Hopping conductivity of carbynes modified under high pressures and temperatures: Galvanomagnetic and thermoelectric properties |
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Authors: | S V Demishev A Pronin V V Glushkov N E Sluchanko N A Samarin M V Kondrin G Lyapin V V Brazhkin T D Varfolomeeva S V Popova |
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Institution: | (1) Institute of General Physics, Russian Academy of Sciences, ul. Vavilova 38, Moscow, 119991, Russia;(2) Institute of High-Pressure Physics, Russian Academy of Sciences, Troitsk, Moscow oblast, 142190, Russia |
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Abstract: | The conductivity, thermopower, and magnetoresistance of carbynes structurally modified by heating under a high pressure are investigated in the temperature range 1.8–300 K in a magnetic field up to 70 kOe. It is shown that an increase in the synthesis temperature under pressure leads to a transition from 1D hopping conductivity to 2D and then to 3D hopping conductivity. An analysis of transport data at T ≤ 40 K makes it possible to determine the localization radius a ~ (56?140) Å of the wave function and to estimate the density of localized states g(E F) for various dimensions d of space: g(E F) ≈ 5.8 × 107 eV?1 cm?1 (d=1), g(E F) ≈5×1014 eV?1 cm ?2 (d=2), and g(E F)≈1.1×1021 eV?1 cm?3 (d=3). A model for hopping conductivity and structure of carbynes is proposed on the basis of clusterization of sp 2 bonds in the carbyne matrix on the nanometer scale. |
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