Zenith Grant Awardee

Dr. Subir Sachdev

Harvard University

Project Title

Quantum Criticality and Black Holes

Project Summary

This project explores a new connection between two seemingly disconnected fields of physics. One field studies the electrical and thermal properties of crystals of technologically important materials that are being measured in laboratories around the world. Their properties are determined by the motion of electrons in the crystal, which are controlled by the principles of quantum mechanics. Often the electrons exhibit new phases of collective behavior, and the transitions between these phases have led to especially difficult problems in quantum theory. The second field uses Einstein's theory of gravity to understand very heavy stars known as black holes. Recent developments in string theory have led to an improvement in our understanding of the quantum theory of black holes. More stunningly, these developments have shown that this quantum theory of black holes is closely connected to the theory of the quantum phase transitions of electrons in crystals. Importantly, easy questions in one field usually map to difficult questions in the other. This complementary relationship will surely lead to new insights in both fields. The history of physics is replete with examples of foundational insights discovered by paying attention to seemingly mundane experimental facts, and we hope to continue that tradition.

Technical Abstract

This project explores connections between the theory of quantum criticality in condensed matter systems and the quantum theory of black holes. This connection relies on the gauge/gravity duality, which has been shown to relate to several interesting quantum critical points found in correlated electron systems. This duality motivates several new approaches to analyzing the observable properties of the cuprate superconductors, layers of graphene, and magnets near quantum critical points. Experimental comparisons have already been performed near the superfluid-insulator transition, and these will be extended to a much wider variety of transitions, and to a larger range of temperatures. Conversely, insights from the condensed matter systems have informed the discovery of new Higgs phases around black holes. These also have important implications for the superfluid-insulator transition, which will be studied. We thus see that there is an unprecedented relation between deep and foundational questions on the quantum theory of black holes, and some experimentally measureable properties of transition metal compounds. The history of physics is replete with examples of foundational insights discovered by paying attention to seemingly mundane experimental facts, and we hope to continue that tradition.