Date : February 28, 2023, 16:00 CET
Eric Mefford (University of Victoria)
Zero sound and higher-form symmetries in compressible holographic phases
Abstract: Certain holographic states of matter with a global U(1) symmetry support a sound mode at zero temperature, caused neither by spontaneous symmetry breaking of the global U(1) nor by the emergence of a Fermi surface in the infrared. In this talk, I will present recent work that illustrates that such a mode is also found in zero density holographic quantum critical states. I will argue that the appearance of a zero temperature sound mode is the consequence of a mixed ‘t Hooft anomaly between the global U(1) symmetry and an emergent higher-form symmetry. At non-zero temperatures, the presence of a black hole horizon weakly breaks the emergent symmetry and gaps the collective mode, giving rise to a sharp Drude-like peak in the electric conductivity. Time permitting, I will present evidence that the same physics emerges in certain finite density holographic quantum critical states at low temperatures.