Excited-State Quantum Phase Transitions in Bosonic Lattice Systems

Abstract

Concentrating on bosonic lattice systems, we ask whether and how Excited State Quantum Phase Transition (ESQPT) singularities occur in condensed matter systems with ground state QPTs. We study in particular the spectral singularities above the ground-state phase diagram of the boson Hubbard model. As a general prerequisite, we point out the analogy between ESQPTs and van Hove singularities (vHss).

Comments: 3 pages, 2 figures, to appear in AIP Conference Proceedings, Symmetries And Order: Algebraic Methods In Many Body Systems, In honor of Professor Francesco Iachello on the occasion of his retirement, October 5-6, 2018 at Yale University (v2 minor reformulations)