Absence of metal–insulator transition and coherent interlayer transport in oriented graphite in parallel magnetic fields

Abstract

Measurements of the magnetoresistivity of graphite with a high degree of control of the angle between the sample and magnetic field indicate that the metal-insulator transition (MIT), shown to be induced by a magnetic field applied perpendicular to the layers, does not appear in parallel field orientation. Furthermore, we show that interlayer transport is coherent in less ordered samples and high magnetic fields, whereas appears to be incoherent in less disordered samples. Our results demonstrate the two-dimensionality of the electron system in ideal graphite samples. Recent experimental and theoretical studies of graphite have renewed the interest in this system [1,2,3,4,5,6,7,8,9,10]. Experimental results show that, contrary to the common belief, the transport and magnetic properties of graphite cannot be accounted for by semiclassical models. Experiment and theory raise a number of questions concerning the coupling between the graphite layers. The understanding of the transport properties is of primary interest and can provide a fundamental contribution to the physics of two-dimensional (2D) systems in general. In this letter we deal with two important open questions: 1. A MIT appears both in the in-plane [1,3,4] and out-of-plane [5] resistivity induced by a magnetic field B applied perpendicular to the graphite layers, i.e. B||c-axis. Based on magnetization data [2] and the found 2D scaling similar to that in the MIT of Si-MOSFETs (metal-oxide-semiconductor field-effecttransitor) [11], and Bi-films [13], the MIT in graphite has been

Magnetism in carbon structures

“…At room temperature and for a sample with FWHM = 0.4 • , due to the χ || component a value of the order of −1.7 × 10 −7 emu/gOe ≪ χ ⊥ would be measured for fields applied nominally parallel to the planes. The effect of this internal misalignment has been verified by electrical conductivity measurements [8].…”

Graphene Physics in Graphite

“…Indeed, high-resolution angle-dependent measurements of ρ c (θ) reveal a maximum (the so-called "coherent resistivity peak") when the magnetic field is applied parallel to the graphene layers for less-ordered graphite samples with mosaicity >1°. [20] In contrast, for well-ordered HOPG samples with mosaicity ≤0.4°, no maximum has been observed. This result suggests incoherent transport along the c-axis, and therefore the existence of a 2D FS in "ideal" graphite.…”

Raman Scattering from High-Frequency Phonons in Supported n-Graphene Layer Films

“…Several interesting reports of unusual electrical transport in ultra-thin graphite films have appeared recently [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] . These films are comprised of only a few atomic layers of sp2-bonded carbon known as "graphene" layers.…”