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Condensed Matter Seminar: Low energy electrodynamics of the missing superconducting electrons in overdoped cuprates

Event Type
Seminar/Symposium
Sponsor
Physics - Condensed Matter
Location
190 ESB
Date
Dec 6, 2019   1:00 pm  
Speaker
Fahad Mahmood, University of Illinois at Urbana-Champaign
Views
54
Originating Calendar
Physics - Condensed Matter Seminar

Overdoped high-temperature cuprate superconductors have been widely believed to be described by the physics of d-wave BCS-like superconductivity. This view was strongly challenged by recent measurements of the superfluid density which found that even as the carrier concentration increases on the overdoped side, the superfluid density decreases – Cooper pairs seem to be ‘missing’ from the condensate. In this talk, I will discuss how we use time-domain THz spectroscopy combined with kHz range mutual inductance measurements on overdoped La2-xSrxCuO4 to directly locate the ‘missing’ carriers and discover that they display an exceedingly large metal-like response even deep into the superconducting state. I will discuss various explanations/consequences for this behavior including quantum phase fluctuations as the critical doping is approached. I will also present some recent results using non-linear THz spectroscopy that potentially highlight an anomalously large third-order susceptibility above the superconducting Tc. These results challenge the conventional view of describing the normal state of overdoped cuprates as a weakly interacting Fermi liquid.

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