Tunable valley splitting and bipolar operation in graphene quantum dots

Chuyao Tong, Rebekka Garreis, Angelika Knothe, Marius Eich , Agnese Sacchi, Kenji Watanabe, Takashi Taniguchi, Vladimir Fal'ko, Thomas Ihn, Klaus Ensslin, Annika Kurzmann

Research output: Contribution to journalArticlepeer-review

Abstract

Quantum states in graphene are two-fold degenerate in spins, and two-fold in valleys. Both degrees of freedom can be utilized for qubit preparations. In our bilayer graphene quantum dots, we demonstrate that the valley g-factor gv, dened analogously to the spin g-factor gs for valley splitting in perpendicular magnetic field, is tunable by over a factor of four from 20 to 90, by gate voltage adjustments only. Larger gv results
from larger electronic dot sizes, determined from the charging energy. On our versatile device, bipolar operation, charging our quantum dot with charge carriers of the same or the opposite polarity as the leads, can be performed. Dots of both polarities are tunable to the first charge carrier, such that the transition from an electron to a hole dot by action of the plunger gate can be observed. Addition of gates easily extends the system to host tunable double dots.
Original languageEnglish
JournalNano Letters
Publication statusAccepted/In press - 29 Dec 2020

Research Beacons, Institutes and Platforms

  • National Graphene Institute

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