Hybrid quantum dot devices in magic-angle twisted bilayer graphene
ORAL
Abstract
We introduce magic-angle twisted bilayer graphene (MATBG) as a novel material platform hosting semiconductor-superconductor hybrid quantum dot devices.
We demonstrate carrier confinement through Coulomb blockade in combination with superconductivity and study transport in two distinct regimes: a superconducting island and a quantum dot Josephson junction (S-QD-S).
In the superconducting island regime, we observe the parity effect with a complete 2e to e crossover of the carrier charge as a function of magnetic field. In the S-QD-S regime, we observe an even-odd modulation of the Andreev bound state spectrum, compatible with the formation of the Yu-Shiba-Rusinov states.
Our work exploits the tunability of MATBG quantum devices [1,2,3] to realize quantum dot hybrid systems built on the interface between different collective electronic phases [4,5] in this material.
[1] de Vries, F.K., et al. Gate-defined Josephson junctions in magic-angle twisted bilayer graphene. Nat. Nanotechnol. 16, 760–763 (2021).
[2] Rodan-Legrain, et al. Highly tunable junctions and non-local Josephson effect in magic-angle graphene tunnelling devices. Nat. Nanotechnol. 16, 769–775 (2021).
[3] Rothstein, A., et al. Gate-defined flat-band charge carrier confinement in twisted bilayer graphene. Nano Letters 25 (16), 6429-6437 (2025).
[4] Cao, Y., et al. Unconventional superconductivity in magic-angle graphene superlattices. Nature 556, 43–50 (2018).
[5] Lu, X., Superconductors, orbital magnets and correlated states in magic-angle bilayer graphene. Nature 574, 653–657 (2019).
We demonstrate carrier confinement through Coulomb blockade in combination with superconductivity and study transport in two distinct regimes: a superconducting island and a quantum dot Josephson junction (S-QD-S).
In the superconducting island regime, we observe the parity effect with a complete 2e to e crossover of the carrier charge as a function of magnetic field. In the S-QD-S regime, we observe an even-odd modulation of the Andreev bound state spectrum, compatible with the formation of the Yu-Shiba-Rusinov states.
Our work exploits the tunability of MATBG quantum devices [1,2,3] to realize quantum dot hybrid systems built on the interface between different collective electronic phases [4,5] in this material.
[1] de Vries, F.K., et al. Gate-defined Josephson junctions in magic-angle twisted bilayer graphene. Nat. Nanotechnol. 16, 760–763 (2021).
[2] Rodan-Legrain, et al. Highly tunable junctions and non-local Josephson effect in magic-angle graphene tunnelling devices. Nat. Nanotechnol. 16, 769–775 (2021).
[3] Rothstein, A., et al. Gate-defined flat-band charge carrier confinement in twisted bilayer graphene. Nano Letters 25 (16), 6429-6437 (2025).
[4] Cao, Y., et al. Unconventional superconductivity in magic-angle graphene superlattices. Nature 556, 43–50 (2018).
[5] Lu, X., Superconductors, orbital magnets and correlated states in magic-angle bilayer graphene. Nature 574, 653–657 (2019).
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Presenters
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Alexandra Mestre-Torà
- ETH Zurich