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Colloquia
Colloquium
Friday, October 17, 2014
3:30 PM
Physics Building, Room 204

Genya Kolomeisky
[Host: Dinko Pocanic]
University of Virginia
"Fermion space charge in narrowband gap semiconductors, Weyl semimetals and around highly charged nuclei"
Slideshow (PDF)

ABSTRACT:
The field of charged impurities in narrowband gap semiconductors and Weyl semimetals can create electronhole pairs when the total charge $Ze$ of the impurity exceeds a value $Z_{c}e.$ The particles of one charge escape to infinity, leaving a screening space charge. The result is that the observable dimensionless impurity charge $Q_{\infty}$ 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 $Z_{c} \simeq 10$. ThomasFermi theory indicates that $Q_{\infty} = 0$ for the Weyl semimetal, but we argue that this is a defect of the theory. For the case of a highlycharged recombination center in a narrow bandgap 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 $Q_{\infty} = Z_{c}$ set by the reciprocal of material's fine structure constant.

SLIDESHOW:




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