论文标题
石墨烯量子点中的壳填充和三角翘曲
Shell Filling and Trigonal Warping in Graphene Quantum Dots
论文作者
论文摘要
通过BiLayer石墨烯中的几个电子圆形量子点进行的传输测量显示了四个，八和十二的组的电导共振。这与双层石墨烯中的旋转和山谷变性性以及由三角翘曲引起的另外三倍的“ Minivalley Deneracy”相符。对于小电子数，这意味着小点大小和一个小的位移场，二维S-和P壳分别依次填充四个和八个电子。对于大于十二的电子数，随着点的大小和位移场的增加，单粒子基态将演变成三个变化的Minivalley基态。在我们的测量结果中观察到这些机制之间的过渡，可以通过频段结构计算来描述。磁场中的测量结果证实了Hund旋转量子点水平的第二个规则，强调了交换相互作用效应的重要性。
Transport measurements through a few-electron circular quantum dot in bilayer graphene display bunching of the conductance resonances in groups of four, eight and twelve. This is in accordance with the spin and valley degeneracies in bilayer graphene and an additional threefold 'minivalley degeneracy' caused by trigonal warping. For small electron numbers, implying a small dot size and a small displacement field, a two-dimensional s- and then a p-shell are successively filled with four and eight electrons, respectively. For electron numbers larger than twelve, as the dot size and the displacement field increase, the single-particle ground state evolves into a three-fold degenerate minivalley ground state. A transition between these regimes is observed in our measurements and can be described by band-structure calculations. Measurements in magnetic field confirm Hund's second rule for spin filling of the quantum dot levels, emphasizing the importance of exchange interaction effects.
