Department of Physics, Washington University in St. Louis, 1 Brookings Drive, St. Louis, Missouri 63130, USA.
National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0044, Japan.
Phys Rev Lett. 2018 Jan 26;120(4):047401. doi: 10.1103/PhysRevLett.120.047401.
We study the infrared cyclotron resonance of high-mobility monolayer graphene encapsulated in hexagonal boron nitride, and simultaneously observe several narrow resonance lines due to interband Landau-level transitions. By holding the magnetic field strength B constant while tuning the carrier density n, we find the transition energies show a pronounced nonmonotonic dependence on the Landau-level filling factor, ν∝n/B. This constitutes direct evidence that electron-electron interactions contribute to the Landau-level transition energies in graphene, beyond the single-particle picture. Additionally, a splitting occurs in transitions to or from the lowest Landau level, which is interpreted as a Dirac mass arising from coupling of the graphene and boron nitride lattices.
我们研究了封装在六方氮化硼中的高迁移率单层石墨烯的红外回旋共振，并同时观察到由于带间朗道能级跃迁而产生的几个窄共振线。通过保持磁场强度 B 不变而调节载流子密度 n，我们发现跃迁能量显示出对朗道能级填充因子 ν∝n/B 的明显非单调依赖性。这直接证明了电子-电子相互作用对石墨烯中朗道能级跃迁能量的贡献，超出了单粒子图像。此外，在从或到最低朗道能级的跃迁中会发生分裂，这被解释为来自石墨烯和氮化硼晶格耦合的狄拉克质量。
