Variable range cotunneling and conductivity of a granular metal
M. V. Feigel'man, A. S. Ioselevich1)
L. D. Landau Institute for Theoretical Physics RAS, 119334 Moscow, Russia
PACS: 73.23.Hk, 73.43.Qt, 73.63.-b
The Efros-Shklovskii (E-S) law for the conductivity of granular
metals is interpreted as a result of a variable range cotunneling process.
The cotunneling between distant resonant grains is predominantly elastic at
low , while it is inelastic (i.e., accompanied by creation of
electron-hole pairs on a string of intermediate non-resonant grains) at . The corresponding E-S temperature TES in the latter case is
slightly (logarithmically) T-dependent. The magnetoresistance in
the two cases is different: it may be relatively strong and
negative at , while at T>Tc it is suppressed due to
inelastic processes which destroy the interference.