Magnetothermal conductivity of highly oriented pyrolytic graphite in the quantum limit

Ocaña, Roberto; Esquinazi, P.; Kempa, H.; Torres, J. H. S.; Kopelevich, Y.

doi:10.1103/physrevb.68.165408

Cited by 20 publications

(39 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The enhancement of electron-phonon scattering near the Landau level intersection described in our work is possibly responsible for some features observed in magnetothermal conductivity of highly oriented pyrolitic graphite. 31,32 In the presence of nonequilibrium phonons 4-7 the electron-phonon scattering mechanism might become dominant.…”

Section: ͑36͒mentioning

confidence: 99%

Electron-phonon scattering at the intersection of two Landau levels

2006

View full text Add to dashboard Cite

We predict a double-resonant feature in the magnetic field dependence of the phonon-mediated longitudinal conductivity xx of a two-subband quasi-two-dimensional electron system in a quantizing magnetic field. The two sharp peaks in xx appear when the energy separation between two Landau levels belonging to different size-quantization subbands is favorable for acoustic-phonon transitions. One-phonon and two-phonon mechanisms of electron conductivity are calculated and compared. The phonon-mediated interaction between the intersecting Landau levels is considered and no avoided crossing is found at thermal equilibrium.

show abstract

Section: ͑36͒mentioning

confidence: 99%

Electron-phonon scattering at the intersection of two Landau levels

2006

View full text Add to dashboard Cite

show abstract

“…Graphitic systems are nowadays a field of intensive activity [1]. There have been observations of quantum Hall effect in HOPG [2,3] as well as very large anisotropy in the electrical conductance (ratio between current parallel to perpendicular to the graphene planes) larger than 10 4 at room temperature [1]. Graphite looks as a good conductor in plane and an insulator between planes leading to a weak screening to external electric fields [4].…”

mentioning

confidence: 99%

Sample-Size Effects in the Magnetoresistance of Graphite

Muñoz

Garcı́a

et al. 2007

Phys. Rev. Lett.

Self Cite

View full text Add to dashboard Cite

We present a study of the magnetoresistance of highly oriented pyrolytic graphite (HOPG) as a function of the sample size. Our results show unequivocally that the magnetoresistance reduces with the sample size even for samples of hundreds of micrometers size. This sample size effect is due the large mean free path and Fermi wavelength of carriers in graphite and may explain the observed practically absence of magnetoresistance in micrometer confined small graphene samples where quantum effects should be at hand. These were not taken into account in the literature yet and ask for a revision of experimental and theoretical work on graphite.PACS numbers: 81.05. Uw,72.80.Cw Graphitic systems are nowadays a field of intensive activity [1]. There have been observations of quantum Hall effect in HOPG [2,3] as well as very large anisotropy in the electrical conductance (ratio between current parallel to perpendicular to the graphene planes) larger than 10 4 at room temperature [1]. Graphite looks as a good conductor in plane and an insulator between planes leading to a weak screening to external electric fields [4]. This means that an external electric field penetrates by tens of nanometers in graphite, in contrast to a normal metal where the field is screened in the first atomic layers. In fact the dielectric constant of graphite at optical frequencies is positive, insulator like (ǫ plane = 5.6 + i7.0, ǫ c = 2.25) [5,6]. Electric field microscopy [7] detects that regions of graphite are more insulating than others upon the interconnections of graphite planes produced by defects and their overall density that influences the density of states and the Fermi level. The material exhibits a huge magnetic field driven metal-insulator transition [1,8]. Its band structure and interband transitions with electron and hole carriers manifest in a huge ordinary magnetoresistance (OMR) [2,9]. All these effects happen in macroscopic size samples of the order of millimeters.A large research activity has been recently started on a few graphene layers (FLG) [10] with typical size of a few microns. Strikingly, the OMR in FLG samples is practically suppressed even at T < 4 K, in contrast to bulk HOPG or Kish graphite where the OMR is 1000% at B 0.5 T at low temperatures [1]. Earlier work with graphite samples in the micrometer range showed similar behavior [11,12]. However, the question on what happens when the graphite sample size is reduced has not been correctly addressed and the experimental data may need a new interpretation. The size of the sample is very important for defining the properties of the system because the de-Broglie wavelength for massless Dirac6 m/s is the Fermi velocity and a typical Fermi energy k B E F 100 K) or for massive carriers with effective mass m ⋆ 0.01m, λ m = h/ √ 2m ⋆ E F , as well as the Fermi wavelength λ F ∼ 2πn −1/2 are of the order of microns or larger due to the low density of Dirac and massive fermions. Moreover, one can show that in such micron size systems new quantum mechanical oscillations ap...

show abstract

“…Nevertheless, it is surprising that for the paradigm of strongly anisotropic systems, graphite, no clear evidence for the QHE has been published till 2003 [1,2,3]. The main obstacle to obtain clear evidence for the QHE in graphite is the sample quality, i.e.…”

mentioning

confidence: 99%

“…Measurements with the Corbino-disk configuration support this result and indicate that the quasi-linear and non-saturating longitudinal magnetoresistance in graphite is governed by the Hall effect in agreement with a recent theoretical model for disordered semiconductors. Recent experimental [1,2,3,4,5,6] and theoretical [7,8,9] work demonstrates the occurrence of correlated phenomena in the electron system of graphite, indicating that the classical view of the physics of its magnetotransport properties is not adequate. Besides, the quantum Hall effect (QHE) [1] as well as evidence for Dirac fermions (massless particles due to the linear dispersion relation) [5] have been reported for bulk samples of highly oriented pyrolytic graphite of high quality.…”

Section: Introductionmentioning

confidence: 99%

Integer quantum Hall effect in graphite

Kempa

Esquinazi

Kopelevich

2006

Solid State Communications

Self Cite

View full text Add to dashboard Cite

We present Hall effect measurements on highly oriented pyrolytic graphite that indicate the occurrence of the integer quantum-Hall-effect. The evidence is given by the observation of regular plateau-like structures in the field dependence of the transverse conductivity obtained in van der Pauw configuration. Measurements with the Corbino-disk configuration support this result and indicate that the quasi-linear and non-saturating longitudinal magnetoresistance in graphite is governed by the Hall effect in agreement with a recent theoretical model for disordered semiconductors. Recent experimental [1,2,3,4,5,6] and theoretical [7,8,9] work demonstrates the occurrence of correlated phenomena in the electron system of graphite, indicating that the classical view of the physics of its magnetotransport properties is not adequate. Besides, the quantum Hall effect (QHE) [1] as well as evidence for Dirac fermions (massless particles due to the linear dispersion relation) [5] have been reported for bulk samples of highly oriented pyrolytic graphite of high quality. Recently published results obtained on bulk graphite [10,11], a few layers thick graphite [12], and in graphene (single graphite layer) [13,14] have confirmed both observations and showed that in graphene the QHE is anomalous in that the contribution of the Dirac fermions makes the plateaus to occur at half-integer filling factors. Certainly, the understanding of the electronic properties of graphite is necessary for the development of advanced technology of the graphite-related nanomaterials.

show abstract

Magnetothermal conductivity of highly oriented pyrolytic graphite in the quantum limit

Cited by 20 publications

References 40 publications

Electron-phonon scattering at the intersection of two Landau levels

Electron-phonon scattering at the intersection of two Landau levels

Sample-Size Effects in the Magnetoresistance of Graphite

Integer quantum Hall effect in graphite

Contact Info

Product

Resources

About