Gutzwiller Charge Phase Diagram of Cuprates, including Electron-Phonon Coupling Effects

Besides significant electronic correlations, high-temperature superconductors also show a strong coupling of electrons to a number of lattice modes. Combined with the experimental detection of electronic inhomogeneities and ordering phenomena in many high-T_c compounds, these features raise the question as to what extent phonons are involved in the associated instabilities. Here we address this problem based on the Hubbard model including a coupling to phonons in order to capture several salient features of the phase diagram of hole-doped cuprates. Charge degrees of freedom, which are suppressed by the large Hubbard U near half-filling, are found to become active at a fairly low doping level. We find that possible charge order is mainly driven by Fermi surface nesting, with competition between a near-(pi,pi) order at low doping and antinodal nesting at higher doping, very similar to the momentum structure of magnetic fluctuations. The resulting nesting vectors are generally consistent with photoemission and tunneling observations, evidence for charge density wave (CDW) order in YBa_2Cu_3O_{7-delta} including Kohn anomalies, and suggestions of competition between one- and two-q-vector nesting.Comment: This is a revised version of arXiv:1207.5715. 25 pages, 5 figures, plus Supplement [7 pages, 7 figures], available as a pdf [click on other, then Download Source, & extract pdf file from zip] Manuscript is under consideration at the NJ

Temperature dependence of the collective mode and its influence on the band splitting in bilayer cuprates

The recently observed bilayer splitting in high-T$_c$ cuprates is analyzed within a model where the charge carriers are coupled to a phenomenological bosonic spectrum which interpolates between the marginal Fermi liquid structure and collective mode type behavior as a function of temperature. We argue that the origin of the collective mode is probably associated with dynamic incommensurate charge density waves. Moreover it is shown that the resulting temperature dependence of the self-energy $\Sigma$ is in good agreement with $\Sigma$ as extracted from angle-resolved photoemission data.Comment: 6 pages, 4 figures, accepted for PR

Phonon renormalization from local and transitive electron-lattice couplings in strongly correlated systems

Within the time-dependent Gutzwiller approximation (TDGA) applied to Holstein- and SSH-Hubbard models we study the influence of electron correlations on the phonon self-energy. For the local Holstein coupling we find that the phonon frequency renormalization gets weakened upon increasing the onsite interaction $U$ for all momenta. In contrast, correlations can enhance the phonon frequency shift for small wave-vectors in the SSH-Hubbard model. Moreover the TDGA applied to the latter model provides a mechanism which leads to phonon frequency corrections at intermediate momenta due to the coupling with double occupancy fluctuations. Both models display a shift of the nesting-induced to a $q=0$ instability when the onsite interaction becomes sufficiently strong and thus establishing phase separation as a generic phenomenon of strongly correlated electron-phonon coupled systems.Comment: 14 pages, 11 figure

Gutzwiller Magnetic Phase Diagram of the Cuprates

A general constructive procedure is presented for analyzing magnetic instabilities in two-dimensional materials, in terms of [predominantly] double nesting, and applied to Hartree-Fock HF+RPA and Gutzwiller approximation GA+RPA calculations of the Hubbard model. Applied to the cuprates, it is found that competing magnetic interactions are present only for hole doping, between half filling and the Van Hove singularity. While HF+RPA instabilities are present at all dopings (for sufficiently large Hubbard U), in a Gutzwiller approximation they are restricted to a doping range close to the range of relevance for the physical cuprates. The same model would hold for charge instabilities, except that the interaction is more likely to be q-dependent.Comment: PRB, 9 eps figures, revtex; http://link.aps.org/doi/10.1103/PhysRevB.81.01450

Sapphic Modernists - Re-visiting Elizabeth McCausland and Berenice Abbott’s Changing New York

Within our research of female/sapphic collaborations of Modernity, a perpetual process of ‘erasure’ or the ‘writing out of art history’ of female collaborators is exposed. One such example is evident through analysis of the 1939 publication of Berenice Abbott’s photographs in Changing New York which has been acknowledged as a key contribution to urban photographic history. Little or nothing is known of the fact that all of the original captions for Changing New York were deemed not fit for publication and that the innovative spatial text-image design devised by Berenice Abbott and Elizabeth McCausland was rejected. Instead the publishers insisted on a very conservative approach to design and the blandness of the published captions read activate Berenice Abbott’s photographs much like a guide book to the city. We found the complete set of original captions to the book, written by Elizabeth McCausland, a communist and socially engaged journalist and long-time partner of Berenice Abbott. These highly critical texts act to place the photographs directly into the larger political and social context of the 1930s Depression in USA. The original attempt and idea for the book by Abbott and McCausland was intended to acknowledge both formats, text and photography, as equal in terms of activating meaning production and/or tools for critical reflection. The book was intended as a critical reflection on the harrowing social conditions and inequalities of the 1930s in New York City

Vortex, skyrmion and elliptical domain wall textures in the two-dimensional Hubbard model

The spin and charge texture around doped holes in the two-dimensional Hubbard model is calculated within an unrestricted spin rotational invariant slave-boson approach. In the first part we examine in detail the spin structure around two holes doped in the half-filled system where we have studied cluster sizes up to 10 x 10. It turns out that the most stable configuration corresponds to a vortex-antivortex pair which has lower energy than the Neel-type bipolaron even when one takes the far field contribution into account. We also obtain skyrmions as local minima of the energy functional but with higher total energy than the vortex solutions. Additionally we have investigated the stability of elliptical domain walls for commensurate hole concentrations. We find that (i) these phases correspond to local minima of the energy functional only in case of partially filled walls, (ii) elliptical domain walls are only stable in the low doping regime.Comment: 7 pages, 6 figures, accepted for Phys. Rev.

One-dimensional metallic behavior of the stripe phase in La2−x_{2-x}Srx_xCuO4_4

Using an exact diagonalization method within the dynamical mean-field theory we study stripe phases in the two-dimensional Hubbard model. We find a crossover at doping $\delta\simeq 0.05$ from diagonal stripes to vertical site-centered stripes with populated domain walls, stable in a broad range of doping, $0.05<\delta<0.17$. The calculated chemical potential shift $\propto -\delta^2$ and the doping dependence of the magnetic incommensurability are in quantitative agreement with the experimental results for doped La$_{2-x}$Sr$_x$CuO$_4$. The electronic structure shows one-dimensional metallic behavior along the domain walls, and explains the suppression of spectral weight along the Brillouin zone diagonal.Comment: 4 pages, 4 figure

Metallic mean-field stripes, incommensurability and chemical potential in cuprates

We perform a systematic slave-boson mean-field analysis of the three-band model for cuprates with first-principle parameters. Contrary to widespread believe based on earlier mean-field computations low doping stripes have a linear density close to 1/2 added hole per lattice constant. We find a dimensional crossover from 1D to 2D at doping $\sim 0.1$ followed by a breaking of particle-hole symmetry around doping 1/8 as doping increases. Our results explain in a simple way the behavior of the chemical potential, the magnetic incommensurability, and transport experiments as a function of doping. Bond centered and site-centered stripes become degenerate for small overdoping.Comment: submitted to PR

Time-dependent Gutzwiller approximation for the Hubbard model

We develop a time-dependent Gutzwiller approximation (GA) for the Hubbard model analogous to the time-dependent Hartree-Fock (HF) method. The formalism incorporates ground state correlations of the random phase approximation (RPA) type beyond the GA. Static quantities like ground state energy and double occupancy are in excellent agreement with exact results in one dimension up to moderate coupling and in two dimensions for all couplings. We find a substantial improvement over traditional GA and HF+RPA treatments. Dynamical correlation functions can be easily computed and are also substantially better than HF+RPA ones and obey well behaved sum rules.Comment: 4 pages, 2 figure