Evidence for semiconducting behavior with a narrow band gap of Bernal graphite

García, N.; Esquinazi, P.; Barzola-Quiquia, J.; Dusari, S.

doi:10.48550/arxiv.1106.0437

Cited by 3 publications

(5 citation statements)

References 52 publications

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“…Note that the semiconductinglike behavior with a saturation at low temperatures is observed at all distances between the voltage electrodes indicating that this dependence is intrinsic and not related to the sample size, supporting the conclusions of Ref. 13. In fact, using the same parallel resistance model and the exponential temperature dependence appropriate for semiconductors as in Ref.…”

Section: Methodssupporting

confidence: 84%

“…In fact, using the same parallel resistance model and the exponential temperature dependence appropriate for semiconductors as in Ref. 13, the obtained energy gap E g /k B ≃ 350 K is independent of the distance between electrodes.…”

Section: Methodsmentioning

confidence: 70%

“…12 and from a HOPG sample with 0.35 • rocking curve width. Micro-Raman measurements indicate that even samples of 10 nm thickness are of good quality without showing any contribution of the defect-related D-peak at 1350 cm −1 [13].…”

Section: Methodsmentioning

confidence: 99%

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Length dependence of the resistance in graphite: Influence of ballistic transport

Esquinazi

Barzola‐Quiquia

Dusari

et al. 2012

Journal of Applied Physics

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Using a linear array of voltage electrodes with a separation of several micrometers on a 20 nm thick and 30 µm long multigraphene sample we show that the measured resistance does not follow the usual length dependence according to Ohm's law. The deviations can be quantitatively explained taking into account Sharvin-Knudsen formula for ballistic transport. This allows us to obtain without free parameters the mean free path of the carriers in the sample at different temperatures. In agreement with recently reported values obtained with a different experimental method, we obtain that the carrier mean free path is of the order of ∼ 2 µm with a mobility µ ∼ 10 7 cm 2 V −1 s −1 . The results indicate that the usual Ohm's law is not adequate to calculate the absolute resistivity of mesoscopic graphite samples.

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Section: Methodssupporting

confidence: 84%

Section: Methodsmentioning

confidence: 70%

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Length dependence of the resistance in graphite: Influence of ballistic transport

Esquinazi

Barzola‐Quiquia

Dusari

et al. 2012

Journal of Applied Physics

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“…More generally our findings point to an inhomogeneous doping and a semiconducting gap in graphite (see also Ref. [18]). The linear orbital NMR is a unique signature of the timereversal symmetry breaking.…”

Section: (1)supporting

confidence: 74%

Extraordinary magnetoresistance in graphite: experimental evidence for the time-reversal symmetry breaking

Kopelevich

Silva

Camargo

et al. 2013

J. Phys.: Condens. Matter

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We report an unusual highly-anisotropic in-plane magneto-resistance (MR) in graphite. In a certain current direction MR is negative and linear in low fields with a crossover to a positive MR at higher fields, while in a perpendicular current direction we observe a giant super-linear positive MR. These extraordinary MRs are respectively explained by a hopping magneto-conductance via non-zero angular momentum orbitals, and by the magneto-conductance of inhomogeneous media. The linear negative orbital MR is a unique signature of the broken time-reversal symmetry (TRS) in graphite. While some local paramagnetic centers could be responsible for the broken TRS, the observed large diamagnetism suggests a more intriguing mechanism of this breaking, involving superconducting clusters with unconventional (chiral) order parameters and spontaneously generated normal-state current loops in graphite.PACS numbers: 72.20. Ee, 72.80.Le, 72.20.My, 73.61.Ph The transverse magneto-resistance (MR) in a magnetic field B along the z-axis defined as M R = σ xx σ xx (0)/(σ 2 xx + σ 2 xy ) − 1 in terms of the conductivity tensor σ ik (B), is a sensitive probe of the electron transport mechanism in doped semiconductors and metals. In an isotropic medium with the Bloch electrons it is positive and quadratic in B, except the open Fermi surfaces, where for some specific directions of B the positive MR is linear in B. In the hopping regime with localized carriers MR is caused by a strong magnetic field dependence of the exponential asymptotic of bound state wave functions at a remote distance from a donor (or an acceptor), which leads to a significant positive MR, which is also quadratic in low magnetic fields [2].However, there is a substantial number of semiconductors and semimetals (e. g. bismuth) where open Fermi surfaces are not feasible, but the positive MR is linear. One of the theoretical possibilities for such a phenomenon is a so-called quantum magnetoresistance in semimetals having pockets of the Fermi surface with a small or even zero effective mass (as the Dirac fermions in graphite and graphene), which might be in the ultra-quantum limit at rather low magnetic fields [3].On the other hand, there is anomalous negative MR (NMR) first observed in some hopping systems, for instance in amorphous germanium and silicon. More recently a linear NMR has been observed in the longitudinal c-axis interlayer current in graphite at high magnetic fields assigned to a growing population of the zero-energy Landau level of quasi-two-dimensional Dirac fermions with the increasing magnetic field [4].Here we report a low-field transverse MR in bulk quasitwo-dimensional graphite samples, which is giant ( 1400% at 2K and B = 200 mT) and positive in one in-plane current direction, and linear and negative (below 80 mT) in the other direction, when the magnetic field is applied perpendicular to the planes. These observations are quantitatively explained in the framework of the magnetotransport of inhomogeneous low-carrier semiconductors [5] and of a ho...

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“…However, this has been solved later by Drut and Lähde 6 using Monte Carlo simulations and proved that a band gap appears for the case of ideal graphene and small N F . The existence of a narrow gap has been recently shown by transport measurements in mesoscopic, thin graphite samples 7 . The existence of an energy gap will solve automatically the apparent difficulties between holes and electrons discussed before and the dispersion at low energies will be rather parabolic or other complicated behavior but not linear.…”

mentioning

confidence: 84%

Comment on "Dirac cones reshaped by interaction effects in suspended graphene" by Elias et al., Nature Physics 7, 701 (2011)

García,

Esquinazi,

Pasa

2011

Preprint

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Evidence for semiconducting behavior with a narrow band gap of Bernal graphite

Cited by 3 publications

References 52 publications

Length dependence of the resistance in graphite: Influence of ballistic transport

Length dependence of the resistance in graphite: Influence of ballistic transport

Extraordinary magnetoresistance in graphite: experimental evidence for the time-reversal symmetry breaking

Comment on "Dirac cones reshaped by interaction effects in suspended graphene" by Elias et al., Nature Physics 7, 701 (2011)

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