Condensed Matter Seminar: Israel Klich, University of Virginia - “A novel quantum phase transition from area law to massive entanglement”

How much entanglement can the ground sate of a physical system governed by strictly local interactions support? Most known examples obey the so-called “area law”: the entropy of a region scales as it’s boundary, violations of this behavior for critical systems are typically logarithmic. Here, I describe a family of spin chains with a massively entangled ground state with simple nearest-neighbor interactions. In this chain, the entropy scales with the volume and breaks all previous records for entanglement per spin generated by local Hamiltonians. The ground state is, unique, frustration free and exactly solvable and exhibits an explicit quantum phase transition from area law to the massively entangled state. The chain provides an extreme example of a 1D quantum critical system that is not described in terms of a conformal field theory. I will also describe a tensor network representation of the state, results on the exotic scaling of the spectral gap in the system, and remark on outstanding questions.