I. J. Hamad

1/T1 nuclear relaxation time of κ-(BEDT–TTF)2Cu[N(CN)2]Cl : effects of magnetic frustration

We study the role played by the magnetic frustration in the antiferromagnetic phase of the organic salt κ-(BEDT–TTF)2Cu[N(CN)2]Cl. Using the spatially anisotropic triangular Heisenberg model we analyse previous and newly performed NMR experiments. We compute the 1/T1 relaxation time by means of the modified spin wave theory. The strong suppression of the nuclear relaxation time observed experimentally under varying pressure and magnetic field is qualitatively well reproduced by the model. Our results suggest the existence of a close relation between the effects of pressure and magnetic frustration.

Effects of semiclassical spiral fluctuations on hole dynamics

We investigate the dynamics of a single hole coupled to the spiral fluctuations related to the magnetic ground states of the antiferromagnetic J_1-J_2-J_3 Heisenberg model on a square lattice. Using exact diagonalization on finite size clusters and the self consistent Born approximation in the thermodynamic limit we find, as a general feature, a strong reduction of the quasiparticle weight along the spiral phases of the magnetic phase diagram. For an important region of the Brillouin Zone the hole spectral functions are completely incoherent, whereas at low energies the spectral weight is redistributed on several irregular peaks. We find a characteristic value of the spiral pitch, Q=(0.7,0.7)\pi, for which the available phase space for hole scattering is maximum. We argue that this behavior is due to the non trivial interference of the magnon assisted and the free hopping mechanism for hole motion, characteristic of a hole coupled to semiclassical spiral fluctuations.

Spin polaron in the J 1 − J 2 Heisenberg model

We have studied the validity of the spin polaron picture in the frustrated J1-J2 Heisenberg model. For this purpose, we have computed the hole spectral functions for the Neel, collinear, and disordered phases of this model, by means of the self-consistent Born approximation and Lanczos exact diagonalization on finite-size clusters. We have found that the spin polaron quasiparticle excitation is always well defined for the magnetically ordered Neel and collinear phases, even in the vicinity of the magnetic quantum critical points, where the local magnetization vanishes. As a general feature, the effect of frustration is to increase the amplitude of the multimagnon states that build up the spin polaron wave function, leading to the reduction of the quasiparticle coherence. Based on Lanczos results, we discuss the validity of the spin polaron picture in the disordered phase.

Spectroscopic fingerprints of the frustrated magnetic order in Li2VOSiO4: A t–J model study

We have analyzed theoretically the photoemission spectra of the insulating compound Li2VOSiO4Li2VOSiO4. Recently, this compound has been proposed as the first experimental realization of the frustrated J1–J2J1–J2 Heisenberg model. Although it is well known that Li2VOSiO4Li2VOSiO4 is magnetically ordered in a collinear arrangement below TN=2.8K, there is some controversy about the coexistence of two collinear phases above TNTN. Using a generalized t–Jt–J model we have obtained a complex spectral structure that can be traced back to the underlying collinear magnetic structures. We discuss the possibility to use ARPES experiments as a way to discern among the different scenarios proposed in the literature.

Spin polaron in the J1-J2 Heisenberg model

We have studied the validity of the spin polaron picture in the frustrated J1-J2 Heisenberg model. For this purpose, we have computed the hole spectral functions for the Neel, collinear, and disordered phases of this model, by means of the self-consistent Born approximation and Lanczos exact diagonalization on finite-size clusters. We have found that the spin polaron quasiparticle excitation is always well defined for the magnetically ordered Neel and collinear phases, even in the vicinity of the magnetic quantum critical points, where the local magnetization vanishes. As a general feature, the effect of frustration is to increase the amplitude of the multimagnon states that build up the spin polaron wave function, leading to the reduction of the quasiparticle coherence. Based on Lanczos results, we discuss the validity of the spin polaron picture in the disordered phase.

Spin polaron in theJ1−J2Heisenberg model

We have studied the validity of the spin polaron picture in the frustrated J1-J2 Heisenberg model. For this purpose, we have computed the hole spectral functions for the Neel, collinear, and disordered phases of this model, by means of the self-consistent Born approximation and Lanczos exact diagonalization on finite-size clusters. We have found that the spin polaron quasiparticle excitation is always well defined for the magnetically ordered Neel and collinear phases, even in the vicinity of the magnetic quantum critical points, where the local magnetization vanishes. As a general feature, the effect of frustration is to increase the amplitude of the multimagnon states that build up the spin polaron wave function, leading to the reduction of the quasiparticle coherence. Based on Lanczos results, we discuss the validity of the spin polaron picture in the disordered phase.

Spectroscopic fingerprints of the frustrated magnetic order in Li2VOSiO4Li2VOSiO4: A t–Jt–J model study

We have analyzed theoretically the photoemission spectra of the insulating compound Li2VOSiO4Li2VOSiO4. Recently, this compound has been proposed as the first experimental realization of the frustrated J1–J2J1–J2 Heisenberg model. Although it is well known that Li2VOSiO4Li2VOSiO4 is magnetically ordered in a collinear arrangement below TN=2.8K, there is some controversy about the coexistence of two collinear phases above TNTN. Using a generalized t–Jt–J model we have obtained a complex spectral structure that can be traced back to the underlying collinear magnetic structures. We discuss the possibility to use ARPES experiments as a way to discern among the different scenarios proposed in the literature.

Spectroscopic fingerprints of the frustrated magnetic order in : A model study

We have analyzed theoretically the photoemission spectra of the insulating compound Li2VOSiO4Li2VOSiO4. Recently, this compound has been proposed as the first experimental realization of the frustrated J1–J2J1–J2 Heisenberg model. Although it is well known that Li2VOSiO4Li2VOSiO4 is magnetically ordered in a collinear arrangement below TN=2.8K, there is some controversy about the coexistence of two collinear phases above TNTN. Using a generalized t–Jt–J model we have obtained a complex spectral structure that can be traced back to the underlying collinear magnetic structures. We discuss the possibility to use ARPES experiments as a way to discern among the different scenarios proposed in the literature.

Hole dynamics in canted antiferromagnets : Coexistence of many-body and free-like excitations

We have analyzed the dynamics of a single hole doped in a canted antiferromagnet using the

Publisher's Note: Spin polaron in theJ1−J2Heisenberg model [Phys. Rev. B77, 014410 (2008)]

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