166 research outputs found
Kondo Quantum Criticality of Magnetic Adatoms in Graphene
We examine the exchange Hamiltonian for magnetic adatoms in graphene with
localized inner shell states. On symmetry grounds, we predict the existence of
a class of orbitals that lead to a distinct class of quantum critical points in
graphene, where the Kondo temperature scales as
near the critical coupling , and the local spin is effectively screened
by a \emph{super-ohmic} bath. For this class, the RKKY interaction decays
spatially with a fast power law . Away from half filling, we show
that the exchange coupling in graphene can be controlled across the quantum
critical region by gating. We propose that the vicinity of the Kondo quantum
critical point can be directly accessed with scanning tunneling probes and
gating.Comment: 4.1 pages, 3 figures. Added erratum correcting exponent nu=1/3. All
the other results remain vali
Magnetic exchange mechanism for electronic gap opening in graphene
We show within a local self-consistent mean-field treatment that a random
distribution of magnetic adatoms can open a robust gap in the electronic
spectrum of graphene. The electronic gap results from the interplay between the
nature of the graphene sublattice structure and the exchange interaction
between adatoms.The size of the gap depends on the strength of the exchange
interaction between carriers and localized spins and can be controlled by both
temperature and external magnetic field. Furthermore, we show that an external
magnetic field creates an imbalance of spin-up and spin-down carriers at the
Fermi level, making doped graphene suitable for spin injection and other
spintronic applications.Comment: 5 pages, 5 figure
Surface superconductivity in multilayered rhombohedral graphene: Supercurrent
The supercurrent for the surface superconductivity of a flat-band
multilayered rhombohedral graphene is calculated. Despite the absence of
dispersion of the excitation spectrum, the supercurrent is finite. The critical
current is proportional to the zero-temperature superconducting gap, i.e., to
the superconducting critical temperature and to the size of the flat band in
the momentum space
Induced magnetism in transition metal intercalated graphitic systems
We investigate the structure, chemical bonding, electronic properties, and
magnetic behavior of a three-dimensional graphitic network in aba and aaa
stacking with intercalated transition metal atoms (Mn, Fe, Co, Ni, and Cu).
Using density functional theory, we find induced spin-polarization of the C
atoms both when the graphene sheets are aba stacked (forming graphite) and aaa
stacked (resembling bi-layer graphene). The magnetic moment induced by Mn, Fe,
and Co turns out to vary from 1.38 {\mu}B to 4.10 {\mu}B, whereas intercalation
of Ni and Cu does not lead to a magnetic state. The selective induction of
spin-polarization can be utilized in spintronic and nanoelectronic
applications.Comment: 13 pages, 3 figures, 1 tabl
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