Parity transitions in the superconducting ground state of hybrid InSb-Al Coulomb islands

Jie Shen, Sebastian Heedt, Francesco Borsoi, Bernard van Heck, Sasa Gazibegovic, Roy L.M. Op Het Veld, Diana Car, Senja J.J. Ramakers, Guanzhong Wang, Di Xu, Daniël Bouman, Attila Geresdi, Erik P.A.M. Bakkers, Leo P. Kouwenhoven

Research output: Contribution to journalArticleScientificpeer-review

18 Citations (Scopus)
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The number of electrons in small metallic or semiconducting islands is quantised. When tunnelling is enabled via opaque barriers this number can change by an integer. In superconductors the addition is in units of two electron charges (2e), reflecting that the Cooper pair condensate must have an even parity. This ground state (GS) is foundational for all superconducting qubit devices. Here, we study a hybrid superconducting-semiconducting island and find three typical GS evolutions in a parallel magnetic field: a robust 2e-periodic even-parity GS, a transition to a 2e-periodic odd-parity GS, and a transition from a 2e- to a 1e-periodic GS. The 2e-periodic odd-parity GS persistent in gate-voltage occurs when a spin-resolved subgap state crosses zero energy. For our 1e-periodic GSs we explicitly show the origin being a single zero-energy state gapped from the continuum, i.e., compatible with an Andreev bound states stabilized at zero energy or the presence of Majorana zero modes.

Original languageEnglish
Number of pages8
JournalNature Communications
Issue number1
Publication statusPublished - 2018

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