C. Gazza | Universidad Nacional de Rosario (UNR) Argentina (original) (raw)
Papers by C. Gazza
The extended t-J model is computationally studied on ladders and planes. At couplings compatible ... more The extended t-J model is computationally studied on ladders and planes. At couplings compatible with photoemission data for undoped cuprates, indications of half-doped metallic stripes separating pi-shifted antiferromagnetic (AF) domains are found, in agreement with usual interpretations of neutron experiments. The basic stripe building block appears in the one-hole state properties, with robust AF across-the-hole correlations, suggesting that the basic seed for stripes is already present in the insulating undoped parent compounds.
Physical Review B, 2000
The hole-doped standard and extended t-J models on ladders with anisotropic Heisenberg interactio... more The hole-doped standard and extended t-J models on ladders with anisotropic Heisenberg interactions are studied computationally in the interval 0.0 ≤ λ ≤ 1.0 (λ = 0, Ising; λ = 1, Heisenberg). It is shown that the approximately half-doped stripes recently discussed at λ = 1 survive in the anisotropic case (λ<1.0), particularly in the "extended" model. Due to the absence of spin fluctuations in the Ising limit and working in the rung basis, a simple picture emerges in which the stripe structure can be mostly constructed from the solution of the t-J model on chains. A comparison of results in the range 0.0 ≤ λ ≤ 1.0 suggests that this picture is valid up to the Heisenberg limit.
Physical Review B, 1999
The spectral function A(q, ω) of doped t − J ladders is presented on clusters with up to 2 × 20 s... more The spectral function A(q, ω) of doped t − J ladders is presented on clusters with up to 2 × 20 sites at zero temperature applying a recently developed technique that uses up to ∼ 6 × 10 6 rungbasis states. Similarities with photoemission results for the 2D cuprates are observed, such as the existence of a gap at (π, 0) near half-filling (caused by hole pair formation) and flat bands in its vicinity. These features should be observable in ARPES experiments on ladders. The main result of the paper is the nontrivial evolution of the spectral function from a narrow band at x = 0, to a quasi-noninteracting band at x ≥ 0.5. It was also observed that the low-energy peaks of a cluster spectra acquire finite line-widths as their energies move away from the chemical potential. PACS numbers: 74.20.-z, 74.20.Mn, 75.25.Dw Copper-oxide ladder compounds are currently under much investigation [1]. Among their interesting properties are a spin-liquid ground state in the undoped limit, and the existence of superconductivity upon hole doping [2,3]. Recently, the first angle-resolved photoemission (ARPES) studies of ladder materials have been reported. Both the doped and undoped ladder Sr 14 Cu 24 O 41 have been analyzed, finding one-dimensional metallic characteristics [4]. Studies of the ladder compound La 1−x Sr x CuO 2.5 found similarities with La 2−x Sr x CuO 4 , including a Fermi edge [5]. Core-level photoemission experiments for (La, Sr, Ca) 14 Cu 24 O 41 documented its chemical shift against hole concentration . Note that the importance of ARPES studies for other materials such as the high-Tc cuprates is by now clearly established . Using this technique the evolution with doping of the Fermi surface has been discussed [8], including the existence of flat bands near momenta (0, π) − (π, 0) [9].
Physical Review Letters, 2002
ABSTRACT A Reply to the Comment by T. K. Lee et al.
Physical Review Letters, 2002
Using computational techniques, it is shown that pairing is a robust property of hole doped antif... more Using computational techniques, it is shown that pairing is a robust property of hole doped antiferromagnetic (AF) insulators. In one dimension (1D) and for two-leg ladder systems, a BCS-like variational wave function with long-bond spin-singlets and a Jastrow factor provides an accurate representation of the ground state of the t-J model, even though strong quantum fluctuations destroy the off-diagonal superconducting (SC) long-range order in this case. However, in two dimensions (2D) it is argued -and numerically confirmed using several techniques, especially quantum Monte Carlo (QMC) -that quantum fluctuations are not strong enough to suppress superconductivity. 74.20.Mn, 71.10.Fd, 71.10.Pm, 71.27.+a
Physical Review Letters, 2006
We investigate a simple model of a frustrated spin-1/2 Heisenberg chain coupled to adiabatic phon... more We investigate a simple model of a frustrated spin-1/2 Heisenberg chain coupled to adiabatic phonons under an external magnetic field. Using field theoretic methods complemented by extensive Density Matrix Renormalisation Group techniques generalized to include self-consistent lattice distortions, we show that magnetization plateaux at non-trivial rational values of the magnetization can be stabilized by the lattice coupling. We suggest that such a scenario could be relevant for some low dimensional frustrated spin-Peierls compounds.
Journal of Physics: Condensed Matter, 2008
We consider the ground state and the elementary excitations of an array of spin-Peierls chains co... more We consider the ground state and the elementary excitations of an array of spin-Peierls chains coupled by elastic and magnetic interactions. It is expected that the effect of the magnetic interchain coupling will be to reduce the dimerization amplitude and that of the elastic coupling will be to confine the spin one-half solitons corresponding to each isolated chain. We show that this is the case when these interactions are not frustrated. On the other hand, in the frustrated case we show that the amplitude of dimerization in the ground state is independent of the strength of the interchain magnetic interaction in a broad range of values of this parameter. We also show that free solitons could be the elementary excitations when only nearest neighbour interactions are considered. The case of an elastic interchain coupling is analyzed on a general energetic consideration. To study the effect of the magnetic interchain interaction the problem is simplified to a two-leg ladder which is solved using density matrix renormalization group (DMRG) calculations. We show that the deconfinement mechanism is effective even with a significantly strong antiferromagnetic interchain coupling. PACS numbers: 75.10.Jm, 75.10.Pq, 75.40.Mg
ABSTRACT A Reply to the Comment by T. K. Lee et al.
We show theoretically the fingerprints of short-range spiral magnetic correlations in the photoem... more We show theoretically the fingerprints of short-range spiral magnetic correlations in the photoemission spectra of the Mott insulating ground states realized in the √ 3 × √ 3 triangular silicon surfaces K/Si(111)-B and SiC(0001). The calculated spectra present low energy features of magnetic origin with a reduced dispersion ∼ 10 − 40 meV compared with the center-of-mass spectra bandwidth ∼ 0.2 − 0.3 eV. Remarkably, we find that the quasiparticle signal survives only around the magnetic Goldstone modes. Our findings would position these silicon surfaces as new candidates to investigate non-conventional quasiparticle excitations.
Physical Review Letters, 2007
We determine the quantum phase diagram of the one-dimensional Hubbard model with bondcharge inter... more We determine the quantum phase diagram of the one-dimensional Hubbard model with bondcharge interaction X in addition to the usual Coulomb repulsion U > 0 at half-filling. For large enough X < t the model shows three phases. For large U the system is in the spin-density wave phase as in the usual Hubbard model. As U decreases, there is first a spin transition to a spontaneously dimerized bond-ordered wave phase and then a charge transition to a novel phase in which the dominant correlations at large distances correspond to an incommensurate singlet superconductor.
The extended t-J model is computationally studied on ladders and planes. At couplings compatible ... more The extended t-J model is computationally studied on ladders and planes. At couplings compatible with photoemission data for undoped cuprates, indications of half-doped metallic stripes separating pi-shifted antiferromagnetic (AF) domains are found, in agreement with usual interpretations of neutron experiments. The basic stripe building block appears in the one-hole state properties, with robust AF across-the-hole correlations, suggesting that the basic seed for stripes is already present in the insulating undoped parent compounds.
Physical Review B, 2000
The hole-doped standard and extended t-J models on ladders with anisotropic Heisenberg interactio... more The hole-doped standard and extended t-J models on ladders with anisotropic Heisenberg interactions are studied computationally in the interval 0.0 ≤ λ ≤ 1.0 (λ = 0, Ising; λ = 1, Heisenberg). It is shown that the approximately half-doped stripes recently discussed at λ = 1 survive in the anisotropic case (λ<1.0), particularly in the "extended" model. Due to the absence of spin fluctuations in the Ising limit and working in the rung basis, a simple picture emerges in which the stripe structure can be mostly constructed from the solution of the t-J model on chains. A comparison of results in the range 0.0 ≤ λ ≤ 1.0 suggests that this picture is valid up to the Heisenberg limit.
Physical Review B, 1999
The spectral function A(q, ω) of doped t − J ladders is presented on clusters with up to 2 × 20 s... more The spectral function A(q, ω) of doped t − J ladders is presented on clusters with up to 2 × 20 sites at zero temperature applying a recently developed technique that uses up to ∼ 6 × 10 6 rungbasis states. Similarities with photoemission results for the 2D cuprates are observed, such as the existence of a gap at (π, 0) near half-filling (caused by hole pair formation) and flat bands in its vicinity. These features should be observable in ARPES experiments on ladders. The main result of the paper is the nontrivial evolution of the spectral function from a narrow band at x = 0, to a quasi-noninteracting band at x ≥ 0.5. It was also observed that the low-energy peaks of a cluster spectra acquire finite line-widths as their energies move away from the chemical potential. PACS numbers: 74.20.-z, 74.20.Mn, 75.25.Dw Copper-oxide ladder compounds are currently under much investigation [1]. Among their interesting properties are a spin-liquid ground state in the undoped limit, and the existence of superconductivity upon hole doping [2,3]. Recently, the first angle-resolved photoemission (ARPES) studies of ladder materials have been reported. Both the doped and undoped ladder Sr 14 Cu 24 O 41 have been analyzed, finding one-dimensional metallic characteristics [4]. Studies of the ladder compound La 1−x Sr x CuO 2.5 found similarities with La 2−x Sr x CuO 4 , including a Fermi edge [5]. Core-level photoemission experiments for (La, Sr, Ca) 14 Cu 24 O 41 documented its chemical shift against hole concentration . Note that the importance of ARPES studies for other materials such as the high-Tc cuprates is by now clearly established . Using this technique the evolution with doping of the Fermi surface has been discussed [8], including the existence of flat bands near momenta (0, π) − (π, 0) [9].
Physical Review Letters, 2002
ABSTRACT A Reply to the Comment by T. K. Lee et al.
Physical Review Letters, 2002
Using computational techniques, it is shown that pairing is a robust property of hole doped antif... more Using computational techniques, it is shown that pairing is a robust property of hole doped antiferromagnetic (AF) insulators. In one dimension (1D) and for two-leg ladder systems, a BCS-like variational wave function with long-bond spin-singlets and a Jastrow factor provides an accurate representation of the ground state of the t-J model, even though strong quantum fluctuations destroy the off-diagonal superconducting (SC) long-range order in this case. However, in two dimensions (2D) it is argued -and numerically confirmed using several techniques, especially quantum Monte Carlo (QMC) -that quantum fluctuations are not strong enough to suppress superconductivity. 74.20.Mn, 71.10.Fd, 71.10.Pm, 71.27.+a
Physical Review Letters, 2006
We investigate a simple model of a frustrated spin-1/2 Heisenberg chain coupled to adiabatic phon... more We investigate a simple model of a frustrated spin-1/2 Heisenberg chain coupled to adiabatic phonons under an external magnetic field. Using field theoretic methods complemented by extensive Density Matrix Renormalisation Group techniques generalized to include self-consistent lattice distortions, we show that magnetization plateaux at non-trivial rational values of the magnetization can be stabilized by the lattice coupling. We suggest that such a scenario could be relevant for some low dimensional frustrated spin-Peierls compounds.
Journal of Physics: Condensed Matter, 2008
We consider the ground state and the elementary excitations of an array of spin-Peierls chains co... more We consider the ground state and the elementary excitations of an array of spin-Peierls chains coupled by elastic and magnetic interactions. It is expected that the effect of the magnetic interchain coupling will be to reduce the dimerization amplitude and that of the elastic coupling will be to confine the spin one-half solitons corresponding to each isolated chain. We show that this is the case when these interactions are not frustrated. On the other hand, in the frustrated case we show that the amplitude of dimerization in the ground state is independent of the strength of the interchain magnetic interaction in a broad range of values of this parameter. We also show that free solitons could be the elementary excitations when only nearest neighbour interactions are considered. The case of an elastic interchain coupling is analyzed on a general energetic consideration. To study the effect of the magnetic interchain interaction the problem is simplified to a two-leg ladder which is solved using density matrix renormalization group (DMRG) calculations. We show that the deconfinement mechanism is effective even with a significantly strong antiferromagnetic interchain coupling. PACS numbers: 75.10.Jm, 75.10.Pq, 75.40.Mg
ABSTRACT A Reply to the Comment by T. K. Lee et al.
We show theoretically the fingerprints of short-range spiral magnetic correlations in the photoem... more We show theoretically the fingerprints of short-range spiral magnetic correlations in the photoemission spectra of the Mott insulating ground states realized in the √ 3 × √ 3 triangular silicon surfaces K/Si(111)-B and SiC(0001). The calculated spectra present low energy features of magnetic origin with a reduced dispersion ∼ 10 − 40 meV compared with the center-of-mass spectra bandwidth ∼ 0.2 − 0.3 eV. Remarkably, we find that the quasiparticle signal survives only around the magnetic Goldstone modes. Our findings would position these silicon surfaces as new candidates to investigate non-conventional quasiparticle excitations.
Physical Review Letters, 2007
We determine the quantum phase diagram of the one-dimensional Hubbard model with bondcharge inter... more We determine the quantum phase diagram of the one-dimensional Hubbard model with bondcharge interaction X in addition to the usual Coulomb repulsion U > 0 at half-filling. For large enough X < t the model shows three phases. For large U the system is in the spin-density wave phase as in the usual Hubbard model. As U decreases, there is first a spin transition to a spontaneously dimerized bond-ordered wave phase and then a charge transition to a novel phase in which the dominant correlations at large distances correspond to an incommensurate singlet superconductor.