Zheng Qi, Zhuang Yu-Chen, Sun Qing-Feng, He Lin
Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, 100875, Beijing, People's Republic of China.
International Center for Quantum Materials, School of Physics, Peking University, 100871, Beijing, China.
Nat Commun. 2022 Mar 24;13(1):1597. doi: 10.1038/s41467-022-29251-2.
The relativistic massless charge carriers with a Fermi velocity of about c/300 in graphene enable us to realize two distinct types of resonances (here, c is the speed of light in vacuum). One is the electron whispering-gallery mode in graphene quantum dots arising from the Klein tunneling of the massless Dirac fermions. The other is the atomic collapse state, which has never been observed in experiment with real atoms due to the difficulty of producing heavy nuclei with charge Z > 170; however, they can be realized near a Coulomb impurity in graphene with a charge Z ≥ 1 because of the "small" velocity of the Dirac excitations. Here we demonstrate that both the electron whispering-gallery modes and atomic collapse states coexist in graphene/WSe heterostructure quantum dots due to the Coulomb-like potential near their edges. By applying a perpendicular magnetic field, we explore the evolution from the atomic collapse states to unusual Landau levels in the collapse regime.
石墨烯中具有约c/300费米速度的相对论无质量电荷载流子使我们能够实现两种不同类型的共振（这里，c是真空中的光速）。一种是石墨烯量子点中的电子回音壁模式，它源于无质量狄拉克费米子的克莱因隧穿。另一种是原子坍缩态，由于难以产生电荷Z > 170的重原子核，在真实原子的实验中从未观察到这种状态；然而，由于狄拉克激发的“小”速度，它们可以在电荷Z ≥ 1的石墨烯中的库仑杂质附近实现。在这里，我们证明由于石墨烯/硒化钨异质结构量子点边缘附近类似库仑的势，电子回音壁模式和原子坍缩态共存。通过施加垂直磁场，我们探索了在坍缩区域中从原子坍缩态到异常朗道能级的演化。
