Origin of the Landau levels generation at the flat graphite surfaces without external magnetic fields

2015 Fiscal Year Final Research Report

• Project/Area Number: 25390074
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Thin film/Surface and interfacial physical properties
• Research Institution: University of Tsukuba
• Principal Investigator: Kondo Takahiro 筑波大学, 数理物質系, 准教授 (70373305)
• Co-Investigator(Renkei-kenkyūsha): NAKAMURA Junji 筑波大学, 数理物質系, 教授 (40227905)
• Project Period (FY): 2013-04-01 – 2016-03-31
• Keywords: グラファイト / グラフェン / ランダウ準位 / 走査トンネル分光 / 擬磁場

Outline of Final Research Achievements

Under perpendicular external magnetic fields, two-dimensional carriers exhibit Landau levels (LLs). However, it has recently been reported that LLs have been observed on graphene and graphite surfaces without external magnetic fields being applied. These anomalous LLs have been ascribed primarily to a strain of graphene sheets, leading to in-plane hopping modulation of electrons. Here, we have observed the LLs of massive Dirac fermions on atomically flat areas of a nitrogen-doped graphite surface in the absence of external magnetic fields. The corresponding magnetic fields were estimated to be as much as approximately 100 T. The generation of the LLs at the area with negligible strain can be explained by inequivalent hopping ofelectrons that takes place at the perimeter of high-potential domains surrounded by positively charged substituted graphitic-nitrogen atoms.

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