Carrier orbit coupling in stage-2 IBr graphite

Abstract

The electronic properties of the stage-2 IBr graphite intercalation compound were investigated by means of the de Haas-van Alphen (dHvA) effect. Thirty dHvA frequencies were found with the magnetic field parallel to the c-axis. These results are explained by the Fermi surface model formed by zone folding resulting from commensurate ( √ 183R26.33 • × 2 √ 3R0 • ) in-plane superlattice translations which coupled carrier orbits. The unfolded Fermi surface was the primitive two-dimensional Fermi surface of Blinowski et al for graphite intercalation compounds. By adjusting the dimensions of this Fermi surface, all the dHvA frequencies were interpreted with an accuracy of ≈5%. The Fermi radii of the unfolded Fermi surface were k 1 = 0.118 Å−1 and k 2 = 0.183 Å−1 . The dHvA frequencies (455 and 1106 T) were used to determine the band parameters γ 0 (the interaction of nearest neighbours) and γ 1 (the interaction of nearest layers) in Blinowski's theoretical band model for acceptor-type graphite intercalation compounds.

Electronic structures of HOPG and stage-2 IBr-GIC studied by angle resolved photoemission

“…Also π bands show such a shift but the dispersion curves become broader and their curves seem to be modified a little by IBr intercalation. The observed shift value is smaller than the reported values, 0.55 eV [2] and 0.79 eV [4]. Furthermore, a new flat branch appears at E B = 26 eV and it is attributed to I 5s and/or Br 4s states.…”

“…Intercalation of IBr molecules into van der Waals (vdW) gaps of graphite forms an acceptor graphite intercalation compound, IBr-GIC. Based on the Blinowskii-Rigaux (BR) band model [1], the variation of the valence π bands around the K point near the Fermi energy E F were discussed and controversial values of E F were evaluated using different band parameters; from Hall effect [2,3], E F = 0.55 eV using the hole concentration of 8×10 -20 cm -3 with band parameters γ 0 = 3.16 eV and γ 1 = 0.38 eV, while from the de Haas-van Alphen (dHvA) effect [4], E F = 0.79 eV using the dHvA frequencies of f 1 = 455 T and f 2 = 1106 T with γ 0 = 2.40 eV and γ 1 = 0.328 eV. However, much less is known about electronic states of IBr-GIC over full Brillouin zone (BZ).…”

Electron-phonon scattering in HgBr2and IBr graphite intercalation compounds

“…The x-ray diffraction and absorption spectroscopy studies [18,19] of the stage-2 IBr GIC established that the IBr molecules form a commensurate superlattice with lattice parameters of ( √ 183R26.33 • × 2 √ 3R0 • ) with respect to the graphite lattice vectors. The existence of a superlattice was also established in a study of the dHvA spectrum where the large number of dHvA frequencies was explained by the overlapping of the Fermi surfaces by the zone folding effect [10]. The formation of the superlattice is expected to have an effect on the temperature dependence of the resistivity.…”

“…The composition C 20.8 IBr was determined by the change in weight during intercalation. The stage-2 IBr GIC was characterized by (00l) x-ray diffraction as shown previously with a spectrum revealing a pure staged sample with no diffraction peaks from mixed stages [10] with a period scale I c of 10.5 Å. The stage-3 HgBr 2 GIC samples were prepared by reacting HgBr 2 with HOPG in a Br atmosphere at a pressure of 2 atm at a temperature of 200 • C for 9 weeks.…”

“…To our knowledge, a rather small amount of work on the electronic properties of the bromide GICs has been reported. The de Haas-van Alphen (dHvA) effect of the stage-2 IBr GIC has been studied to reveal a superlattice formation and zone folding at low temperature [10].…”