中文摘要：

在20mK的极低温下测量了石墨烯纳米带量子点的电子输运性质，观测到清晰的库仑阻塞菱形块和对应量子点激发态的电导峰．对库仑阻塞近邻电导峰间距和峰值进行了统计分析，发现其统计分布分别满足无规矩阵理论描述的Wigner-Dyson分布和Porter-Thomas分布，说明石墨烯纳米带量子点在低温下出现了量子混沌现象．还讨论了这种长方形量子点中量子混沌的可能成困．

英文摘要：

The electron transport property of a graphene nanoribbon （GNR） quantum dot in a dilution refrigerator at temperature 20 mK is studied. The Coulomb blockade diamonds and excited energy levels of the quantum dot are clearly observed. It is found that the statistical distribution of the spacing between the nearest-neighboring Coulomb blockade peaks and that of the individual peak height are consistent respectively with the typical Wigner-Dyson distribution and Porter-Thomas distribution as prescribed by the random matrix theory for a quantum chaotic system. Thus, our results demonstrate that the GNR quantum dot is a quantum chaotic system at low temperatures. The possible origin of this phenomenon is also discussed.