Quantum Critical Phase and Lifshitz Transition in an Extended Periodic Anderson Model

We study the quantum phase transition in $f$-electron systems as a quantum Lifshitz transition driven by selective Mott localization in a realistic extended Anderson lattice model. Using DMFT, we find that a quantum critical {\it phase} with anomalous $\omega/T$ scaling separates a heavy Landau-Fermi liquid from ordered phase(s). Fermi surface reconstruction occurs via the interplay between, and penetration of the Green function zeros to the poles, leading to violation of Luttinger's theorem in the selective-Mott phase . We show how this naturally leads to scale-invariant responses in transport. Our work is represents a specific (DMFT) realization of the hidden-FL and FL$^{*}$ theories, and holds promise for study of "strange" metal phases in quantum matter.Comment: 8 pages,5 figure

Preformed excitonic liquid route to a charge density wave in 2H-TaSe2_2

Recent experiments on 2H-TaSe$_2$ contradict the long-held view of the charge density wave arising from a nested band structure. An intrinsically strong coupling view, involving a charge density wave state arising as a Bose condensation of preformed excitons emerges as an attractive, albeit scantily investigated alternative. Using local density approximation plus multiorbital dynamic mean-field theory, we show that this scenario agrees with a variety of normal state data for 2H-TaSe$_{2}$. Based thereupon, the ordered states in a subset of dichalcogenides should be viewed as instabilities of a correlated, preformed excitonic liquid.Comment: 4 pages,8 figure