共查询到20条相似文献，搜索用时 15 毫秒
1.
本文研究单分子磁体Na9[Cu3Na3(H2O)9 (α-AsW9O33)2]·26H2O中三角自旋 环在磁场作用下的热纠缠性质, 利用数值计算求出任意两个Cu2+离子量子比特之间的配对纠缠度, 分别记为C12, C23和C13. 研究结果表明, 磁场的方向和大小以及温度对配对纠缠度具有重要影响, 而且参数的变化对C12, C23和C13的影响也是各不相同. 给出外加三个不同方向的磁场时, 配对纠缠度C12, C23和C13各自对应的临界温度Tc随磁场强度的变化图, 由此可以得到单分子磁体三角自旋环中存在纠缠态的参数范围. 通过选择适当的磁场方向和大小以及温度等实验参数, 可以有效地调节和提高单分子磁体中的配对纠缠度.关键词：配对纠缠单分子磁体三角自旋环 相似文献
2.
Numerical study on tunneling splitting in biaxial spin systems is done by performing diagonalization of the Hamilton operator. It is found that the calculated energy splitting agrees quantitatively with theoretical prediction of instanton method. Our result shows that both the instanton method and the large spin limit work well for the total spin around 10. By including the fourth-order term in Hamiltonian, experimental observation can be re-covered quantitatively. 相似文献
3.
ZHANG Shu-Qun CHEN Zhi-De 《理论物理通讯》2008,50(7):248-252
Spin parity effect on magnetic relaxation by quantum tunneling in the biaxial spin model is studied by taking into account the transverse local stray field. It is shown that the square root time dependence in the even resonance occurs in the presence of a distribution of transverse anisotropic parameters, while the odd resonance always shows exponential relaxation. Magnetic relaxation under a sweeping field is also studied. The variation of the relaxation curve with the increasing distribution width of the local stray field for even resonance is qualitatively different from that of the odd resonance. The theoretical result on even resonance is in agreement with experimental results on Fe8 system, while the prediction for odd resonance awaits the experimental verification. 相似文献
4.
Spin parity effect on magnetic relaxation by quantum tunneling in the biaxial spin model is studied by taking into account the transverse local stray field. It is shown that the square root time dependence in the even resonance occurs in the presence of a distribution of transverse anisotropic parameters, while the odd resonance always shows exponential relaxation.Magnetic relaxation under a sweeping field is also studied. The variation of the relaxation curve with the increasing distribution width of the local stray field for even resonance is qualitatively different from that of the odd resonance. The theoretical result on even resonance is in agreement with experimental results onFe8 system, while the prediction for odd resonance awaits theexperimental verification. 相似文献
5.
本文研究了Na_9[Cu_3Na_3(H_2O)_9(α-As W_9O_(33))_2]·26H_2O(简记为{Cu_3})单分子磁体在热平衡和外加磁场作用下的三体纠缠性质,利用等效自旋模型和实验拟合参数,数值计算了{Cu_3}型三角自旋环中三体负性纠缠度(tripartite negativity).分别考虑沿垂直于三角自旋环方向的磁场、平行于三角自旋环方向的磁场,以及倾斜磁场的情形.结果表明,磁场的方向、大小以及温度对系统三体负性纠缠度有着重要影响.文中给出了在不同磁场方向下,临界温度随磁场强度的变化图,由此可以得到三体纠缠存在的参数区域.同时发现在特定的参数区域,该系统存在纠缠恢复现象.因此适当调节温度、磁场强度大小和磁场方向可以有效调控{Cu_3}型三角自旋环中的三体纠缠性质. 相似文献
6.
We have studied the quantum fluctuations of inelastic spin-electron scattering in quantum dot with an embedded biaxial single molecule-magnet and particularly investigated the zero-frequency shot noise and Fano factor in different magnetic fields. It is found that the shot noise and Fano factor exhibit a stepwise behaviour as bias increases in the presence of interaction between the electron and molecule-magnet for a weak magnetic field. As magnetic field becomes strong, a dip is displayed in the shot-noise-bias curve due to the suppression of inelastic shot noise caused by the quantum tunneling of magnetisation. Because of the spontaneous inelastic tunneling at zero bias, a small shot noise occurs, which results in the case of Fano factor F >> 1. Moreover, our results show that the sweeping speed can also influence the shot noise and Fano factor obviously. 相似文献
7.
8.
P. Thalmeier;P. Fulde 《Europhysics letters》1998,44(2):242-248
Recent X-ray analysis and NMR experiments have shown that is not a conventional spin-Peierls (SP)compound because above the transition at 33K it is in a homogeneousmixed valent (MV) state and atomic spin chains do notexist. Furthermore, thermal expansion experiments have identified theexistence of a double phase transition. We present a theoretical modelwhich qualitatively explains these observations. We derive aneffective Hamiltonian for the insulating state which describes thetransitions as primary charge order leading to linear spin chains inthe b -direction and a secondary SP transition. We show that thisscenario explains in a natural way the anomalous BCS ratio observedin .https://doi.org/10.1209/epl/i1998-00463-3 相似文献
9.
Within the framework of the effective-field theory with self-spin correlationsand the differential operator technique, the ground state magnetizations ofthe biaxial crystal field spin system on the honeycomb lattices have beenstudied. The influences of the biaxial crystal field on the magnetization inthe ground state have been investigated in detail. 相似文献
10.
C. F. Lo 《Il Nuovo Cimento D》1991,13(1):127-130
Summary We have investigated the ground state of a single hole in the half-filled Hubbard model on a 2D square lattice using the coupled-cluster
method. In particular we obtained an analytical expression of the hole energy dispersion function ɛ(k) which is consistent with earlier studies on thet-J model in the strong-coupling limit. An appreciable discrepancy on the hole energy bandwidth is, however, observed between
the Hubbard model and thet-J model. We believe that this discrepancy is due to the absence of the three-site interaction term in thet-J model. 相似文献
11.
通过分析不同温度下HgMnTe磁性二维电子气Shubnikov-de Hass（SdH）振荡的拍频现象,研究了量子阱中电子自旋 轨道相互作用和spd交换相互作用.结果表明：（1）在零磁场下,电子的自旋 轨道相互作用导致电子发生零场自旋分裂;（2）在弱磁场下,电子的自旋-轨道相互作用占主导地位,并受Landau分裂和Zeeman分裂的影响,电子的自旋分裂随磁场增加而减小;（3）在高磁场下,电子的spd交换相互作用达到饱和,电子的自旋分裂主要表现为Zeeman分裂.实验证明了当电子的Zeeman分裂能量与零场关键词：磁性二维电子气Zeeman分裂Rashba自旋分裂 相似文献
12.
《Europhysics letters》2011,96(1)
We show that in double-chain Mott insulators (ladders), disordered alternating ionic potentials may locally destroy coherence of magnetic excitations and lead to the appearance of spontaneously dimerized islands inside the Haldane spin-liquid phase. We argue that a boundary between the dimerized and Haldane phases of a spin-1/2 ladder supports a localized zero-energy Majorana fermion mode. Based on these findings we suggest a realization of a generalized Kitaev model where Majorana fermions can propagate in more than one dimension.https://doi.org/10.1209/0295-5075/96/17002 相似文献
13.
C. R. Becker K. Ortner X. C. Zhang A. Pfeuffer-Jeschke V. Latussek Y. S. Gui V. Daumer H. Buhmann G. Landwehr L. W. Molenkamp 《Physica E: Low-dimensional Systems and Nanostructures》2004,20(3-4):436
The band structure of HgTe quantum wells (QWs) has been determined from absorption experiments on superlattices in conjunction with calculations based on an 8×8 k·p model. The band structure combined with self-consistent Hartree calculations has enabled transport results to be quantitatively explained.Rashba spin–orbit, (SO) splitting has been investigated in n-type modulation doped HgTe QWs by means of Shubnikov–de Haas oscillations (SdH) in gated Hall bars. The heavy hole nature of the H1 conduction subband in QWs with an inverted band structure greatly enhances the Rashba SO splitting, with values up to 17 meV.By analyzing the SdH oscillations of a magnetic two-dimensional electron gas (2DEG) in modulation-doped n-type Hg1−xMnxTe QWs, we have been able to separate the gate voltage-dependent Rashba SO splitting from the temperature-dependent giant Zeeman splitting, which are of comparable magnitudes. In addition, hot electrons and Mn ions in a magnetic 2DEG have been investigated as a function of current.Nano-scale structures of lower dimensions are planned and experiments on sub-micrometer magneto-transport structures have resulted in the first evidence for ballistic transport in quasi-1D HgTe QW structures. 相似文献
14.
We consider a geometrically frustrated spin-(1/2) Ising-Heisenberg diamond chain, which is an exactly solvable model when assuming part of the exchange interactions as Heisenberg ones and another part as Ising ones. A small XY part is afterwards perturbatively added to the Ising couplings, which enabled us to derive an effective Hamiltonian describing the low-energy behavior of the modified but full quantum version of the initial model. The effective model is much simpler and free of frustration. It is shown that the XY part added to the originally Ising interaction gives rise to the spin-liquid phase with continuously varying magnetization, which emerges between the magnetization plateaus and is totally absent in the initial hybrid diamond-chain model. The elaborated approach can also be applied to other hybrid Ising-Heisenberg spin systems.https://doi.org/10.1209/0295-5075/112/37002 相似文献
15.
The spectrum of theB 2Σ-X 2Σ system of the CaF molecule has been photographed in the second order of a 10.6 m concave grating spectrograph with 0.33 Å/mm dispersion. The rotational structure of the (0, 0) and (1, 0) bands has been analysed and the precise molecular constants have been obtained. Using the constants so determined the band origins of a large number of bands with 0 <v′,v″ < 10 have been calculated and used to obtain the accurate vibrational constants forB andX states and these are presented. 相似文献
17.
Guo-Qiang Zhu 《Central European Journal of Physics》2009,7(1):135-140
We study the entanglement features of the ground state of a system composed of spin 1 and 1/2 parts. In the light of the ground state degeneracy, the notion of average entanglement is used to measure the entanglement of the Hilbert subspace. The entanglement properties of both a general superposition as well as the mixture of the degenerate ground states are discussed by means of average entanglement and the negativity respectively. 相似文献
18.
《Europhysics letters》2009,86(3)
We present a parent Hamiltonian for weakly dimerized valence bond solid states for arbitrary half-integral S . While the model reduces for to the Majumdar-Ghosh Hamiltonian, we discuss this model and its properties for . Its degenerate ground state is the most popular toy model state for discussing dimerization in spin 3/2 chains. In particular, it describes the impurity-induced dimer phase in Cr8Ni as proposed recently. We point out that the explicit construction of the Hamiltonian and its main features apply to arbitrary half-integral spin S .https://doi.org/10.1209/0295-5075/86/37005 相似文献
19.
K. Sheshadri;A. Chainani 《Europhysics letters》2013,104(2)
The family of cobaltates Ax CoO2 (A = Na, Li, K), with a crystal structure consisting of a layered triangular lattice of Co ions, exhibits a fascinating range of coupled spin, charge and ion ordering phenomena as a function of electron doping content x . Based on these experimental observations, we investigate an extended Ising model for suppression of magnetic frustration caused by electron doping in a quasi–2-dimensional nearest-neighbour antiferromagnetic triangular lattice. As determined by geometry and bond-counting, it is found that magnetic frustration can be quantified by a frustration index f ub and its magnitude is a non-monotonic function of x . A mean-field calculation is carried out to determine the temperature-dependent magnetization, spin-entropy and heat capacity for the obtained structures with the lowest energy (≡ lowest f ub ) for each x . The calculations reveal that the magnetic-ordering temperature T C exhibits an anti-correlation with f ub as a function of x . In addition, as seen in thermopower experiments, an anomalous spin-entropy is obtained for the high-doping cases when . The results indicate the importance of doping-dependent magnetic frustration in the layered cobaltates.https://doi.org/10.1209/0295-5075/104/27007 相似文献