Epitaxial semiconductor–superconductor hybrid materials are an excellent basis for studying mesoscopic and topological superconductivity, as the semiconductor inherits a hard superconducting gap while retaining tunable carrier density1. Here, we investigate double-quantum-dot structures made from InAs nanowires with a patterned epitaxial Al two-facet shell2 that proximitizes two gate-defined segments along the nanowire. We follow the evolution of mesoscopic superconductivity and charging energy in this system as a function of magnetic field and voltage-tuned barriers. Interdot coupling is varied from strong to weak using side gates, and the ground state is varied between normal, superconducting and topological regimes by applying a magnetic field. We identify the topological transition by tracking the spacing between successive co-tunnelling peaks as a function of axial magnetic field3 and show that the individual dots host weakly hybridized Majorana modes.
At a glance
- Hard gap in epitaxial semiconductor–superconductor nanowires. Nat. Nanotech. 10, 232–236 (2015). et al.
- Epitaxy of semiconductor–superconductor nanowires. Nat. Mater. 14, 400–406 (2015). et al.
- Exponential protection of zero modes in Majorana islands. Nature 531, 206–209 (2016). et al.
- Helical liquids and Majorana bound states in quantum wires. Phys. Rev. Lett. 105, 177002 (2010). , &
- Majorana fermions and a topological phase transition in semiconductor–superconductor heterostructures. Phys. Rev. Lett. 105, 077001 (2010). , &
- Milestones toward Majorana-based quantum computing. Phys. Rev. X 6, 031016 (2015). et al.
- Topological quantum computation. Bull. Am. Math. Soc. 40, 31–38 (2003). , , &
- Non-Abelian anyons and topological quantum computation. Rev. Mod. Phys. 80, 1083–1159 (2008). , , , &
- Signatures of Majorana fermions in hybrid superconductor–semiconductor nanowire devices. Science 336, 1003–1007 (2012). et al.
- Anomalous zero-bias conductance peak in a Nb–InSb nanowire–Nb hybrid device. Nano Lett. 12, 6414–6419 (2012). et al.
- Zero-bias peaks and splitting in an Al–InAs nanowire topological superconductor as a signature of Majorana fermions. Nat. Phys. 8, 887–895 (2012). et al.
- Superconductor–nanowire devices from tunneling to the multichannel regime: zero-bias oscillations and magnetoconductance crossover. Phys. Rev. B 87, 241401 (2013). et al.
- Observation of Majorana fermions in ferromagnetic atomic chains on a superconductor. Science 346, 602–607 (2014). et al.
- Tunable double quantum dots in InAs nanowires defined by local gate electrodes. Nano Lett. 5, 1487–1490 (2005). , , &
- Electron transport through double quantum dots. Rev. Mod. Phys. 75, 1–22 (2002). et al.
- Experimental evidence for parity-based 2e periodicity in a superconducting single-electron tunneling transistor. Phys. Rev. Lett. 69, 1997–2000 (1992). , , &
- Resonant Cooper pair tunneling through a double-island qubit. Phys. Rev. Lett. 88, 017003 (2002). , &
- Parity lifetime of bound states in a proximitized semiconductor nanowire. Nat. Phys. 11, 1017–1021 (2015). et al.
- Single-electron charging in double and triple quantum dots with tunable coupling. Phys. Rev. Lett 75, 705–708 (1995). et al.
- 1997). et al. Electron Transport in Quantum Dots (Kluwer Academic,
- The Coulomb blockade in coupled quantum dots. Science 274, 1332–1335 (1996). , , , &
- A Ge/Si heterostructure nanowire-based double quantum dot with integrated charge sensor. Nat. Nanotech. 2, 622–625 (2007). et al.
- Measuring interactions between tunnel-coupled quantum dots. Phys. Rev. B 53, 1423–1420 (1996). et al.
- A semiconductor nanowire-based superconducting qubit. Phys. Rev. Lett. 115, 127001 (2015). et al.
- Hybrid superconductor–quantum dot devices. Nat. Nanotech. 5, 703–711 (2010). , , &
- Two-electron quantization of the charge on a superconductor. Nature 365, 422–424 (1993). , , , &
- Weak charge quantization on a superconducting island. Phys. Rev. B 66, 054502 (2002). , , &
- Measurement of the even–odd free-energy difference of an isolated superconductor. Phys. Rev. Lett. 70, 994–997 (1993). , , , &
- Single-electron charging of a superconducting island. Phys. Rev. Lett. 69, 1993–1996 (1992). &
- Conductance of a proximitized nanowire in the Coulomb blockade regime. Phys. Rev. B 93, 235431 (2016). , &
- Splitting of the zero-bias conductance peak as smoking gun evidence for the existence of the Majorana mode in a superconductor–semiconductor nanowire. Phys. Rev. B 86, 220506 (2012). , &
- Unpaired Majorana fermions in quantum wires. Phys. Usp. 44, 131–136 (2001).
- Towards a realistic transport modeling in a superconducting nanowire with Majorana fermions. Phys. Rev. B 87, 024515 (2013). , , & et al.
- Dimensional crossover in spin–orbit-coupled semiconductor nanowires with induced superconducting pairing. Phys. Rev. B 87, 094518 (2013). , &