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Enrico Arrigoni

Publications and source records attributed to Enrico Arrigoni.

66 records · Page 4Linked to original sources
arXiv2010

Spectral properties of strongly correlated bosons in two-dimensional optical lattices

Spectral properties of the two-dimensional Bose-Hubbard model, which emulates ultracold gases of atoms confined in optical lattices, are investigated by means of the variational cluster approach. The phase boundary of the quantum phase transition from Mott phase to superfluid phase is calculated and compared to recent work. Moreover the single-particle spectral functions in both the first and the second Mott lobe are presented and the corresponding densities of states and momentum distributions are evaluated. A qualitatively similar intensity distribution of the spectral weight can be observed for spectral functions in the first and the second Mott lobe.

cond-mat.quant-gas↗
arXiv2005

Correlated band structure and the ground-state phase diagram in high-Tc cuprates

We review results obtained with a recently proposed variational cluster approach (VCA) for the competition between d-wave superconductivity (dSC) and antiferromagnetism (AF) in the high-Tc cuprates. Comparing the single-particle spectra of a two-dimensional Hubbard model with quantum Monte-Carlo (QMC) and experimental data, we verify that the VCA correctly treats the low-energy excitations. The cluster calculations reproduce the overall ground-state phase diagram of the high-temperature superconductors both for electron- and hole-doping. In particular, they include salient features such as the enhanced robustness of the AF state in case of electron doping. For electron- but also for hole-doping, we clearly identify a tendency to phase separation into a mixed AF-dSC phase at low and a pure dSC-phase at high doping.

cond-mat.supr-con↗
arXiv2001

Evolution of the stripe phase as a function of doping from a theoretical analysis of angle-resolved photoemission data

By comparing single-particle spectral functions of t-J and Hubbard models with recent angle-resolved photoemission (ARPES) results for LSCO and Nd-LSCO, we can decide where holes go as a function of doping, and more specifically, which type of stripe (bond-, site-centered) is present in these materials at a given doping. For dopings greater than about 12% our calculation shows furthermore that the holes prefer to proliferate out of the metallic stripes into the neighboring antiferromagnetic domains. The spectra were calculated by a cluster perturbation technique, for which we present an alternative formulation. Implications for the theory for high-Tc superconductivity are discussed.

cond-mat.str-el↗
arXiv2000

t-U-W Model of a d_{x^2-y^2} Superconductor in the Proximity of an AF Mott Insulator: Diagrammatic Studies vs. QMC Simulations

We examine the competition and relationship between an antiferromagnetic (AF) Mott insulating state and a d_{x^2-y^2} superconducting (SC) state in two dimensions using semi-analytical, i. e. diagrammatic calculations of the t-U-W model. The AF Mott insulator is described by the ground state of the half-filled Hubbard model on a square lattice with on-site Coulomb repulsion U and nearest neighbor single-particle hopping t. To this model, an extra term W is added, which depends upon the square of the single-particle nearest-neighbor hopping. Staying at half-band filling and a constant value of U, it was previously shown with Quantum-Monte-Carlo (QMC) simulations that one can generate a quantum transition as a function of the coupling strength, W, between an AF Mott insulating state and a d_{x^2-y^2} SC state. Here we complement these earlier QMC simulations with physically more transparent diagrammatic calculations. We start with a standard Hartree-Fock (HF) calculation to capture the "high-energy" physics of the t-U-W model. Then, we derive and solve the Bethe-Salpeter equation, i. e. we account for fluctuation effects within the time-dependent HF or generalized RPA scheme. Spin- and charge-susceptibility as well as the effective interaction vertex are calculated and systematically compared with QMC data. Finally, the corresponding BCS gap equation obtained for this effective interaction is solved.

cond-mat.supr-con↗
arXiv2000

Stripes in Doped Antiferromagnets: Single-Particle Spectral Weight

Recent photoemission (ARPES) experiments on cuprate superconductors provide important guidelines for a theory of electronic excitations in the stripe phase. Using a cluster perturbation theory, where short-distance effects are accounted for by exact cluster diagonalization and long-distance effects by perturbation (in the hopping), we calculate the single-particle Green's function for a striped t-J model. The data obtained quantitatively reproduce salient (ARPES-) features and may serve to rule out "bond-centered" in favor of "site-centered" stripes.

cond-mat.str-el↗
arXiv2000

Interrelation of Superconducting and Antiferromagnetic Gaps in High-Tc Compounds: a Test Case for the SO(5) Theory

Recent angle resolved photoemission data, which found evidence for a d-wave-like modulation of the antiferromagnetic gap, suggest an intimate interrelation between the antiferromagnetic insulator and the superconductor with its d-wave gap. It is shown here that a projected SO(5) theory, which explicitly takes the Mott-Hubbard gap into account, correctly describes the observed gap characteristics. Specifically, it accounts for the order of magnitude difference between the antiferromagnetic gap modulation and the superconducting gap and is also consistent with the gap dispersion.

cond-mat.str-el↗
arXiv1999

Projected SO(5) Models

We construct a class of projected SO(5) models where the Gutzwiller constraint of no-double-occupancy is implemented exactly. We introduce the concept of projected SO(5) symmetry where all static correlation functions are exactly SO(5) symmetric and discuss the signature of the projected SO(5) symmetry in dynamical correlation functions. We show that this class of projected SO(5) models can give a realistic description of the global phase diagram of the high T_c superconductors and account for many of their physical properties.

cond-mat↗
arXiv1999

Interrelation of Superconducting and Antiferromagnetic Gaps in High-Tc Compounds: a Test Case for a Microscopic Theory

Recent angle resolved photoemission (ARPES) data, which found evidence for a d-wave-like modulation of the antiferromagnetic gap, suggest an intimate interrelation between the antiferromagnetic insulator and the superconductor with its d-wave gap. This poses a new challenge to microscopic descriptions, which should account for this correlation between, at first sight, very different states of matter. Here, we propose a microscopic mechanism which provides a definite correlation between these two different gap structures: it is shown that a projected SO(5) theory, which aims at unifying antiferromagnetism and d-wave superconductivity via a common symmetry principle while explicitly taking the Mott-Hubbard gap into account, correctly describes the observed gap characteristics. Specifically, it accounts for both the dispersion and the order of magnitude difference between the antiferromagnetic gap modulation and the superconducting gap.

cond-mat.str-el↗
arXiv1999

Crossover from Luttinger- to Fermi-liquid behavior in strongly anisotropic systems in large dimensions

We consider the low-energy region of an array of Luttinger liquids coupled by a weak interchain hopping. The leading logarithmic divergences can be re-summed to all orders within a self-consistent perturbative expansion in the hopping, in the large-dimension limit. The anomalous exponent scales to zero below the one-particle crossover temperature. As a consequence, coherent quasiparticles with finite weight appear along the whole Fermi surface. Extending the expansion self-consistently to all orders turns out to be crucial in order to restore the correct Fermi-liquid behavior.

cond-mat.str-el↗
arXiv1997

Interchain coherence of coupled Luttinger liquids at all orders in perturbation theory

We analyze the problem of Luttinger liquids coupled via a single-particle hopping $\tp$ and introduce a systematic diagrammatic expansion in powers of $\tp$. An analysis of the scaling of the diagrams at each order allows us to determine the power-law behavior versus $\tp$ of the interchain hopping and of the Fermi surface warp. In particular, for strong interactions, we find that the exponents are dominated by higher-order diagrams producing an enhanced coherence and a failure of linear-response theory. Our results are valid at any finite order in $\tp$ for the self-energy.

cond-mat.str-el↗
arXiv1996

Renormalization-Group Approach to a Three-Legs Fermionic Ladder

We study the spin and charge phase diagram of a three-legs ladder (at zero temperature) as a function of fermion density and of transverse single-particle hopping by means of a Renormalization-Group analysis rigorously controlled in the weak-coupling limit. Periodic boundary conditions in the direction transverse to the ladder produce frustrated magnetic excitations yielding a spin-gapped phase in a large region about and at half filling. Spin correlations are instead enhanced when open transverse boundary conditions are considered, yielding an ungapped phase in a wide region about half filling (as observed in the Sr$_{n-1}$Cu$_{n+1}$O$_{2n}$ stripes compounds) and at half filling down to a critical value of the transverse hopping $t_{\perp}$. At that critical value, the system undergoes a Mott transition at half filling by decreasing $t_{\perp}$.

cond-mat↗