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We study the low‐temperature properties of a mixed $(S,s) = (3/2,1/2)$ alternating quantum spin chain with antiferromagnetic–ferromagnetic bond alternation and single‐ion anisotropy using spin‐wave theory, density‐matrix renormalization... more
We study the low‐temperature properties of a mixed $(S,s) = (3/2,1/2)$ alternating quantum spin chain with antiferromagnetic–ferromagnetic bond alternation and single‐ion anisotropy using spin‐wave theory, density‐matrix renormalization group calculations and exact diagonalization of finite clusters. An instance in this system is the recently synthesized bimetallic chain $^{1} _{\infty } $ [LCuIICoII(NCS)2], which shows a novel magnetic behavior, namely, the ${\chi} _{M} T$ versus $T$ curve decreases rapidly at low temperatures after displaying a pseudo‐plateau around a certain intermediate temperature. There are two different mechanisms which could explain this unconventional feature: the zero‐field splitting of the ground state and/or the ferromagnetic nature of the interdimer interactions. We clarify the role of these two kinds of mechanisms in the observed properties of the system by deviating from the otherwise‐expected ferrimagnetic ground state and considering a slight deviat...
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The binding energy of heavy hole excitons in a spherical GaAs–Ga1–x Alx As quantum dot under isotropic hydrostatic pressure was calculated using the Hylleraas coordinate system and a variational approach within the approximation of the... more
The binding energy of heavy hole excitons in a spherical GaAs–Ga1–x Alx As quantum dot under isotropic hydrostatic pressure was calculated using the Hylleraas coordinate system and a variational approach within the approximation of the effective mass. The influences of hydrostatic pressure on the effective masses of the electron and the heavy hole, the dielectric constant and the conduction‐ and valence‐band offsets between the well and the barriers are taken into account in the calculation. The binding energy is computed as a function of hydrostatic pressure, the dot sizes and the Al(x) concentration. The results show that the binding energy derived from exciton increases with the pressure, especially for small quantum dots. Also, we have found that the binding energy increases with the pressure and the concentration for a fixed quantum dot radius, which can be useful for technological applications. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
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Submitted for the MAR16 Meeting of The American Physical Society Phase diagrams of spinor bosons in two-leg ladders.1 JERESON SILVA VALENCIA, ROBERTO FRANCO, Universidad Nacional de Colombia, MARCOS SERGIO FIGUEIRA, Universidade Federal... more
Submitted for the MAR16 Meeting of The American Physical Society Phase diagrams of spinor bosons in two-leg ladders.1 JERESON SILVA VALENCIA, ROBERTO FRANCO, Universidad Nacional de Colombia, MARCOS SERGIO FIGUEIRA, Universidade Federal Fluminense — In the last, years different experimental groups have reported the realization of atomic ladders in the presence of a homogeneous flux [Nat. Phys. 10, 588 (2014)]. These experiments have motivated theoretical calculations on 2-leg ladders with spinless bosons under magnetic fields [PRB 91, 140406(R) (2015)]. In this paper, we consider spinor boson atoms with spin S=1, such as Rb and Na. Gases of these atoms can be described by the spinor Bose-Hubbard Hamiltonian which has three terms: the kinetic energy, local density-density interaction and local spin-dependent term. Using DMRG, we study S=1 bosons on 2-leg ladders, taking into account bothantiferromagnetic and ferromagneticspin interaction. When both legs are ferromagnetic or antiferro...
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Abstract The magnetization curve of the spin superlattices composed of repeat pattern of two spin- 1 2 XXZ chains with different anisotropy parameters was calculated using density matrix renormalization group. We observe a nontrivial... more
Abstract The magnetization curve of the spin superlattices composed of repeat pattern of two spin- 1 2 XXZ chains with different anisotropy parameters was calculated using density matrix renormalization group. We observe a nontrivial plateau with magnetization value given by the relative sizes of the subchains.
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We study the von Neumann block entropy in the Kondo necklace model for different anisotropies $\ensuremath{\eta}$ in the $\mathit{XY}$ interaction between conduction spins using the density matrix renormalization group method. It was... more
We study the von Neumann block entropy in the Kondo necklace model for different anisotropies $\ensuremath{\eta}$ in the $\mathit{XY}$ interaction between conduction spins using the density matrix renormalization group method. It was found that the block entropy presents a maximum for each $\ensuremath{\eta}$ considered, and, comparing it with the results of the quantum criticality of the model based on the behavior of the energy gap, we observe that the maximum block entropy occurs at the quantum critical point between an antiferromagnetic and a Kondo singlet state, so this measure of entanglement is useful for giving information about where a quantum phase transition occurs in this model. We observe that the block entropy also presents a maximum at the quantum critical points that are obtained when an anisotropy $\ensuremath{\Delta}$ is included in the Kondo exchange between localized and conduction spins; when $\ensuremath{\Delta}$ diminishes for a fixed value of $\ensuremath{\eta}$, the critical point increases, favoring the antiferromagnetic phase.
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We study numerically a one-dimensional mixture of spin-1 2 fermions and scalar bosons in the hard-core limit. Considering repulsive fermion-fermion and boson-fermion interactions, we find superfluid and insulator states, and determine the... more
We study numerically a one-dimensional mixture of spin-1 2 fermions and scalar bosons in the hard-core limit. Considering repulsive fermion-fermion and boson-fermion interactions, we find superfluid and insulator states, and determine the boundaries between them calculating several phase diagrams. We determine that, given a fermionic density ρ F , the insulator states are located at the bosonic densities ρ B = 1 − ρ F and 1 − 1 2 ρ F , and emerge even in the absence of fermion-fermion coupling. In addition, the boson-fermion repulsion drives quantum phase transitions inside the insulator lobes with ρ B = 1/2. Our predictions could be observed in current cold-atom experimental platforms.