On Magnetic Impurities in Gapless Fermi Systems
نویسنده
چکیده
In ordinary metals, antiferromagnetic exchange between conduction electrons and a magnetic impurity leads to screening of the impurity spin below the Kondo temperature, TK . In systems such as semimetals, small-gap semiconductors and unconventional superconductors, a reduction in available conduction states near the chemical potential can greatly depress TK . The behavior of an Anderson impurity in a model with a power-law density of states, N(ǫ) ∼ |ǫ|, r > 0, for |ǫ| < ∆, where ∆ ≪ D, is studied using the non-crossing approximation. The transition from the Kondo singlet to the magnetic ground state can be seen in the behavior of the impurity magnetic susceptibility χ. The product Tχ saturates at a finite value at low temperature for coupling smaller than the critical one. For sufficiently large coupling Tχ → 0, as T → 0, indicating complete screening of the impurity spin. Typeset using REVTEX
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تاریخ انتشار 1996