title: Observation of Landau levels on nitrogen-doped flat graphite surfaces without external magnetic fields.
abstract: 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 report the observation of 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 of π electrons that takes place at the perimeter of high-potential domains surrounded by positively charged substituted graphitic-nitrogen atoms.
authors.affiliation: Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan.|Tsukuba Research Center for Interdisciplinary Materials Science (TIMS) &Center for Integrated Research in Fundamental Science and Engineering (CiRfSE), University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Kondo
authors.affiliation: Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan.
authors.forename: Donghui
authors.initials: D
authors.lastname: Guo
authors.affiliation: Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan.
authors.forename: Taishi
authors.initials: T
authors.lastname: Shikano
authors.affiliation: Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Suzuki
authors.affiliation: Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan.
authors.forename: Masataka
authors.initials: M
authors.lastname: Sakurai
authors.affiliation: Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan.
authors.forename: Susumu
authors.initials: S
authors.lastname: Okada
authors.affiliation: Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan.|Tsukuba Research Center for Interdisciplinary Materials Science (TIMS) &Center for Integrated Research in Fundamental Science and Engineering (CiRfSE), University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan.
authors.forename: Junji
authors.initials: J
authors.lastname: Nakamura