Metal-insulator transition of isotopically enriched neutron-transmutation-doped {sup 70}Ge:Ga in magnetic fields
- Department of Applied Physics and Physico-Informatics, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, (Japan)
- Department of Applied Physics and Physico-Informatics, Keio University and PRESTO-JST, 3-14-1, Hiyoshi, Kohoku-ku 223-8522, (Japan)
- Institute of Physics, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571, (Japan)
- Lawrence Berkeley National Laboratory and University of California at Berkeley, Berkeley, California 94720 (United States)
We have investigated the temperature dependence of the electrical conductivity {sigma}(N,B,T) of nominally uncompensated, neutron-transmutation-doped {sup 70}Ge:Ga samples in magnetic fields up to B=8 T at low temperatures (T=0.05-0.5 K). In our earlier studies at B=0, the critical exponent {mu}=0.5 defined by {sigma}(N,0,0){proportional_to}(N-N{sub c}){sup {mu}} has been determined for the same series of {sup 70}Ge:Ga samples with the doping concentration N ranging from 1.861x10{sup 17} cm{sup -3} to 2.434x10{sup 17} cm{sup -3}. In magnetic fields, the motion of carriers loses time-reversal symmetry, the universality class may change and with it the value of {mu}. In this work, we show that magnetic fields indeed affect the value of {mu} ({mu} changes from 0.5 at B=0 to 1.1 at B{>=}4 T). The same exponent {mu}{sup '}=1.1 is also found in the magnetic-field-induced MIT for three different {sup 70}Ge: Ga samples, i.e., {sigma}(N,B,0){proportional_to}[B{sub c}(N)-B]{sup {mu}}{sup '} where B{sub c}(N) is the concentration-dependent critical magnetic induction. We show that {sigma}(N,B,0) obeys a simple scaling rule on the (N,B) plane. Based on this finding, we derive from a simple mathematical argument that {mu}={mu}{sup '} as has been observed in our experiment. (c) 1999 The American Physical Society.
- OSTI ID:
- 20217821
- Journal Information:
- Physical Review. B, Condensed Matter and Materials Physics, Vol. 60, Issue 23; Other Information: PBD: 15 Dec 1999; ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- English
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