title: Coulomb Oscillations in a Gate-Controlled Few-Layer Graphene Quantum Dot.
abstract: Graphene quantum dots could be an ideal host for spin qubits and thus have been extensively investigated based on graphene nanoribbons and etched nanostructures; however, edge and substrate-induced disorders severely limit device functionality. Here, we report the confinement of quantum dots in few-layer graphene with tunable barriers, defined by local strain and electrostatic gating. Transport measurements unambiguously reveal that confinement barriers are formed by inducing a band gap via the electrostatic gating together with local strain induced constriction. Numerical simulations according to the local top-gate geometry confirm the band gap opening by a perpendicular electric field. We investigate the magnetic field dependence of the energy-level spectra in these graphene quantum dots. Experimental results reveal a complex evolution of Coulomb oscillations with the magnetic field, featuring kinks at level crossings. The simulation of energy spectrum shows that the kink features and the magnetic field dependence are consistent with experimental observations, implying the hybridized nature of energy-level spectrum of these graphene quantum dots.
authors.affiliation: Center for Quantum Information, IIIS, Tsinghua University , Beijing 100084, China.
authors.forename: Yipu
authors.initials: Y
authors.lastname: Song
authors.affiliation: Center for Quantum Information, IIIS, Tsinghua University , Beijing 100084, China.|Department of Physics, Tsinghua University , Beijing 100084, China.
authors.forename: Haonan
authors.initials: H
authors.lastname: Xiong
authors.affiliation: Center for Quantum Information, IIIS, Tsinghua University , Beijing 100084, China.|Department of Physics, Tsinghua University , Beijing 100084, China.
authors.forename: Wentao
authors.initials: W
authors.lastname: Jiang
authors.affiliation: Center for Quantum Information, IIIS, Tsinghua University , Beijing 100084, China.
authors.forename: Hongyi
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Center for Quantum Information, IIIS, Tsinghua University , Beijing 100084, China.
authors.forename: Xiao
authors.initials: X
authors.lastname: Xue
authors.affiliation: Center for Quantum Information, IIIS, Tsinghua University , Beijing 100084, China.
authors.forename: Cheng
authors.initials: C
authors.lastname: Ma
authors.affiliation: Center for Quantum Information, IIIS, Tsinghua University , Beijing 100084, China.
authors.forename: Yulin
authors.initials: Y
authors.lastname: Ma
authors.affiliation: Center for Quantum Information, IIIS, Tsinghua University , Beijing 100084, China.
authors.forename: Luyan
authors.initials: L
authors.lastname: Sun
authors.affiliation: Center for Quantum Information, IIIS, Tsinghua University , Beijing 100084, China.
authors.forename: Haiyan
authors.initials: H
authors.lastname: Wang
authors.affiliation: Center for Quantum Information, IIIS, Tsinghua University , Beijing 100084, China.|Department of Physics, University of Michigan , Ann Arbor, Michigan 48109, United States.
authors.forename: Luming
authors.initials: L
authors.lastname: Duan
keywords: Coulomb oscillation; Few-layer graphene; Landau levels; quantum dot; tunable barriers