In considering next-nearest neighbor （NNN） coupling, we numerically investigate the magnetoelastic instability in ring-shaped mesoscopic antiferromagnetic Heisenberg spin 1/2 systems with spin-phonon interaction. Th...In considering next-nearest neighbor （NNN） coupling, we numerically investigate the magnetoelastic instability in ring-shaped mesoscopic antiferromagnetic Heisenberg spin 1/2 systems with spin-phonon interaction. The results indicate that, for antiferromagnetic NNN coupling J2, there may be a critical value J2^c, at which the ground state is dimerized for arbitrary lattice spring constant and beyond and below which the magnetoelastic instability behavior is different from each other. The values of J2^c are irrelevant to the system size. For ferromagnetic NNN coupling, only continuous transition is present from dimerized phase to uniform phase as lattice spring constant is increased.展开更多
A two-leg S=1/2 spin ladder with ferromagnetic rung coupling is investigated to reveal the phase transition between the Haldane and columnar dimer phase.The elastic lattice with the elastic force K is introduced into ...A two-leg S=1/2 spin ladder with ferromagnetic rung coupling is investigated to reveal the phase transition between the Haldane and columnar dimer phase.The elastic lattice with the elastic force K is introduced into the system,which induces unstable spin chains towards the spontaneous dimerization.When the rung coupling is strong enough,the dimerization along the legs is suppressed and the spin ladder undergoes a phase transition.The dimerization amplitude is calculated self-consistently by the density-matrix renormalization group method.To determine the phase transition boundary,the spin gap,the columnar dimer order parameter and the block-block entanglement entropy are calculated.Our results show that the phase boundary between the columnar dimer phase and Haldane phase follows the power law J_(t)-K^(-α).展开更多
A spin-polarized current direction controller scheme is proposed based on a nonuniform Rashba quantum wire. It is shown that |P_(z)^(LR)|=|P_(z)^(RL)|, whereas their signs are opposite, and the effect of this phenomen...A spin-polarized current direction controller scheme is proposed based on a nonuniform Rashba quantum wire. It is shown that |P_(z)^(LR)|=|P_(z)^(RL)|, whereas their signs are opposite, and the effect of this phenomenon is due to the two broken symmetries and the unbroken C_(2)-rotation symmetry of the investigated system. In addition, the spin-polarized current is nonzero even with a strong disorder strength, which demonstrates that this structure may be utilized for potential applications.展开更多
Within an extended Su–Schrieffer–Heeger model including impurity interactions,the dynamical process of exciton dissociation in the presence of an external electric field is investigated by using a non-adiabatic evol...Within an extended Su–Schrieffer–Heeger model including impurity interactions,the dynamical process of exciton dissociation in the presence of an external electric field is investigated by using a non-adiabatic evolution method.Under the action of impurities,the stability as well as the effective mass of the exciton is reduced.Our results show that the field required to dissociate the excitons depends sensitively on the strength of the impurity potential.As the impurity potential strength increases,the dissociation field decreases effectively.The theoretical results are expected to provide useful predictions concerning which polymers with properly impurity-assisted interactions are likely to be more suitable for use in organic solar cells.展开更多
文摘In considering next-nearest neighbor （NNN） coupling, we numerically investigate the magnetoelastic instability in ring-shaped mesoscopic antiferromagnetic Heisenberg spin 1/2 systems with spin-phonon interaction. The results indicate that, for antiferromagnetic NNN coupling J2, there may be a critical value J2^c, at which the ground state is dimerized for arbitrary lattice spring constant and beyond and below which the magnetoelastic instability behavior is different from each other. The values of J2^c are irrelevant to the system size. For ferromagnetic NNN coupling, only continuous transition is present from dimerized phase to uniform phase as lattice spring constant is increased.
基金Supported by the National Natural Science Foundation of China under Grant No 10904112the Qianjiang Talent Project under Grant No 2012R10074。
文摘A two-leg S=1/2 spin ladder with ferromagnetic rung coupling is investigated to reveal the phase transition between the Haldane and columnar dimer phase.The elastic lattice with the elastic force K is introduced into the system,which induces unstable spin chains towards the spontaneous dimerization.When the rung coupling is strong enough,the dimerization along the legs is suppressed and the spin ladder undergoes a phase transition.The dimerization amplitude is calculated self-consistently by the density-matrix renormalization group method.To determine the phase transition boundary,the spin gap,the columnar dimer order parameter and the block-block entanglement entropy are calculated.Our results show that the phase boundary between the columnar dimer phase and Haldane phase follows the power law J_(t)-K^(-α).
基金the National Natural Science Foundation of China under Grant No 11247207the Research Foundation of Jiangxi Education Department under Grant Nos GJJ12355 and GJJ13383the Natural Science Foundation of Jiangxi Province under Grant No 20122BAB212004.
文摘A spin-polarized current direction controller scheme is proposed based on a nonuniform Rashba quantum wire. It is shown that |P_(z)^(LR)|=|P_(z)^(RL)|, whereas their signs are opposite, and the effect of this phenomenon is due to the two broken symmetries and the unbroken C_(2)-rotation symmetry of the investigated system. In addition, the spin-polarized current is nonzero even with a strong disorder strength, which demonstrates that this structure may be utilized for potential applications.
基金by the National Natural Science Foundation of China.
文摘Within an extended Su–Schrieffer–Heeger model including impurity interactions,the dynamical process of exciton dissociation in the presence of an external electric field is investigated by using a non-adiabatic evolution method.Under the action of impurities,the stability as well as the effective mass of the exciton is reduced.Our results show that the field required to dissociate the excitons depends sensitively on the strength of the impurity potential.As the impurity potential strength increases,the dissociation field decreases effectively.The theoretical results are expected to provide useful predictions concerning which polymers with properly impurity-assisted interactions are likely to be more suitable for use in organic solar cells.
