Ghahari Fereshte, Walkup Daniel, Gutiérrez Christopher, Rodriguez-Nieva Joaquin F, Zhao Yue, Wyrick Jonathan, Natterer Fabian D, Cullen William G, Watanabe Kenji, Taniguchi Takashi, Levitov Leonid S, Zhitenev Nikolai B, Stroscio Joseph A
Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
Maryland NanoCenter, University of Maryland, College Park, MD 20742, USA.
Science. 2017 May 26;356(6340):845-849. doi: 10.1126/science.aal0212.
The phase of a quantum state may not return to its original value after the system's parameters cycle around a closed path; instead, the wave function may acquire a measurable phase difference called the Berry phase. Berry phases typically have been accessed through interference experiments. Here, we demonstrate an unusual Berry phase-induced spectroscopic feature: a sudden and large increase in the energy of angular-momentum states in circular graphene p-n junction resonators when a relatively small critical magnetic field is reached. This behavior results from turning on a π Berry phase associated with the topological properties of Dirac fermions in graphene. The Berry phase can be switched on and off with small magnetic field changes on the order of 10 millitesla, potentially enabling a variety of optoelectronic graphene device applications.
在系统参数围绕闭合路径循环一周后，量子态的相位可能不会回到其初始值；相反，波函数可能会获得一个可测量的相位差，即贝里相位。贝里相位通常是通过干涉实验来观测的。在此，我们展示了一种由贝里相位引起的不寻常光谱特征：当达到一个相对较小的临界磁场时，圆形石墨烯 p-n 结谐振器中角动量态的能量会突然大幅增加。这种行为源于与石墨烯中狄拉克费米子拓扑性质相关的 π 贝里相位的开启。通过大约 10 毫特斯拉的小磁场变化，贝里相位可以开启和关闭，这可能使石墨烯在各种光电器件应用中得以实现。
