ICTS

The quasiparticle concept is the foundation of our understanding of the dynamics of quantum many-body systems. It originated in the theory of metals, which have electron-like quasiparticles; but it is also useful in more exotic states like those found in fractional quantum Hall systems. However, many modern materials exhibit a `strange metal' phase to which the quasiparticle picture does not apply, and developing its theory remains one of the important challenges in condensed matter physics. They SYK models are the simplest known quantum many-body systems without quasiparticle excitations: I will describe recent progress in extending these solvable models to a semi-realistic theory of strange metals. The SYK models also have a dual description as black holes in a curved spacetime with an emergent spatial direction, and the black hole connection has proved useful in the theoretical development.