E. Perepelitsky | Searcharxiv

arXiv2018

Band-edge quasiparticles from electron phonon coupling and resistivity saturation

We address the problem of resistivity saturation observed in materials such as the A-15 compounds. To do so, we calculate the resistivity for the Hubbard-Holstein model in infinite spatial dimensions to second order in on-site repulsion $U\leq D$ and to first order in (dimensionless) electron-phonon coupling strength $λ\leq0.5$, where $D$ is the half-bandwidth. We identify a unique mechanism to obtain two parallel quantum conducting channels: low-energy and band-edge high-energy quasi-particles. We identify the source of the hitherto unremarked high-energy quasi-particles as a positive slope in the frequency-dependence of the real part of the electron self-energy. In the presence of phonons, the self-energy grows linearly with the temperature at high-$T$, causing the resistivity to saturate. As $U$ is increased, the saturation temperature is pushed to higher values, offering a mechanism by which electron-correlations destroy saturation.

cond-mat.str-el↗

arXiv2013

Extremely correlated Fermi liquid theory meets Dynamical mean-field theory: Analytical insights into the doping-driven Mott transition

We consider a doped Mott insulator in the large dimensionality limit within both the recently developed Extremely Correlated Fermi Liquid (ECFL) theory and the Dynamical Mean-Field Theory (DMFT). We show that the general structure of the ECFL sheds light on the rich frequency-dependence of the DMFT self-energy. Using the leading Fermi-liquid form of the two key auxiliary functions introduced in the ECFL theory, we obtain an analytical ansatz which provides a good quantitative description of the DMFT self-energy down to hole doping level 0.2. In particular, the deviation from Fermi-liquid behavior and the corresponding particle-hole asymmetry developing at a low energy scale are well reproduced by this ansatz. The DMFT being exact at large dimensionality, our study also provides a benchmark of the ECFL in this limit. We find that the main features of the self-energy and spectral line-shape are well reproduced by the ECFL calculations in the O(λ^2) `minimal scheme', for not too low doping level >0.3. The DMFT calculations reported here are performed using a state-of-the-art numerical renormalization-group impurity solver, which yields accurate results down to an unprecedentedly small doping level 0.001.

cond-mat.str-el↗