Magnetic properties and critical behavior of the conductivity near the M-I transition

Technical Report · Fri Nov 01 04:00:00 EST 1991

DOI:https://doi.org/10.2172/6252782· OSTI ID:6252782

Sarachik, M

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: DOE; 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

Related Subjects

36 MATERIALS SCIENCE
360606* -- Other Materials-- Physical Properties-- (1992-)
ALLOYS
BORON ADDITIONS
BORON ALLOYS
CADMIUM COMPOUNDS
CADMIUM SELENIDES
CHALCOGENIDES
CORRELATIONS
COUPLING
DOCUMENT TYPES
DOPED MATERIALS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELECTRON CORRELATION
ELEMENTS
HALL EFFECT
INTERMEDIATE COUPLING
L-S COUPLING
MAGNETORESISTANCE
MATERIALS
PHYSICAL PROPERTIES
PROGRESS REPORT
SELENIDES
SELENIUM COMPOUNDS
SEMIMETALS
SILICON
ULTRALOW TEMPERATURE