985 research outputs found
Phase analysis of quantum oscillations in graphite
The quantum de Haas van Alphen (dHvA) and Shubnikov de Haas (SdH)
oscillations measured in graphite were decomposed by pass-band filtering onto
contributions from three different groups of carriers. We develop the
two-dimensional phase analysis method which allows to identify these carriers
as (i) minority holes having two-dimensional (2D) parabolic massive spectrum,
(ii) majority electrons, also massive but with intermediate 2D-3D spectrum, and
(iii) majority holes with 2D Dirac-like spectrum which seems to be responsible
for the unusual strongly-correlated electronic phenomena in graphite.Comment: latest version as was published in PR
Comment on "Consistent Interpretation of the Low-Temperature Magnetotransport in Graphite Using the Slonczewski-Weiss-McClure 3D Band-Structure Calculations" (arXiv:0902.1925)
In 2004 we have shown that substantial part of conductivity in graphite is
provided by holes with massless linear spectrum - Dirac Fermions that coexist
with massive normal carriers - electrons. In a recent Letter [Phys. Rev. Lett.
102, 166403 (2009), arXiv:0902.1925] Schneider et al. revised our conclusion
pointed that both types of carriers are massive. Since both groups use the same
method of phase determination of Shubnikov de Haas oscillation we comment here
that the controversy originates from the improper treatment of experimental
results in Schneider2009 et al
Dirac and Normal Fermions in Graphite and Graphene: Implications to the Quantum Hall Effect
Spectral analysis of Shubnikov de Haas (SdH) oscillations of
magnetoresistance and of Quantum Hall Effect (QHE) measured in quasi-2D highly
oriented pyrolytic graphite (HOPG) [Phys. Rev. Lett. 90, 156402 (2003)] reveals
two types of carriers: normal (massive) electrons with Berry phase 0 and
Dirac-like (massless) holes with Berry phase pi. We demonstrate that recently
reported integer- and semi-integer QHE for bi-layer and single-layer graphenes
take place simultaneously in HOPG samples.Comment: 4 page
Oscillating Nernst-Ettingshausen effect in Bismuth across the quantum limit
In elemental Bismuth, 10 atoms share a single itinerant electron.
Therefore, a moderate magnetic field can confine electrons to the lowest Landau
level. We report on the first study of metallic thermoelectricity in this
regime. The main thermoelectric response is off-diagonal with an oscillating
component several times larger than the non-oscillating background. When the
first Landau level attains the Fermi Energy, both the Nernst and the
Ettingshausen coefficients sharply peak, and the latter attains a
temperature-independent maximum. A qualitative agreement with a theory invoking
current-carrying edge excitations is observed.Comment: Final published versio
Embedded monopoles in quark eigenmodes in SU(2) Yang-Mills Theory
We study the embedded QCD monopoles (``quark monopoles'') using low-lying
eigenmodes of the overlap Dirac operator in zero- and finite-temperature SU(2)
Yang-Mills theory on the lattice. These monopoles correspond to the
gauge-invariant hedgehogs in the quark-antiquark condensates. The monopoles
were suggested to be agents of the chiral symmetry restoration since their
cores should suppress the chiral condensate. We study numerically the scalar,
axial and chirally invariant definitions of the embedded monopoles and show
that the monopole densities are in fact globally anti-correlated with the
density of the Dirac eigenmodes. We observe, that the embedded monopoles
corresponding to low-lying Dirac eigenvalues are dense in the chirally
invariant (high temperature) phase and dilute in the chirally broken (low
temperature) phase. We find that the scaling of the scalar and axial monopole
densities towards the continuum limit is similar to the scaling of the
string-like objects while the chirally invariant monopoles scale as membranes.
The excess of gluon energy at monopole positions reveals that the embedded QCD
monopole possesses a gluonic core, which is, however, empty at the very center
of the monopole.Comment: 29 pages, 27 figures, RevTeX 4.0; revised to match the published
version (clarifying remarks, references and acknowledgments are added
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