共查询到20条相似文献,搜索用时 31 毫秒
1.
V. A. Kartoshkin 《Optics and Spectroscopy》2011,110(5):665-671
The interaction of alkali K and Rb atoms that reside in the ground state is considered in the range of collision energies
E = 10−4 to 10−2 au. The singlet (X
1Σ+) and triplet (a
3Σ+) interaction potentials available in the literature are analyzed and modified. For the KRb dimer in the range of interatomic
distances 15–21a
0, we chose analytical representations of the singlet and triplet potentials that more accurately describe the interaction
of alkali Rb and K atoms in the ground state. Complex cross sections of the spin exchange are calculated for the first time
that permit one to calculate the processes of polarization transfer and relaxation times, as well as shifts in the magnetic
resonance frequencies caused by K-Rb spin exchange collisions. 相似文献
2.
F. A.B.F. de Moura 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(4):389-393
In this work, a one-dimensional quantum Heisenberg ferromagnet with aperiodic exchange couplings is considered. To produce
an aperiodic distribution of exchange couplings, it is used a sinusoidal function whose phase φ varies as a power-law, φ∝nν, where n labels the positions along the chain. By using exact diagonalization, the spin-wave participation number and the
local density of states are computed. The numerical calculations
indicate that for 0 < ν < 1, this ferromagnetic system displays a phase
of extended spin waves in the low-energy region. For ν > 1
all spin waves are localized except for the zero energy mode. By integrating the time-dependent Schr?dinger equation, the
temporal evolution of the mean-square displacement of the wave-packet was followed. Associated with the emergence of extended
spin waves, it was observed that the wave-packet mean-square displacement displays a ballistic spread. 相似文献
3.
We use the spin non-degenerate single impurity Anderson model to investigate the influence of the local spin polarization
to the Kondo effect. By using the Schrieffer-Wolff transformation, we obtain a generalized s-d exchange Hamiltonian, which
describes the interaction between a polarized local spin and conduction electrons. In this case, the singlet is no longer
an eigenstate as shown by variational calculations where the splitting of the local energy Δ = ɛ
d↑ − ɛ
d↓ can be arbitrarily small. The local spin polarization generates the instability of the singlet ground state of the S = 1/2 s-d exchange model.
相似文献
4.
Masayoshi Senba 《Hyperfine Interactions》1991,65(1-4):779-791
The spin dynamics of the positive muon undergoing cyclic charge exchange (μ+⇌Mu) while it is slowing down is compared with that in the case of repeated muonium spin exchange after thermalization. The
expectation value of the spin polarization at timet aftern spin exchange collisions (att
1,t
2, ...,t
n
) are calculated explicitly from time dependent wave functions, and the quantity is averaged over the statistical distribution
of the times of collisions and over all possible numbers of collisions betweent=0 and the observation timet. This result is complementary and equivalent to the conventional density matrix formalism, but offers an insight into the
roles of spin flip and spin non-flip processes. The neutral fraction during slowing down is also discussed. 相似文献
5.
The recent neutron scattering data for spin-wave dispersion in HoMnO3 are well-described by an anisotropic Hubbard model on a triangular lattice with a planar (XY) spin anisotropy. Best fit indicates
that magnetic excitations in HoMnO3 correspond to the strong-coupling limit U/t >∼ 15, with planar exchange energy J = 4t
2
/U ≃ 2.5 meV and planar anisotropy ΔU ≃ 0.35 meV.
相似文献
6.
S. P. Mukherjee 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,80(1):51-58
Helical edge states exist in the mixed spin-singlet and spin-triplet phase of a noncentrosymmetric (NCS) superconductor [Y.
Tanaka, T. Yokoyama, A.V. Balatsky, N. Nagaosa, Phys. Rev. B 79, 060505(R) (2009)]. In this article we have considered a planar ferromagnetic metal/NCS superconductor tunnel junction and
have studied the effect of these helical edge states which manifests itself through the charge and spin tunneling conductance
across the junction. We have shown the behavior of conductance for the entire range of variation of γ = Δ
-/Δ
+ where Δ
± are the order parameters in the
positive and negative helicity bands of the NCS superconductor. There exists a competition between the Rashba parameter α and the exchange energy E
ex
which is crucial for
determining the variation of the conductance with the applied bias voltage across the junction. We have found a nonzero spin
current across the junction which appears due to the
exchange energy in the Ferromagnet and modulates with the bias voltage. It also changes its profile when the strength of the
exchange energy is varied. 相似文献
7.
W. Li Z. Zhang P. Tong 《The European Physical Journal B - Condensed Matter and Complex Systems》2012,85(2):73
The effect of the Dzyaloshinskii-Moriya (DM) interaction on the heat conduction in the quantum Ising chain has been studied
by solving the Lindblad master equation. The chain is subject to a uniform transverse field h, while the exchange couplings {J
m
} between the nearest-neighbor spins are either uniform, random or quasi-periodic. The average energy-density profile and
the average energy current in the non-equilibrium steady state have been numerically calculated. The ballistic transport is
observed in the uniform Ising chain with DM interaction. For the random Ising chain with DM interaction, the energy gradient
is observed in the bulk of the spin chain whose energy current appears to scale as the system size ⟨Q⟩ ∼ exp(βN) with β < 0. For the quasi-periodic Ising chain with DM interaction, the J
m
takes the two values J
A
and J
B
arranged in the Fibonacci sequence. The energy gradient also exists in the spin chain and the energy current behaves as ⟨Q⟩ ∼ N
α
with α < 0. By increasing the strength of the DM interaction D, a non-trivial transition from the thermal insulator heat transport to anomalous heat conduction is found in the Fibonacci
Ising chain with large ratio of couplings λ = J
A
/J
B
. A rough phase diagram of λ vs. D is given in this paper as well. 相似文献
8.
K.C. Chung C.S. Wang A.J. Santiago J.W. Zhang 《The European Physical Journal A - Hadrons and Nuclei》2001,11(2):137-141
The σ-ω coupling is introduced phenomenologically in the linear σ-ω model to study the nuclear matter properties. It is shown
that not only the effective nucleon mass M* but also the effective σ meson mass m
σ
* and the effective ω meson mass m
ω
* are nucleon-density-dependent. When the model parameters are fitted to the nuclear saturation point, with the nuclear radius
constant r
0 = 1.14 fm and volume energy a
1 = 16.0 MeV, as well as to the effective nucleon mass M
* = 0.85M, the model yields m
σ
* = 1.09m
σ and m
ω
* = 0.90m
ω at the saturation point, and the nuclear incompressibility K
0 = 501 MeV. The lowest value of K0 given by this model by adjusting the model parameters is around 227 MeV.
Received: 23 March 2001 / Accepted: 8 June 2001 相似文献
9.
Masayoshi Senba Alicia C. Gonzalez James R. Kempton Donald J. Arseneau James J. Pan Alexandra Tempelmann Donald G. Fleming 《Hyperfine Interactions》1991,65(1-4):979-986
The addition reaction Mu+NO+M→MuNO+M and the spin exchange reaction Mu(↑) +MO(↓)→Mu(↓)+NO(↑) have been measured by longitudinal
field μSR at room temperature in the presence of up to 58 atm of N2 as inert collider. The pressure dependence of the longitudinal relaxation rate due to the addition reaction (λc) demostrates that the system is still in the low pressure regime in this pressure range. The corresponding termolecular rate
constant has been determined ask
0,Mu
=(1.10±0.25)×10−32 cm6 molecules−2 s−1, almost 4 times smaller than the corresponding H atom reactionk
0,H=3.90×10−32 cm6 molecules−2 s−1 [I.M. Campbell et al., J. Chem. Soc. Faraday Trans. 1.71 (1975) 2097]. The average value of the spin exchange rate constants
in the 2.5–58 atm pressure range,k
SE=(3.16±0.06)×10−10 cm3 molecule−1 s−1, is in good agreement with previous values obtained by transverse field μSR [D.G. Fleming et al., J. Chem. Phys. 73 (1980)
2751]. 相似文献
10.
S. S. Aplesnin 《Physics of the Solid State》1998,40(6):986-990
An analysis is made of the two-dimensional Heisenberg model with S=1/2, anisotropic exchange interaction between nearest neighbors, and alternating exchange in two directions, [100] and [010]
(corresponding to condensation of the (π, π) mode) and in one direction [100] (corresponding to condensation of the (π, 0) mode). The quantum Monte Carlo method is used to calculate the thermodynamic characteristics and the spin correlation
functions which are used as the basis to determine the boundary of stability of an anisotropic antiferromagnetic with respect
to alternation of exchange δ=(1−J
x,y
/J
z
)0.4 in the (π,π) model and δ=(1−J
x,y
/J
z
)0.31 in the (π,0) model. In the (π,0) model a disordered quantum state exists in the range (1−J
x,y
/J
z
)0.31<δ<(0.3–0.35). The energy (E−0.68)=0.36δ
1.80(6) and 0.21 δ
2.0(5), the energy gap between the ground and excited states H
c
(δ)=1.96δ
2.(1), 1.8(1) (δ−0.35(3))0.67(2) were determined as a function of the alternation of exchange in the (π,π)-and (π,0) models, respectively.
Fiz. Tverd. Tela (St. Petersburg) 40, 1080–1085 (June 1998) 相似文献
11.
A. I. Reznikov S. Ya. Umanskii Yu. F. Chaikina 《Russian Journal of Physical Chemistry B, Focus on Physics》2010,4(2):203-209
Rate constants for electron-vibrational energy exchange Ar(3
P
2) + N2(X
1Σ
g
+, ν = 0) → Ar(1
S
0) + N2(C
3Π
u
, ν′), where ν′ = 0, 1, 2, were calculated. Calculations were performed taking into account the presence of a resonance in electron scattering
by N2(X
1Σ
g
+). As a result, the interaction of Ar(3
P
2) with N2(X
1Σ
g
+, ν = 0) was characterized by attraction and, in the end, intersection of electron-vibrational potential surfaces correlating
with Ar(3
P
2) + N2(X
1Σ
g
+, ν = 0) and Ar(1
S
0) + N2(C
3Π
u
, ν′) at interparticle distances of 2.5–3.5 ?. Exchange interaction at which electron-vibrational transitions in the region of
intersection of electron-vibrational transitions in the region of intersection of electron-vibrational potential surfaces
accompanied by spin exchange were induced was calculated by the asymptotic method. The rate constants determined at 300–600
K were on the order of 10−11−10−12 cm3/s and weakly increased as the temperature grew. Mainly the C
3Π
u
, ν′ = 0 state of the N2 molecule was populated. The calculation results were in satisfactory agreement with the experimental data obtained at 300
K. 相似文献
12.
Tumpa Bhattacharjee 《Pramana》2010,75(1):25-38
The variety of shapes and structures, observed in light rare earth A ∼ 130 nuclei, have been discussed in view of different angular momentum coupling schemes and their interplay that comes into
effect at high spin. The N = 79 and 80 isotopes in La-Ce region, produced via fusion evaporation reaction, have been studied using the Indian National
Gamma Array (INGA) consisting of 18 clover HPGe detectors. Two nearly degenerate ΔI = 1 bands have been observed at high spin of 137Ce and a triaxial deformation of γ = ±30° has been assigned to the bands, from the total Routhian surface (TRS) calculations. The high-spin candidates of the
yrast band of 138Ce show signature splitting both in energy and B(M1)/B(E2) values. The bandcrossing due to the alignment of a pair of h
11/2 proton particles has been conjectured at ℏω ∼ 0.3 MeV, from the single-particle Routhians obtained from TRS calculations. Lifetime measurements by Doppler shift attenuation
method (DSAM) has been carried out and from the estimated reduced transition probability B(M1), the ΔI = 1 band in 138Ce has been characterized as a magnetic rotation (MR) band. The rise in the values of B(M1), for the higher spin candidates of the band, has been conjectured as the reopening of a different shear at the top of the
Band B1. The characteristic of the MR bands in A ∼ 130 region has been discussed in the light of a phenomenological calculation and compared to the MR bands in other mass
regions. 相似文献
13.
L Satpathy 《Pramana》1989,32(4):319-330
The ground-state energy of an atomic nucleus with asymmetryβ is considered to be equivalent to the energy of a perfect sphere made up of the infinite nuclear matter of the same asymmetry
plus a residual energyη called the local energy,η represents the energy due to shell, deformation, diffuseness and exchange Coulomb effect etc. Using this picture and the
generalized Hugenholtz- Van Hove theorem of many-body theory a new mass formula has been developed. Based on this, a mass
table containing the mass excesses of 3481 nuclei in the range 18 ⩽A ⩽ 267 has been made. This mass formula is compared with other mass models. 相似文献
14.
S. Wolf V. Lisin R. Kondratiev A.M. Massone G. Galler J. Ahrens H.-J. Arends R. Beck M. Camen G.P. Capitani P. Grabmayr F. Härter T. Hehl P. Jennewein K. Kossert A.I. L'vov C. Molinari P. Ottonello R.O. Owens J. Peise I. Preobrajenskij S. Proff A. Robbiano M. Sanzone M. Schumacher M. Schmitz F. Wissmann 《The European Physical Journal A - Hadrons and Nuclei》2001,12(2):231-252
15.
M. Babamoradi M. Heidari Saani A. Ranjbar M. A. Vesaghi Y. Kawazoe 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,84(1):1-9
Using a generalized Hubbard Hamiltonian, many-electron wavefunctions of negatively
charged (NV−) and neutral nitrogen-vacancy (NV0) centers in diamond
were calculated. We report the effect of symmetric relaxation of surrounding atoms on the
spin density, calculated from the many electron wavefunctions in the ground and excited
states. We evaluated the error, that, arises in estimation of spin density when lattice
relaxation effect is neglected in Electron Paramagnetic Resonance experiment and showed
that the ground state spin density distribution is accessible in outward relaxations. The
computed oscillator strengths give a higher efficiency for the 1.945 eV photoluminescence
(PL) line of NV− with respect to 2.156 eV PL line of NV0 which
agrees well with experiment. This result is explained based on the largest the ground
state spin among available values for the NV− with respect to NV0.
The transition probability between degenerate ground and excited states slightly depends
on the S
z
value. Finally, we report on the
electronic configurations which contribute to the ground and excited states and discuss
the population variation of electronic configurations with relaxation. 相似文献
16.
Pion mass and its decay constant have been studied in a chiral symmetric potential model of independent quarks. The non-perturbative
multi-gluon interaction which is responsible for quark confinement in a hadron is phenomenologically represented here by an
effective potentialU(r) = 1/2(1 +γ
0)(ar
2 +V
0). The residual interactions due to quark-pion coupling arising out of the chiral symmetry preservation and that due to quark-gluon
coupling arising out of single-gluon exchange are treated as low order perturbations. The centre of mass correction is also
taken into account appropriately. This leads to the
mass in consistency with that of the PCAC-pion and the pion decay constant in reasonable agreement with experiment. 相似文献
17.
V. I. Ritus 《Journal of Experimental and Theoretical Physics》2006,102(4):582-602
The symmetry manifests itself in exact relations between the Bogoliubov coefficients for processes induced by an accelerated
point mirror in 1 + 1 dimensional space and the current (charge) densities for the processes caused by an accelerated point
charge in 3 + 1 dimensional space. The spectra of pairs of Bose (Fermi) massless quanta emitted by the mirror coincide with
the spectra of photons (scalar quanta) emitted by the electric (scalar) charge up to the factor e
2/ħc. The integral relation between the propagator of a pair of oppositely directed massless particles in 1 + 1 dimensional space
and the propagator of a single particle in 3 + 1 dimensional space leads to the equality of the vacuum-vacuum amplitudes for
the charge and the mirror if the mean number of created particles is small and the charge e = √ħc. Due to the symmetry, the mass shifts of electric and scalar charges (the sources of Bose fields with spin 1 and 0 in 3 +
1 dimensional space) for the trajectories with a subluminal relative velocity β12 of the ends and the maximum proper acceleration w
0 are expressed in terms of the heat capacity (or energy) spectral densities of Bose and Fermi gases of massless particles
with the temperature w
0/2π in 1 + 1 dimensional space. Thus, the acceleration excites 1-dimensional oscillation in the proper field of a charge,
and the energy of oscillation is partly deexcited in the form of real quanta and partly remains in the field. As a result,
the mass shift of an accelerated electric charge is nonzero and negative, while that of a scalar charge is zero. The symmetry
is extended to the mirror and charge interactions with the fields carrying spacelike momenta and defining the Bogoliubov coefficients
αB,F. The traces trαB,F, which describe the vector and scalar interactions of the accelerated mirror with a uniformly moving detector, were found
in analytic form for two mirror trajectories with subluminal velocities of the ends. The symmetry predicts one and the same
value e
0
= √ħc for the electric and scalar charges in 3 + 1 dimensional space. Arguments are adduced in favor of the conclusion that this
value and the corresponding value α0 = 1/4π of the fine structure constant are the bare, nonrenormalized values.
The text was submitted by the author in English. 相似文献
18.
Michael O’Carroll 《Journal of statistical physics》2012,146(4):864-869
We consider general d-dimensional lattice ferromagnetic spin systems with nearest neighbor interactions in the high temperature region (β≪1). Each model is characterized by a single site apriori spin distribution taken to be even. We also take the parameter α=〈s
4〉−3〈s
2〉2>0, i.e. in the region which we call Gaussian subjugation, where 〈s
k
〉 denotes the kth moment of the apriori distribution. Associated with the model is a lattice quantum field theory known to contain a particle
of asymptotic mass −lnβ and a bound state below the two-particle threshold. We develop a β analytic perturbation theory for the binding energy of this bound state. As a key ingredient in obtaining our result we show
that the Fourier transform of the two-point function is a meromorphic function, with a simple pole, in a suitable complex
spectral parameter and the coefficients of its Laurent expansion are analytic in β. 相似文献
19.
B. Canals D.A. Garanin 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(4):439-447
Thermodynamic quantities and correlation functions (CFs) of the classical antiferromagnet on the checkerboard lattice are
studied for the exactly solvable infinite-component spin-vector model, D↦∞. In contrast to conventional two-dimensional magnets with continuous symmetry showing extended short-range order at distances
smaller than the correlation length, r
ξ
c∝ exp(T
*/T), correlations in the checkerboard-lattice model decay already at the scale of the lattice spacing due to the strong degeneracy
of the ground state characterized by a macroscopic number of strongly fluctuating local degrees of freedom. At low temperatures,
spin CFs decay as <
>∝ 1/r
2 in the range a
0≪r≪ξ
c∝T
-1/2, where a0 is the lattice spacing. Analytical results for the principal thermodynamic quantities in our model are very similar with
MC simulations, exact and analytical results for the classical Heisenberg model (D = 3) on the pyrochlore lattice. This shows that the ground state of the infinite-component spin vector model on the checkerboard
lattice is a classical spin liquid.
Received 16 November 2001 and Received in final form 12 February 2002 相似文献
20.
Yu. A. Troyan S. G. Arakelyan A. V. Belyaev A. P. Ierusalimov E. B. Plekhanov A. Yu. Troyan 《Physics of Particles and Nuclei Letters》2011,8(6):557-561
The results of a search for and study of the scalar 0+ [0++] σ0 mesons in a π+π− system produced in the reaction np → npπ+π− at the quasi-monochromatic neutron beam momentum P
n
= (3.83 ± 0.12) GeV/c are presented as derived from analyzing the data obtained during the exposure of a 1-meter hydrogen bubble chamber at the
Laboratory of High Energy, Joint Institute for Nuclear Research (LHE JINR). It is found that there is a significant bump in
the effective mass distribution at Mp+ p- = (404 ±5)MeV/c2M_{\pi ^ + \pi ^ - } = (404 \pm 5)MeV/c^2 and Γresexp = (14±5.4) MeV/c
2, which is observed with more than four standard deviations from the background. The spin of this resonance is estimated to
be most likely equal to zero. Its quantum numbers are found to be 0+ [0++]. 相似文献