Optical Conductivity in the Cuprates from Holography and Unparticles

Speaker: Philip Phillips, University of Illinois at Urbana-Champaign

When: October 30, 2015 (Fri), 12:00PM to 01:00PM (add to my calendar)
Location: SCI 352

This event is part of the Biophysics/Condensed Matter Seminar Series.

Two features of the optical conductivity in the cuprates that remain unresolved are the 1) power-law scaling with frequency in the mid-infrared and 2) a violation of the f-sum rule. So befuddling is the former that even high-energy theorists have written papers on the puzzling $\omega^{-2/3}$ scaling law in the cuprates. The key claim here is that the observed power law is a universal consequence of gravity in the presence of translational symmetry breaking. I will explain this claim and report on a calculation tests this claim. I will show that the general claim is not true. As an alternative, I will show how unparticles or a scale invariant sector in the mid-infrared can account for the experimentally observed power law and a violation of the f-sum rule. I will close by showing how a recent mapping between unparticles and massive gravity offers a window into how gravity might underlie the physics of the cuprates.