Magnetic properties and critical behavior of the conductivity near the M-I transition
Our studies of the resistivity and the magnetoresistance of Si:B show that the critical exponent {nu} which characteristics the approach of the zero-temperature conductivity, {sigma}(0)={sigma}{sub 0}((n/n{sub c})-1){nu}, to the metal-insulator transition is equal to 1 in almost all cases. With the possible exception of Ga:Ar, this is true for all semi-conductor-metal alloys (e.g. Ge:Au) measured to date, and for compensated doped semiconductors such as Si:(P,B), as well as uncompensated Ge:Sb. Our choice of p-type Si:B as an interesting material for study was prompted by the fact that, on the one hand, it is an uncompensated silicon based material for which {nu}={1/2} in all other cases measured to date while, on the other hand, spin-orbit effects are known to be important so that theory predicts that the critical exponent should be unity. Our measurements established that the exponent of Si:B is in fact close to {1/2} despite the strong spin-orbit scattering. From extensive measurements of the resistivity of a series of samples of n-type CdSe in the absence of a magnetic field, we reported the first experimental finding of a crossover with decreasing temperature from Mott variable range hopping, {rho}={rho}{sub 0}exp(T{sub o}/T){sup 1/4}, to a form of variable range hopping expected in the presence of a Coulomb gap'' due to electron correlations, namely {rho}={rho}{sub o}{prime}exp(T{sub o}{prime}/T){sup 1/2}.
- Research Organization:
- City Coll., New York, NY (United States). Dept. of Physics
- Sponsoring Organization:
- USDOE; USDOE, Washington, DC (United States)
- DOE Contract Number:
- FG02-84ER45153
- OSTI ID:
- 6252782
- Report Number(s):
- DOE/ER/45153-8; ON: DE92003043
- Country of Publication:
- United States
- Language:
- English
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DOPED MATERIALS
ELECTRIC CONDUCTIVITY
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BORON ADDITIONS
CADMIUM SELENIDES
ELECTRON CORRELATION
HALL EFFECT
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PROGRESS REPORT
SILICON
ULTRALOW TEMPERATURE
ALLOYS
BORON ALLOYS
CADMIUM COMPOUNDS
CHALCOGENIDES
CORRELATIONS
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360606* - Other Materials- Physical Properties- (1992-)