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Fermion space charge in narrow-band gap semiconductors, Weyl semimetals and around highly charged nuclei

Date:
-
Location:
CP179
Speaker(s) / Presenter(s):
Eugene B. Kolomeisky (University of Virginia)
The field of charged impurities in narrow-band gap semiconductors and Weyl semimetals can create electron-hole pairs when the total charge Ze of the impurity exceeds a value Z_{c}e.  Particles of one charge escape to infinity, leaving a screening space charge.  The result is that the observable dimensionless impurity charge Q_{infinity} is less than Z but greater than Z_{c}.  There is a corresponding effect for nuclei with Z >Z_{c} \approx 170, however in the condensed matter setting we find Z_{c} to be about 10.  Thomas-Fermi theory indicates that Q_{\infinity} = 0 for the Weyl semimetal, but we argue that this is a defect of the theory. For the case of a highly-charged recombination center in a narrow band-gap semiconductor (or of a supercharged nucleus),  the observable charge takes on a nearly universal value.  In Weyl semimetals the observable charge takes on the universal value Q_{infinity} = Z_{c} set by the reciprocal of material's fine structure constant.