Manifestations of Strange Metallicity in Inelastic Neutron Studies

Abstract

Emergence of an orbital-selective Mott phase (OSMP) found in multi-band correlated systems leads to a non-perturbative obliteration of the Landau Fermi liquid in favor of a novel metallic state exhibiting anomalous infra-red (branch-cut) continuum features in one-and two-particle responses. We use a combination of (1) dynamical mean-field theory (DMFT) using the continuous-timequantum Monte-Carlo (CTQMC) solver for a two-band Hubbard model and (2) analytic arguments from an effective bosonized description to investigate strange metal features in inelastic neutron scattering studies for cuprates. Specifically, restricting our attention to symmetry-unbroken metallic phase, we study how emergence of an OSMP leads to qualitatively novel features in (i) the dynamical spin and charge susceptibilities, and (ii) phonon response in the strange metal, in detail. Extinction of the Landau quasiparticle pole in the one-electron propagator in the OSMP mirrors the emergence of critical liquid-like features in the dynamical spin response. This novel finding also underpins truly anomalous features in phonon dynamics, which we investigate by coupling half-breathing phonons in the specific context of cuprates to such a multi-electronic continuum. We find good understanding of various anomalies encountered in experimental inelastic neutron scattering studies in the near-optimally doped cuprates. We also extend these results in a phenomenological way to argue how modification of phonon spectra in underdoped cuprates can be reconciled with proposals for a nematic-plus-d-wave charge modulation order in the pseudogap state. We also study the issue of the dominant "pair glue" contributions to superconductivity, allowing us to interpret recent pump-probe results within a strange metal scenario.

The Iso-electronic Series $Ca_{2-x}Sr_{x}RuO_{4}$: Structural Distortion, Effective Dimensionality, Spin Fluctuations and Quantum Criticality

“…This could well be a critical end point (T = 0, x = 0.5) as there is no experimentally reported structural transition either suppressing or facilitating the critical ferromagnetic fluctuation at this point 43 . The orbital selective pseudogapped 44 nature of the density of states and non-Fermi-liquid self-energy response also act as supportive informations for the observation of quantum criticality, which has been rigorously shown to be existing in different contexts [45][46][47][48] in literature, with similar single-particle responses.…”