Settnes Mikkel, Power Stephen R, Brandbyge Mads, Jauho Antti-Pekka
Center for Nanostructured Graphene (CNG), Department of Micro- and Nanotechnology Engineering, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
Department of Photonics Engineering, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
Phys Rev Lett. 2016 Dec 30;117(27):276801. doi: 10.1103/PhysRevLett.117.276801. Epub 2016 Dec 28.
The energy band structure of graphene has two inequivalent valleys at the K and K^{'} points of the Brillouin zone. The possibility to manipulate this valley degree of freedom defines the field of valleytronics, the valley analogue of spintronics. A key requirement for valleytronic devices is the ability to break the valley degeneracy by filtering and spatially splitting valleys to generate valley polarized currents. Here, we suggest a way to obtain valley polarization using strain-induced inhomogeneous pseudomagnetic fields (PMFs) that act oppositely on the two valleys. Notably, the suggested method does not involve external magnetic fields, or magnetic materials, unlike previous proposals. In our proposal the strain is due to experimentally feasible nanobubbles, whose associated PMFs lead to different real space trajectories for K and K^{'} electrons, thus allowing the two valleys to be addressed individually. In this way, graphene nanobubbles can be exploited in both valley filtering and valley splitting devices, and our simulations reveal that a number of different functionalities are possible depending on the deformation field.
石墨烯的能带结构在布里渊区的K点和K'点有两个不等价的谷。操纵这种谷自由度的可能性定义了谷电子学领域，即自旋电子学的谷类似物。谷电子学器件的一个关键要求是能够通过过滤和空间分离谷来打破谷简并，以产生谷极化电流。在此，我们提出一种利用应变诱导的非均匀赝磁场（PMF）来获得谷极化的方法，该赝磁场对两个谷的作用相反。值得注意的是，与之前的提议不同，所提出的方法不涉及外部磁场或磁性材料。在我们的提议中，应变是由实验上可行的纳米气泡引起的，其相关的赝磁场导致K和K'电子具有不同的实空间轨迹，从而使得两个谷能够被分别处理。通过这种方式，石墨烯纳米气泡可用于谷过滤和谷分裂器件，并且我们的模拟表明，根据变形场的不同，可能实现许多不同的功能。
