SKM 2023 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 9: Focus Session: Graphene quantum dots (joint session HL/TT)
HL 9.4: Invited Talk
Monday, March 27, 2023, 16:45–17:15, POT 251
Single-shot spin and valley Pauli blockade read-out in bilayer graphene quantum dots — •Chuyao Tong1, Rebekka Garreis1, Wister Wei Huang1, Annika Kurzmann1,2, Jocelyn Terle1, Samuel Jele1, Kenji Watanabe3, Takashi Taniguchi3, Thomas Ihn1, and Klaus Ensslin1 — 1ETH Zurich, CH-8093 Zurich, Switzerland — 2RWTH Aachen University, Aachen, 52074, Germany — 3National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
In bilayer graphene quantum dots, apart from spins up and down, the additional valley degree of freedom K- and K+ gives rise to an unconventional single-dot two-carrier ground state: spin-triplet valley-singlet, altering the canonical even-odd double dot Pauli spin blockade picture. This ground state can be switched to a spin-singlet valley-triplet by a perpendicular magnetic field, allowing us to switch between valley-blockade at low, and spin-blockade at higher magnetic field for the two-carrier Pauli blockade (1,1) to (0,2). We employ charge sensing technology and perform single-shot Pauli blockade read-out at the two field regimes, probing characteristic relaxation times T1 between spin or valley -triplet and -singlet. The spin-T1 is measured to be up to 60ms, drastically decreasing with increasing inter-dot tunnel coupling and corroborating with recent experiments performed with single-dot Elzerman read-out. Moreover, we observe exceedingly long valley T1 longer than 500ms, robust with inter-dot tunnel coupling. These promisingly long spin- and valley T1 herald for long-living spin and valley bilayer graphene quantum dot qubits.