Supermetallic conductivity in bromine-intercalated graphite (original) (raw)
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Ultrapure multilayer graphene in bromine-intercalated graphite
We investigate the optical properties of bromine-intercalated highly orientated pyrolytic graphite (Br-HOPG) and provide an interpretation of the data. We observe absorption features below 620 meV which are absent in the absorption spectrum of graphite. Comparing our results with those of theoretical studies on graphite, single-and bilayer graphene, as well as recent optical studies of multilayer graphene, we conclude that Br-HOPG contains the signatures of ultrapure bilayer graphene, ultrapure single-layer graphene, and graphite. The observed supermetallic conductivity of Br-HOPG is identified with the presence of very high mobility ( 121 000 cm 2 V −1 s −1 at room temperature and at very high carrier density), multilayer graphene components in our sample. This could provide an avenue for single-and multilayer graphene research.
Magnetic-field-induced superconductor–metal-insulator transitions in bismuth metal graphite
Physical Review B, 2002
Bismuth-metal graphite (MG) has a unique layered structure where Bi nanoparticles are encapsulated between adjacent sheets of nanographites. The superconductivity below Tc (= 2.48 K) is due to Bi nanoparticles. The Curie-like susceptibility below 30 K is due to conduction electrons localized near zigzag edges of nanographites. A magnetic-field induced transition from metallic to semiconductor-like phase is observed in the in-plane resistivity ρa around Hc (≈ 25 kOe) for both H⊥c and H c (c: c axis). A negative magnetoresistance in ρa for H⊥c (0< H ≤3.5 kOe) and a logarithmic divergence in ρa with decreasing temperature for H c (H > 40 kOe) suggest the occurrence of two-dimensional weak localization effect.
Far-infrared magnetoreflection studies of graphite intercalated with bromine
Physical Review B
An estimate of the hole generation rate in graphite-bromine residue compounds has been made from the interpretation of far-infrared magnetoreflection data. From the cutoff of the (1,2) Landau level transition due to the lowering of the Fermi energy upon bromine intercalation, we estimate that one hole is generated by 55 + 10 Br2 intercalate molecules. This result is shown to be consistent with estimates based on transport measurements. Furthermore, the observed magnetoreflection resonances confirm that for these compounds (& 1 mole% Br,) the electronic structure in the band overlap region is well described by the Slonczewski-Weiss-McClure band model for approximately the same values of the band parameters as for pure graphite.
Bromination of graphene and graphite
Physical Review B, 2011
For full reference please see: Phys. Rev. B 83, 045411, 2011 We present a density functional theory study of low density bromination of graphene and graphite, finding significantly different behaviour in these two materials. On graphene we find a new Br2 form where the molecule sits perpendicular to the graphene sheet with an extremely strong molecular dipole. The resultant Br + -Br − has an empty pz-orbital located in the graphene electronic π-cloud. Bromination opens a small (86meV) band gap and strongly dopes the graphene. In contrast, in graphite we find Br2 is most stable parallel to the carbon layers with a slightly weaker associated charge transfer and no molecular dipole. We identify a minimum stable Br2 concentration in graphite, finding low density bromination to be endothermic. Graphene may be a useful substrate for stabilising normally unstable transient molecular states. PACS numbers: 31.15.A-73.22.Pr 81.05.uf 37.30.+i
In following research paper, the new possible solution for the real physical conduction mechanism, at first, in monolayer Graphene, is proposed. A general model how electrons travel and transport energy through these conductors will be based on benzene molecule, which molecule with six carbon atoms in the ring like structure exist. After that, the structure of benzene molecule with the Graphene will be related, the fascinating two-dimensional material which flat network of interconnected benzene rings in hexagonal honeycomb lattice are arranged, from single to many atomic layers. The new bond structure, for this unusual bond structure in Graphene, is proposed. Also a new mechanism for the unclear mechanism as; how electrons always travels with same speed in Graphene, independent of applied voltage, will be presented. Second, the new mechanism presented here, has also great potential and capability for solving the essential conducting mechanism in similar unusual phenomenon, known as superconductivity. This mechanism can be especially efficient in the superconducting materials as intercalated Bilayer Graphene, where charge-density waves and bipolar supercurrent, were for the first time observed. For the both of this mechanisms the most important thing is the " stand on " point, round which atoms or molecules can frilly rotate.
Physical Review B, 2019
Carbon(C) doped hexagonal boron nitride(hBN) has been experimentally reported to be ferromagnetic at room temperature. Substitution by C in hBN has been also reported to form islands of graphene. In this work we derive a mechanistic understanding of ferromagnetism with graphene islands in hBN from first principles and mean-field Hubbard model. We find a general property, that in bipartite lattices where the sublattices differ in on-site energies, as in hBN, the ordering between local magnetic moments can be substantial and predominantly anti-ferromagnetic(AFM) if they are embedded in the same sublattice, unless dominated by Mott like inter-sublattice spin separation due to strong localization. The dominant AFM order is rooted at spin resolved spatial separation of lone pairs of nitrogen(N) and back transferred electrons on boron(B) due to Coulomb repulsion thus essentially implying a super-exchange pathway. Subsequently we propose a class of ferri-magnetically ordered inter-penetrating super-lattices of magnetic graphene islands in hBN, which can be chosen to be a ferromagnetic semiconductor or a half-metal, and retain a net non-zero magnetic moment at room temperature.
Theoretical investigation of superconductivity in graphene doped systems
2012
The compound of Ba(AlSn) from ternary superconductors exhibits the superconductivity behaviour below the temperature 2.9 K. We report the results of an ab initio study based on electronic, and detailed lattice dynamical properties as a function of pressure of superconducting material. The phonon dispersion curves along the high-symmetry directions and phonon frequencies parameters at the Brillouin zone center are computed by using density functional perturbation theory while the elastic constants are calculated in metric-tensor formulation. The Vickers hardness belonging to the compound is also evaluated clearly. The band structure, partial densities of states and Fermi surface topology are also discussed in detail. At the same time we describe the relationship between the properties determined and superconducting characteristic.