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1.
H.-A. Krug von Nidda N. Büttgen A. Loidl 《The European physical journal. Special topics》2009,180(1):161-189
The present understanding of quantum spin chains is reviewed from the magnetic resonance point of view. This includes both
the ideal one-dimensional properties in the spin sector as well as the complex interplay with orbital, charge, and lattice
degrees of freedom which govern the ground state. In copper-phosphates we observe an extremely extended paramagnetic regime
governed by strong antiferromagnetic correlations with record values of the ratio kBTN/J < 6×10−4, which compares the ordering temperature of a Néel state to the magnitude of the exchange J between neighbouring spins. A
detailed quantitative discussion of NMR and ESR relaxation within this paramagnetic regime elucidates the relevant exchange
interactions in typical bonding geometries of most common quantum-spin-chain systems like KCuF3, CuGeO3, NaxV2O5, and LiCuVO4. Concerning the ground state, paramount topics of modern solid-state physics arise among these examples as there are multiferroicity,
charge order, metal-insulator transition, and spin dimerization as well as phase separation. 相似文献
2.
Vladyslav O. Cheranovskii Elena V. EzerskayaDouglas J. Klein Aleksei A. Kravchenko 《Journal of magnetism and magnetic materials》2011,323(12):1636-1642
The spin model of “ferrimagnetic” nanotube is proposed and some theoretical predictions concerning the ground state and low energy excitations of the model are given. In particular, the spin-wave structure of the exact ground state of bipartite magnets is proven. For tubes formed by weakly interacted cyclic fragments we show: first, the existence of gapless excitations with decreasing total spin; and second, gapped excitations. This leads to an intermediate plateau in field dependence of tube magnetization. Numerical calculations show the strong effect of frustrations on the magnetization of anisotropic spin tubes at low temperatures which may lead to the creation of an additional fractional magnetization plateau. 相似文献
3.
E. Rastelli A. Tassi 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(3):341-347
Ferromagnetic spin chains of a hexagonal lattice coupled by a weak antiferromagnetic interaction J1 develop a helix arrangement if the intrachain antiferromagnetic NNN exchange J2 is sufficiently large. We show that the classical minimum energy spin configuration is an umbrella when an external magnetic field is applied. The scenario is dramatically changed by quantum fluctuations. Indeed we find
that the zero point motion forces the spins in a plane containing the magnetic field so that classical expectation is deceptive
for our model. Our result is obtained by controlled expansion in the low field-long wavelength modulation limit.
Received: 9 September 1997 / Revised: 15 October 1997 / Accepted: 17 November 1997 相似文献
4.
Paolasini L Ouladdiaf B Bernhoeft N Sanchez JP Vulliet P Lander GH Canfield P 《Physical review letters》2003,90(5):057201
A combination of neutron elastic and inelastic, resonant x-ray scattering, and 57Fe M?ssbauer experiments are used to determine the unusual magnetic ground state of CeFe2. The complementarities between different time-scale techniques may allow one to understand the dynamic features of the ground state in CeFe2 and its pseudobinary compounds, and how the frustration of Fe tetrahedra leads the appearance of antiferromagnetic fluctuations in the presence of ferrimagnetism. The resulting model can be used to rationalize many of the unusual and conflicting experimental results reported for this material in the literature. 相似文献
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《Nuclear Physics B》1998,516(3):603-622
The integrable open-boundary conditions for the model of three coupled one-dimensional XY spin chains are considered in the framework of the quantum inverse scattering method. The diagonal boundary K-matrices are found and a class of integrable boundary terms is determined. The boundary model Hamiltonian is solved by using the coordinate space Bethe ansatz technique and Bethe ansatz equations are derived. 相似文献
8.
E. I. Golovenchits V. A. Sanina A. A. Levin Yu. I. Smolin Yu. F. Shepelev 《Physics of the Solid State》1997,39(9):1425-1432
Local ion displacements and their anharmonicity in Eu2CuO4 and La2CuO4 crystals are studied by high-precision x-ray diffractometry. A symmetry analysis and the temperature behavior of the probability
density function of Cu2+ ions reveal a degenerate ground orbital state in the Eu2CuO4 crystal (tetragonal doublet d
xz, d
yz). The pattern and anharmonicity of the local displacements are found to be determined not only by lattice vibrations but
by 2D antiferromagnetic spin fluctuations in the CuO2 sheet as well. By contrast, in the La2CuO4 crystal the orbital ground state of the Cu2+ ion is a singlet (d
z
2). The pattern of Eu3+ local displacements and their effect on the properties of the Cu subsystem in the Eu2CuO4 crystal are also studied.
Fiz. Tverd. Tela (St. Petersburg) 39, 1600–1608 (September 1997) 相似文献
9.
K. Totsuka 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):705-717
Novel massive quantum states appearing in spin chains under a strong magnetic field are discussed. These states lead to plateaus in magnetization
curves. When the systems are axially symmetric and the field is applied parallel to the symmetry-axis, the phenomena are analogous
to metal-insulator transitions. Striking features of the plateau phenomena - exactness and rationality - are explained as
consequences the commensurability condition to the underlying lattice. The effects of the planar anisotropy are also discussed
in detail.
Received: 16 February 1998 / Revised: 20 April 1998 / Accepted: 30 April 1998 相似文献
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Yao NY Jiang L Gorshkov AV Gong ZX Zhai A Duan LM Lukin MD 《Physical review letters》2011,106(4):040505
We propose and analyze a new approach for quantum state transfer between remote spin qubits. Specifically, we demonstrate that coherent quantum coupling between remote qubits can be achieved via certain classes of random, unpolarized (infinite temperature) spin chains. Our method is robust to coupling-strength disorder and does not require manipulation or control over individual spins. In principle, it can be used to attain perfect state transfer over an arbitrarily long range via purely Hamiltonian evolution and may be particularly applicable in a solid-state quantum information processor. As an example, we demonstrate that it can be used to attain strong coherent coupling between nitrogen-vacancy centers separated by micrometer distances at room temperature. Realistic imperfections and decoherence effects are analyzed. 相似文献
12.
Huang SW Huang DJ Okamoto J Mou CY Wu WB Yeh KW Chen CL Wu MK Hsu HC Chou FC Chen CT 《Physical review letters》2008,101(7):077205
Based on resonant soft x-ray magnetic scattering, we report that LiCu2O2 exhibits a large interchain coupling which suppresses quantum fluctuations along spin chains, and a quasi-2D short-range magnetic order prevails at temperatures above the magnetic transition. These observations unravel the fact that the ground state of LiCu2O2 possesses long-range 2D-like incommensurate magnetic order rather than being a gapped spin liquid as expected from the nature of quantum spin-1/2 chains. In addition, the spin coupling along the c axis is found to be essential for inducing electric polarization. 相似文献
13.
We rigorously rule out the appearance of multiple domain walls between ground states in 2D Edwards-Anderson Ising spin glasses (with periodic boundary conditions and, e.g., Gaussian couplings). This supports the conjecture that there is only a single pair of ground states in these models. 相似文献
14.
J. Q. Ma A. M. Wang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2012,66(1):6
We study the transfer of an arbitrary two-qubit pure state with the spin-chain channels
and analyze the relevant influences from one common spin environment, asynchronous
measurements and imperfect initialization. Since it is not satisfactory enough by directly
extending Bose’s transfer scheme, we propose and develop an improved dual-rail channel by
using two pairs of inhomogenous spin chains one of which is auxiliary. Our results show
that the improved scheme can achieve the perfect transfer and greater success probability
in a longer distance. In particular, we calculate different influences of the spin
environment on different spin-chain channels, and figure out that success probability is
not seriously affected by asynchronous measurements, as long as the difference of
measurement times on two auxiliary spin chains is small enough. Moreover, the general
expression of success probability is also given in the influence of imperfect
initialization when the transfer is perfect. 相似文献
15.
X. Q. Xi J. B. Gong T. Zhang R. H. Yue W. M. Liu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,49(2):193-199
For the process of electron-electron (e-e) bremsstrahlung the momentum and energy distributions of the recoiling electrons
are calculated in the laboratory frame. In order to get the differential cross section and the photon spectrum for target
electrons which are bound to an atom, these formulae are multiplied by the incoherent scattering function and numerically
integrated over the recoil energy. The effect of atomic binding is most pronounced at low energies of the incident electrons
and for target atoms of high atomic numbers. The results are compared to those of previous calculations. 相似文献
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本文采用六带K·P理论计算了耦合量子点在不同耦合距离下空穴基态特性, 探讨了轻重空穴及轨道自旋相互作用对耦合量子点空穴基态反成键态特性的影响. 在考虑多带耦合的情况下, 耦合量子点随着耦合强度的变化, 价带基态能级和激发态能级发生反交叉现象. 同时, 随着耦合距离的增加, 量子点基态轻重空穴波函数的比重发生变化,导致量子点空穴基态波函数从成键态反转成为反成键态. 同时研究发现, 因空穴基态及激发态波函数特性的转变, 电子、空穴的基态及激发态波函数的叠加强度发生的明显变化.
关键词:
耦合量子点
反键态
多带理论
自旋轨道耦合 相似文献
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Low-energy spin excitations of La(1.85)Sr(0.15)Cu(1-y)Zn(y)O4 were studied by neutron scattering. In y=0.004, the incommensurate magnetic peaks show a well-defined "spin gap" below T(c). The magnetic signals at omega=3 meV decrease below T(c)=27 K for y=0.008, also suggesting the gap opening. At lower temperatures, however, the signal increases again, implying a novel in-gap spin state. In y=0.017, the spin gap vanishes and elastic magnetic peaks appear. These results clarify that doped Zn impurities induce the novel in-gap state, which becomes larger and more static with increasing Zn. 相似文献