Rashba spin-orbit interaction and shot noise for spin-polarized and entangled electrons

We study shot noise for spin-polarized currents and entangled electron pairs in a four-probe (beam-splitter) geometry with a local Rashba spin-orbit (s-o) interaction in the incoming leads. Within the scattering formalism we find that shot noise exhibits Rashba-induced oscillations with continuous bunching and antibunching. We show that entangled states and triplet states can be identified via their Rashba phase in noise measurements. For two-channel leads, we find an additional spin rotation due to s-o induced interband coupling which enhances spin control. We show that the s-o interaction deter-mines the Fano factor, which provides a direct way to measure the Rashba coupling constant via noise.     

Microscopic Study of Band Structures in98-102Sr and 100-104Zr Isotopes

The properties of the high spin states of the neutron-rich ^98-102Sr and ^100-104Zr isotopes have been studied using the projected shell model. In particular, the upbending phenomenon is investigated for these isotopes along the yrast line. The results show that the occurrence of upbending phenomenon is
attributed to the band crossing between ground state band and 2-qp neutron band having configuration 2νh_{11 / 2}[-3/2, 5/2], K=1. Furthermore, the neutron two-quasi-particle structure of side bands in ⁹⁸Sr and ¹⁰²Zr is discussed in this paper.     

微波调制的里德堡原子集体量子跳跃

对于一个三能级原子体系,原子的两个基态能级通过微波耦合起来,其中一个基态能级可被激发到里德堡态,从而可观察量子跳跃现象.本文采用量子轨线方法研究了微波调制的里德堡原子集体量子跳跃.研究结果表明,微波耦合基态能级可以提高光子关联,增强光子聚束效应,即使较少的原子中也可以观察到系统在高里德堡占据数态和低里德堡占据数态之间的切换.这一结果为将来进一步研究里德堡自旋晶格中的多体动力学提供了新思路.     

Structure analysis of 159Sm and properties of odd-mass neutron-rich nuclei in mass-160 region

Recent fission experiment data provide interesting structure information for neutron-rich nuclei in the mass A ∼ 160 region. We apply the projected shell model to study the strongly-deformed, neutron-rich Sm isotopes. We perform calculations for rotational bands up to spin I = 20 (29/2) for even-even (odd-neutron) Sm isotopes, and analyze the band structure of low-lying states with quasiparticle excitations. Emphasis is given to rotational bands based on one-quasiparticle (1-qp) configurations in the odd-mass ¹⁵⁹Sm. The ¹⁵⁹Sm result is discussed together with those of the even-even isotopes ^158,160Sm. New bands in ¹⁵⁹Sm based on neutron 1-qp 1/2⁻ and 5/2⁺ configurations are predicted. Electromagnetic transition probabilities are discussed.

     

自旋-轨道耦合对磁性绝缘体磁光Kerr效应的影响

采用单原子能级跃迁模型,导出在同时考虑自旋交换劈裂和自旋轨道耦合时磁光Kerr旋转的微观表达式,并就四能级跃迁情况,研究了磁光效应随原子基态及激发态能级自旋轨道耦合常数的变化规律.结果表明:磁光Kerr旋转角与自旋轨道耦合劈裂能量不成正比;单原子能级自旋轨道耦合常数为正或中间激发态自旋轨道耦合常数为负时,有利于提高磁光Kerr旋转. 关键词： 磁光Kerr效应 自旋轨道耦合 线性响应核 劈裂     

Competing pairing symmetries in a generalized two-orbital model for the pnictide superconductors

We introduce and study an extended "t-U-J" two-orbital model for the pnictides that includes Heisenberg terms deduced from the strong coupling expansion. Including these J terms explicitly allows us to enhance the strength of the (π,0)-(0,π) spin order which favors the presence of tightly bound pairing states even in the small clusters that are here exactly diagonalized. The A(1g) and B(2g) pairing symmetries are found to compete in the realistic spin-ordered and metallic regime. The dynamical pairing susceptibility additionally unveils low-lying B(1g) states, suggesting that small changes in parameters may render any of the three channels stable.     

Conductance oscillations of a spin-orbit stripe with polarized contacts

We investigate the linear conductance of a stripe of spin-orbit interaction in a 2D electron gas; that is, a 2D region of length l\ell along the transport direction and infinite in the transverse one in which a spin-orbit interaction of Rashba type is present. Polarization in the contacts is described by means of Zeeman fields. Our model predicts two types of conductance oscillations: Ramsauer oscillations in the minority spin transmission, when both spins can propagate, and Fano oscillations when only one spin propagates. The latter are due to the spin-orbit coupling with quasibound states of the non propagating spin. In the case of polarized contacts in antiparallel configuration Fano-like oscillations of the conductance are still made possible by the spin orbit coupling, even though no spin component is bound by the contacts. To describe these behaviors we propose a simplified model based on an ansatz wave function. In general, we find that the contribution for vanishing transverse momentum dominates and defines the conductance oscillations. Regarding the oscillations with Rashba coupling intensity, our model confirms the spin transistor behavior, but only for high degrees of polarization. Including a position dependent effective mass yields additional oscillations due to the mass jumps at the interfaces.     

Ni^2＋：CsMgCl3的光学吸收谱和EPR的研究

应用三角晶场中d^2(d^8)电子组态包括静电相互作用和自旋－轨道耦合作用的强场能量矩阵,采用完全对角化方法,精确地计算了具有D3d对称的Ni^2 :CsMgCl3的光学吸收谱和EPR谱,理论结果与实验值符合得很好。     

Reggeon quantum mechanics: Effect of four-reggeon couplings

We study reggeon quantum mechanics when four-reggeon couplings are present as well as the conventional three-reggeon coupling. We show that as the reggeon intercept is increased an infinite number of states pass through energy zero. We give the values of the intercepts at which states pass through zero, construct the states explicitly, and tell how fast their energy changes with intercept. We show that these higher states do not interfere with the construction of spin models. However, no spin model is possible if the one-reggeon ? three-reggeon coupling is non-zero.     

Quantum spin Hall and quantum valley Hall effects in trilayer graphene and their topological structures

The present study pertains to the trilayer graphene in the presence of spin orbit coupling to probe the quantum spin/valley Hall effect. The spin Chern-number C_s for energy-bands of trilayer graphene having the essence of intrinsic spin–orbit coupling is analytically calculated. We find that for each valley and spin, C_s is three times larger in trilayer graphene as compared to single layer graphene. Since the spin Chern-number corresponds to the number of edge states,consequently the trilayer graphene has edge states, three times more in comparison to single layer graphene. We also study the trilayer graphene in the presence of both electric-field and intrinsic spin–orbit coupling and investigate that the trilayer graphene goes through a phase transition from a quantum spin Hall state to a quantum valley Hall state when the strength of the electric field exceeds the intrinsic spin coupling strength. The robustness of the associated topological bulk-state of the trilayer graphene is evaluated by adding various perturbations such as Rashba spin–orbit(RSO) interaction αR, and exchange-magnetization M. In addition, we consider a theoretical model, where only one of the outer layers in trilayer graphene has the essence of intrinsic spin–orbit coupling, while the other two layers have zero intrinsic spin–orbit coupling.Although the first Chern number is non-zero for individual valleys of trilayer graphene in this model, however, we find that the system cannot be regarded as a topological insulator because the system as a whole is not gaped.     

Local moment formation in the superconducting state of a doped Mott insulator

A microscopic theory is presented for the local moment formation near a nonmagnetic impurity or a copper defect in high-Tc superconductors. We use a renormalized mean-field theory of the t-J model for a doped Mott insulator and study the fully self-consistent, spatially unrestricted solutions of the d-wave superconducting (SC) state in both the spin S=0 and S=1/2 sectors. We find a transition from the singlet d-wave SC state to a spin doublet SC state when the renormalized exchange coupling exceeds a doping dependent critical value. The induced S=1/2 moment is staggered and localized around the impurity. It arises from the binding of an S=1/2 nodal quasiparticle to the impurity. The local density of states is calculated and connections to NMR and STM experiments are discussed.     

Spin wave impurity states in linear chain ferromagnets and antiferromagnets

A simple linear chain model is used to find the perturbed states in Heisenberg ferromagnets and antiferromagnets with a magnetic impurity. The defect is characterized by a different nearest neighbor exchange coupling, spin, anisotropy field and gyromagnetic ratio from the corresponding parameters for the host lattice. A semiclassical calculation demonstrates that for some values of the defect parameters, resonant states in the spin wave band can arise near the bottom of the band, while for other values, localized states will occur. The various physical conditions for the occurrence of those states are given. When an applied magnetic field is included in the model calculation, a gap mode instability can occur for some values of the gyromagnetic ratio of the impurity spin. For some combinations of defect parameters, a local mode can be transformed into a resonant mode and vice versa by the magnetic field. The impurity-induced absorption is also calculated.     

Search for double- β decay processes in 108Cd and 114Cd with the help of the low-background CdWO 4 crystal scintillator

The lifetime of the recently discovered six-quasiparticle (6-qp) isomer in ¹⁴⁰Nd has been measured using the ¹²⁶Te(¹⁸O, 4n) reaction and the pulsed-beam technique at the Institut de Physique Nucléaire (IPN) Orsay. The deduced lifetime of the 6-qp isomer in ¹⁴⁰Nd of 1.23(7)μs supports the 20⁺ spin-parity assignment to the isomeric state which is based on a spherical configuration that coexists with the triaxial bands observed in this spin range. Evidence for delayed components for the transitions below the 19/2⁺ state in ¹³⁹Nd was observed, with an apparent half-life of 272(4)ns.     

Ground States of Quantum Antiferromagnets in Two Dimensions

We explore the ground states and quantum phase transitions of two-dimensional, spin S=1/2, antiferromagnets by generalizing lattice models and duality transforms introduced by Sachdev and Jalabert (1990, Mod. Phys. Lett. B4, 1043). The minimal model for square lattice antiferromagnets is a lattice discretization of the quantum nonlinear sigma model, along with Berry phases which impose quantization of spin. With full SU(2) spin rotation invariance, we find a magnetically ordered ground state with Néel order at weak coupling and a confining paramagnetic ground state with bond charge (e.g., spin Peierls) order at strong coupling. We study the mechanisms by which these two states are connected in intermediate coupling. We extend the minimal model to study different routes to fractionalization and deconfinement in the ground state, and also generalize it to cases with a uniaxial anisotropy (the spin symmetry groups is then U(1)). For the latter systems, fractionalization can appear by the pairing of vortices in the staggered spin order in the easy-plane; however, we argue that this route does not survive the restoration of SU(2) spin symmetry. For SU(2) invariant systems we study a separate route to fractionalization associated with the Higgs phase of a complex boson measuring noncollinear, spiral spin correlations: we present phase diagrams displaying competition between magnetic order, bond charge order, and fractionalization, and discuss the nature of the quantum transitions between the various states. A strong check on our methods is provided by their application to S=1/2 frustrated antiferromagnets in one dimension: here, our results are in complete accord with those obtained by bosonization and by the solution of integrable models.     

Spin-orbit-coupled dipolar Bose-Einstein condensates

We propose an experimental scheme to create spin-orbit coupling in spin-3 Cr atoms using Raman processes. By employing the linear Zeeman effect and optical Stark shift, two spin states within the ground electronic manifold are selected, which results in a pseudospin-1/2 model. We further study the ground state structures of a spin-orbit-coupled Cr condensate. We show that, in addition to the stripe structures induced by the spin-orbit coupling, the magnetic dipole-dipole interaction gives rise to the vortex phase, in which a spontaneous spin vortex is formed.     

Quantum Communication in Spin Chain with Multiple Spin Exchange Interaction

The transmission of quantum states in the anisotropic Heisenberg XXZ chain model with three-spin exchange interaction is studied. The average fidelity is used to evaluate the state transfer. It is found that quantum communication can be enhanced by the anisotropic coupling and multiple spin interaction. Such spin model can reduce the time required for the perfect state transmission where the fidelity is unity. The maximally entangled Bell states can be generated and separated from the whole quantum systems.     

Quantum simulation of classical thermal states

We establish a connection between ground states of local quantum Hamiltonians and thermal states of classical spin systems. For any discrete classical statistical mechanical model in any spatial dimension, we find an associated quantum state such that the reduced density operator behaves as the thermal state of the classical system. We show that all these quantum states are unique ground states of a universal 5-body local quantum Hamiltonian acting on a (polynomially enlarged) qubit system on a 2D lattice. The only free parameters of the quantum Hamiltonian are coupling strengths of two-body interactions, which allow one to choose the type and dimension of the classical model as well as the interaction strength and temperature. This opens the possibility to study and simulate classical spin models in arbitrary dimension using a 2D quantum system.     

New high spin level scheme of ~(87)Sr

High spin states of the odd-A87Sr were populated by the fusion-evaporation reaction82Se(9Be,4n)87Sr at a beam energy of 46 MeV. Excited levels of87 Sr have been extended up to an excitation energy of 7.4 MeV at spin31/2. The coupling of a g9/2neutron hole to the yrast states of the88 Sr core can account for the low-lying states in87 Sr. The structure of the higher spin states is discussed by analogy with those of the neighboring odd-A N =49isotones and possible configurations are proposed.     

Electronic quasiparticles and evolution of Fermi level spin states in thin magnetic layers

Here we report on high-resolution photoemission of iron layers grown on a W(1 1 0) substrate. The evolution of the substrate states upon sub-monolayer adsorption of Fe atoms leads to a shift in surface state binding energy. For thicker (1 1 0) films, sharp metallic surface states are obtained. Their dispersion displays the signature of quasiparticle renormalization due to dressing with excitations. The energy scale is characteristic for the spin wave spectrum in iron, thereby giving evidence of electron-magnon coupling. Furthermore, it is found that quantum well states occur as a function of layer thickness. These modify the spin density of states at the Fermi level in the ferromagnetic film.     

Zero-modes and thermodynamics of disordered spin-1/2 ladders

The influence of non-magnetic doping on the thermodynamic properties of two-leg S = 1/2 spin ladders is studied in this paper. It is shown that, for a weak interchain coupling, the problem can be mapped onto a model of random mass Dirac (Majorana) fermions. We investigate in detail the structure of the fermionic states localized at an individual mass kink (zero-modes) in the framework of a generalized Dirac model. The low-temperature thermodynamic properties are dominated by these zero-modes. We use the single-fermion density of states, known to exhibit the Dyson singularity in the zero-energy limit, to construct the thermodynamics of the spin ladder. In particular, we find that the magnetic susceptibility χ diverges at T → 0 as 1/T ln²(1/T), and the specific heat behaves as C 1/ln³(1/T). The predictions on magnetic susceptibility are consistent with the most recent results of quantum Monte Carlo simulations on doped ladders with randomly distributed impurities. We also calculate the average staggered magnetic susceptibility induced in the system by such defects.