The effect of a weak magnetic field on the variable-range hopping regime in GaAs

ABSTRACTWe review the origins of the magnetoresistance in granular metals with emphasis on the quantum coherence effects arising from the interference of electrons traveling by different paths. We discuss the maximum in the magnetoresistance expected from scaling arguments and observed in granular aluminum. Two theories of the magnetoresistance in the variable range hopping regime, one based on the magnetic-field induced shift of the mobility edge and the other dealing with ‘directed’ hopping, are compared with experiments.

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HOPPING TRANSPORT ALONG A POTENTIAL WALL: OSCILLATIONS OF THE MAGNETORESISTANCE IN A PARALLEL FIELD

International Journal of Modern Physics B ◽

10.1142/s0217979293003243 ◽

1993 ◽

Vol 07 (18) ◽

pp. 3313-3326

Author(s):

M.E. RAIKH ◽

T.V. SHAHBAZYAN

Keyword(s):

Magnetic Field ◽

Pronounced Effect ◽

Variable Range Hopping ◽

General Increase ◽

Hopping Transport ◽

Variable Range ◽

Parallel Field ◽

Shrinkage Effect ◽

2D System ◽

Localized Electrons

We study the variable-range-hopping magnetoresistance of a 2D system of localized electrons in the presence of a boundary parallel to the plane of the 2D electrons. In a magnetic field B parallel to the plane, the magnetoresistance oscillates with B if the distance between the plane and the boundary is not too large. These oscillations result from the interference of the amplitude of the in-plane tunneling path with the amplitude of the path reflected by the boundary. We show that the orbital shrinkage effect, altering differently both amplitudes, strongly enhances the interference. At the same time, the amplitude of oscillations appears to be small compared to the general increase in the resistance caused by the orbital shrinkage. The most pronounced effect of the interference can be seen in the differential magnetoresistance R−1(B)∂R(B)/∂B, which we analyze numerically.

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Magnetic field and temperature dependences of the electrical resistance of onion structure carbon

Siberian Journal of Physics ◽

10.54362/1818-7919-2008-3-2-95-98 ◽

2010 ◽

Vol 3 (2) ◽

pp. 95-98

Author(s):

Evgeny N. Tkachev ◽

Anatoliy I. Romanenko ◽

Olga B. Anikeeva ◽

Timofey I. Buryakov ◽

Kamil R. Zhdanov ◽

...

Keyword(s):

Magnetic Field ◽

Physical Properties ◽

Fermi Level ◽

Density Of States ◽

Electrical Resistance ◽

Variable Range Hopping ◽

Hopping Conductivity ◽

Variable Range ◽

Localization Radius ◽

Temperature Dependences

In this paper electro physical properties of samples of onion-like carbon have been investigated. Samples have been synthesized by method of thermal graphitization of nanodiamonds. 1D Mott variable-range hopping conductivity has been observed for temperature dependences of resistance of nanoonions volume samples at temperature range 4.2 K – 300 K. Also second-degree increase of positive magnetoresistance up to 6 tesla has been revealed. Some coefficients such as localization radius a, density of states on Fermi level N(EF) have been estimated.

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