Electrical Conductivities of Natural Graphite Crystals

Abstract

The principal electrical conductivities (<r a in the basal plane and <r c perpendicular to the basal plane) of graphite crystals isolated from several North American marbles were studied. By means of measurements of potential distributions on the surfaces of crystals carrying electric current, it was conclusively shown that (r a /<rc for these crystals is about several hundred at room temperature. By direct measurement a a was found to be (2.6±0.2)X10 4 (ohm cm)" 1 and a c to vary from 150 to 230 (ohm cm) -1 (±20 percent) at room temperature. Below room temperature it was found for two crystals that <r 0 increased slowly to liquid nitrogen temperatures, then followed a T~x law to about 15°K, and again slowly increased in the region 15°K to 4.2°K. Two other crystals for which cr c was measured at low temperatures did not behave alike. For both, Go decreased as the temperature was lowered, reached a minimum above liquid nitrogen temperatures, and then started increasing, the one showing a T" 1 behavior, the other increasing more slowly. For both, the rate of increase declined markedly in the region 15°K to 4.2 °K.

Approaching ultrastrong coupling in transmon circuit QED using a high-impedance resonator

“…The ohmic losses in the graphite can also not explain this high dissipation. From the bulk conductivity of graphite, we find that the resistance of our 50 nm thick flake is 7 / [38]. Simulating the effect of a 7 resistance at the appropriate position in the qubits capacitance network using QUCS [39] reveals that this has a negligible contribution of 200 kHz to the total transmon linewidth.…”

High Pressure and Superconductivity: Intercalated Graphite Cac6 as a Model System

“…The ambient pressure results (see also Gauzzi et al, 2007) yield low values of room temperature and residual resistivities, ρ 300 K = 46 μΩ cm and ρ 0 = 0.8 μΩ cm, respectively, and a large residual resistivity ratio, RRR = ρ 300 K /ρ 0 = 58. The T-dependence gradually approaches a linear behavior at high T. This dependence is very different from that of graphite, although the ρ 300 K value is similar (Klein et al, 1962;Primak and Fuchs, 1954). First, in graphite, RRR is much smaller and ~15 even in best quality samples (Primak and Fuchs, 1954;Soule, 1958).…”

Conductivity of multiwall carbon nanotubes: Role of multiple shells and defects

“…perpendicular to the layers spreads from 4.3 10 −5 Ωm to 6.7 10 −5 Ωm [112,113], depending strongly on the quality of the crystal. Even highly oriented pyrolytic graphite (HOPG) shows a volume resistivity up to 100 times higher along the c-axis than single crystals [113].…”