Evidence of hot and cold spots on the Fermi surface of LiFeAs

Abstract

Angle-resolved photoemission spectroscopy (ARPES) is used to study the energy and momentum dependence of the inelastic scattering rates and the mass renormalization of charge carriers in LiFeAs at several high symmetry points in the Brillouin zone. A strong and linear-in-energy scattering rate is observed for sections of the Fermi surface having predominantly Fe 3d xy/yz orbital character on the inner hole and on electron pockets. We assign them to hot spots with marginal Fermi liquid character inducing high antiferromagnetic and pairing susceptibilities. The outer hole pocket, with Fe 3dxy orbital character, has a reduced but still linear in energy scattering rate. Finally, we assign sections on the middle hole pockets with Fe 3dxz,yz orbital character and on the electron pockets with Fe 3dxy orbital character to cold spots because there we observe a quadratic-in-energy scattering rate with Fermi-liquid behavior. These cold spots prevail the transport properties. Our results indicate a strong momentum dependence of the scattering rates. We also have indications that the scattering rates in correlated systems are fundamentally different from those in non-correlated materials because in the former the Pauli principle is not operative. We compare our results for the scattering rates with combined density functional plus dynamical mean-field theory calculations. The work provides a generic microscopic understanding of macroscopic properties of multiorbital unconventional superconductors. arXiv:1807.11220v2 [cond-mat.supr-con]

Theory of two-fluid metallicity in superconducting FeSe at high pressure

“…We predict that similar features as in Fig. 4 would be seen in scattering rates τ −1 (ω) Im (ω) [37], and future angle-resolved photoemission spectroscopy (ARPES) studies are called for to corroborate our prediction. Moreover, since in DMFT the self-energy is momentum independent, the quasiparticle residue Z directly yields the effective electron mass enhancement [38]…”

Effect of Nonlocal Correlations on the Electronic Structure of LiFeAs

“…very diffuse at the Fermi level due to incoherent scattering processes, leading to a significant reduction of the lifetime of quasi-particle excitations. This manifests in a broad Fermi surface feature very similar to the one observed in ARPES [24][25][26]28,30 . The maximum of the spectral function of the two inner hole pockets at Γ is shifted basically on top of the Fermi level but retains significant spectral weight at higher and lower binding energies.…”

Pressure-induced orbital-selective metal from the Mott insulator BaFe2Se3

“…Since the correlated Fermi sea expected to be seen in future experiments at pressures close to 12.7 GPa can be described in terms of well-defined quasiparticles, it is instructive to look at the orbital-resolved scattering rates a (ω) = −2Z a (ω)Im a (ω) [52] as a function of binding energy derived from LDA+DMFT for U = 4.7 eV. Here…”