7 research outputs found
Pseudogap temperature as a Widom line in doped Mott insulators
The pseudogap refers to an enigmatic state of matter with unusual physical
properties found below a characteristic temperature in hole-doped
high-temperature superconductors. Determining is critical for
understanding this state. Here we study the simplest model of correlated
electron systems, the Hubbard model, with cluster dynamical mean-field theory
to find out whether the pseudogap can occur solely because of strong coupling
physics and short nonlocal correlations. We find that the pseudogap
characteristic temperature is a sharp crossover between different
dynamical regimes along a line of thermodynamic anomalies that appears above a
first-order phase transition, the Widom line. The Widom line emanating from the
critical endpoint of a first-order transition is thus the organizing principle
for the pseudogap phase diagram of the cuprates. No additional broken symmetry
is necessary to explain the phenomenon. Broken symmetry states appear in the
pseudogap and not the other way around.Comment: 6 pages, 4 figures and supplementary information; published versio
Phase diagram and single-particle spectrum of CuO layers within a variational cluster approach to the 3-band Hubbard model
We carry out a detailed numerical study of the three-band Hubbard model in
the underdoped region both in the hole- as well as in the electron-doped case
by means of the variational cluster approach. Both the phase diagram and the
low-energy single-particle spectrum are very similar to recent results for the
single-band Hubbard model with next-nearest-neighbor hoppings. In particular,
we obtain a mixed antiferromagnetic+superconducting phase at low doping with a
first-order transition to a pure superconducting phase accompanied by phase
separation. In the single-particle spectrum a clear Zhang-Rice singlet band
with an incoherent and a coherent part can be seen, in which holes enter upon
doping around . The latter is very similar to the coherent
quasi-particle band crossing the Fermi surface in the single-band model. Doped
electrons go instead into the upper Hubbard band, first filling the regions of
the Brillouin zone around . This fact can be related to the enhanced
robustness of the antiferromagnetic phase as a function of electron doping
compared to hole doping.Comment: 14 pages, 15 eps figure
Optical weights and waterfalls in doped charge-transfer insulators: A local density approximation and dynamical mean-field theory study of La2−xSrxCuO4
We use the Local Density Approximation in combination with the Dynamical Mean
Field Theory to investigate intermediate energy properties of the copper
oxides. We identify coherent and incoherent spectral features that results from
doping a charge transfer insulator, namely quasiparticles, Zhang-Rice singlet
band, and the upper and lower Hubbard bands. Angle resolving these features, we
identify a \emphasize{waterfall} like feature, between the quasiparticle part
and the incoherent part of the Zhang-Rice band. We investigate the assymetry
between particle and hole doping. On the hole doped side, there is a very rapid
transfer of spectral weight upon doping in the one particle spectra. The
optical spectral weight increases superlinearly on the hole doped side in
agreement with experiments.Comment: 4 page
Apical oxygens and correlation strength in electron-and hole-doped copper oxides
We use the Local Density Approximation in combination with the Dynamical Mean
Field Theory to carry out a comparative investigation of a typical electron
doped and a typical hole doped copper oxide, NCCO and LSCO respectively. The
parent compounds of both materials are strongly correlated electron systems in
the vicinity of the metal to charge transfer insulator transition. In NCCO the
magnetic long range order is essential to open a charge transfer gap, while
Mott physics is responsible for the gap in LSCO. We highlights the role of the
apical oxygens in determining the strength of the correlations and obtaining
overall good agreement between theory and several experimentally determined
quantities. Results for optical conductivity, polarized X-ray absorption and
angle resolved photoemission are presented and compared with experiments.Comment: submitted to PR
Scaling of the transition temperature of hole-doped cuprate superconductors with the charge-transfer energy
We use first-principles calculations to extract two essential microscopic parameters, the charge-transfer energy and the inter-cell oxygen-oxygen hopping, which correlate with the maximum superconducting transition temperature Tc,max across the cuprates. We explore the superconducting state in the three-band model of the copper-oxygen planes using cluster Dynamical Mean-Field Theory. We find that the variation in the charge-transfer energy largely accounts for the empirical trend in Tc,max, resolving a long-standing contradiction with theoretical calculations