majorana bound states

“…One of them employs the interplay between the superconducting and magnetic proximity effects to generate topological states in a two-dimensional electron gas (2DEG) [14,15]. It is further stimulated by the demonstrated robust proximity-induced superconductivity in all-epitaxial 2D structures and a versatile control of spin valves [16][17][18][19][20][21][22][23].…”

“…Recent experiments show a robust proximityinduced 2D superconductivity in InAs that forms transparent contacts with Al and yields a very large critical current in Josephson junctions [16,17]. With all-epitaxial growth, proximity-induced superconducting gap, ∆, attains nearly the bulk value of Al (∆ Al ∼ 0.2 meV) [17]. To strengthen the influence of tunable magnetic textures on 2DEG superconductivity and allow for a larger MNP-2DEG separation (l 0 , see Fig.…”