共查询到20条相似文献,搜索用时 31 毫秒
1.
H. Kuratsuji R. Botet 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,49(1):111-116
We investigate a novel aspect of rotational tunneling of the macroscopic spin for multicomponent spinor Bose-Einstein condensate (BEC). The Lagrangian is deduced from
the multi-component BEC system formalism, and is written in terms of spin coherent states. From the effective Hamiltonian
for the collective spin, the tunneling rate is obtained through a functional integral of the spin variable. It is pointed
out that the cooperative effect between the Zeeman energy and the anisotropic nature of the spin-dependent inter-atomic interaction
plays a key role for occurrence of collective spin tunneling. 相似文献
2.
W.S. Chung 《Fortschritte der Physik》2014,62(8):619-625
A new kind of spin coherent state called a Z3‐graded spin coherent state is constructed by using the complex solution of the equation q3 = 1. We explicitly find three kinds of Z3‐graded spin coherent states. The associated coherent property and spin squeezing are also examined. 相似文献
3.
Z. Z. Cheng Bin Xu Z. M. Li Z. Cheng 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(3):289-294
In this paper, we discuss squeezed thermal spin states of magnons that are described by the Heisenberg Hamiltonian in the
ferromagnet, in which the magnon system possesses a new kind of quasiparticle, which we call ferromagnon, i.e. a “dressed”
quasi-particle obtained from the magnons by a Bogoliubov-Valatin transformation . Generally, the mass and noise properties
of ferromagnons possess potentially important and novel effects in condensed matter physics, which have extensive application
in the fields of science and technology. Moreover, it is convenient to introduce the Holstein-Primakoff method, in order to
take into account the nonlinear interaction among spin waves. At last we describe the quantum fluctuations of spin-components
in the squeezed thermal spin states of magnons and their temperature-dependence. Below some temperature, the squeezed thermal
spin states of ferromagnons show squeeze effect. 相似文献
4.
E. Guliyev F. Ertuğral A. A. Kuliev 《The European Physical Journal A - Hadrons and Nuclei》2006,27(3):313-320
In this study the scissors mode 1+ states are systematically investigated within the rotational invariant Quasiparticle Random Phase Approximation (QRPA) for
130-136Ba isotopes. We consider the 1+ vibrations generated by the isovector spin-spin interactions and the isoscalar and isovector quadrupole-type separable forces
restoring the broken symmetry by a deformed mean field according to A.A. Kuliev et al. (Int. J. Mod. Phys. E 9, 249 (2000)). It has been shown that the restoration of the broken rotational symmetry of the Hamiltonian essentially decreases
the B(M1) value of the low-lying 1+ states and increases the collectivization of the scissors mode excitations in the spectroscopic energy region. The agreement
between the calculated mean excitation energies as well as the summed B(M1) value of the scissors mode excitations and the available experimental data of 134Ba and 136Ba is rather good. A destructive interference between the orbit and spin part of the M1 strength has been found for barium isotopes near the shell closer. For all the nuclei under investigation, the low-lying
M1 transitions have ΔK = 1 character as it is the case for the well-deformed nuclei. 相似文献
5.
D.A. Garanin K. Kladko P. Fulde 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(2):293-300
We extend and apply a previously developed method for a semiclassical treatment of a system with large spin S. A multisite Heisenberg Hamiltonian is transformed into an effective classical Hamilton function which can be treated by
standard methods for classical systems. Quantum effects enter in form of multispin interactions in the Hamilton function. The latter is written in the form of an expansion in powers of J/(TS), where J is the coupling constant. Main ingredients of our method are spin coherent states and cumulants. Rules and diagrams are derived
for computing cumulants of groups of operators entering the Hamiltonian. The theory is illustrated by calculating the quantum
corrections to the free energy of a Heisenberg chain which were previously computed by a Wigner-Kirkwood expansion.
Received 5 May 1999 and received in final form 24 September 1999 相似文献
6.
Mario Bergeron 《Fortschritte der Physik》1992,40(2):119-159
Definition and formulas for harmonic oscillator coherent states and spin coherent states are reviewed in detail. The path integral formalism and its relation with the partition function of a system are also reviewed. The harmonic oscillator coherent state path integral is evaluated exactly at the discrete level and then used to find its continuum limit using various regularizations. The computation of the path integral for a particle of spin s put in a constant magnetic field is carried out using harmonic oscillator coherent states and spin coherent states, with a careful analysis of infinitesimal terms (in 1/N where N is the number of time slices) appearing in the Lagrangian. A mapping of the spin system into a CP1 model is shown explicitly. The theory of a spinless particle in the field of a magnetic monopole and its relation with the spin system are explained. The equivalence of these two models is established up to infinitesimal order by the introduction of an external field correction. This gives a new representation of a coherent state path integral in terms of a more familiar Feynman path integral. 相似文献
7.
P. A. Frigeri D. F. Agterberg I. Milat M. Sigrist 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,54(4):435-448
In materials without an inversion center of symmetry the spin
degeneracy of the conducting band is lifted by an antisymmetric
spin orbit coupling (ASOC). Under such circumstances, spin and
parity cannot be separately used to classify the Cooper pairing
states. Consequently, the superconducting order parameter is
generally a mixture of spin singlet and triplet pairing states. In
this paper we investigate the structure of the order parameter and
its response to disorder for the most symmetric pairing state
(A1). Using the example of the heavy Fermion superconductor
CePt3Si, we determine characteristic properties of the
superconducting instability. Depending on the type of the
pairing interaction, the gap function is characterized
by the presence of line nodes. We show that this line nodes move in general
upon temperature.
Such nodes would be essential to explain recent low-temperature
data of thermodynamic quantities such as the NMR-T1
-1,
London penetration depth, and heat conductance.
Moreover, we study the effect of (non-magnetic) impurity on the superconducting state. 相似文献
8.
The density functional theory method (DFT) (b3p86) of Gaussian 03 has been used to optimize the structure of the Mn2 molecule. The result shows that the ground state of the Mn2 molecule is an 11-multiple state, indicating a spin polarization effect in the Mn2 molecule, a transition metal element molecule. Meanwhile, we have not found any spin pollution because the wavefunction of the ground state does not mingle with wavefunctions of higher-energy states. So the ground state for Mn2 molecule being of an 11-multiple state is the indicative of spin polarization effect of the Mn2 molecule among those in the transition metal elements: that is, there are 10 parallel spin electrons in a Mn2 molecule. The number of non-conjugated electrons is the greatest. These electrons occupy different spacious orbitals so that the energy of the Mn2 molecule is minimized. It can be concluded that the effect of parallel spin in the Mn2 molecule is larger than the effect of the conjugated molecule, which is obviously related to the effect of electron d delocalization. In addition, the Murrell-Sorbie potential functions with the parameters for the ground state and other states of the Mn2 molecule are derived. The dissociation energy De for the ground state of the Mn2 molecule is 1.4477 eV, equilibrium bond length Re is 0.2506 nm, vibration frequency ωe is 211.51 cm^-1. Its force constants f2, f3, and f4 are 0.7240 aJ·nm-2, -3.35574 aJ·nm^-3, 11.4813 aJ·nm^-4 respectively. The other spectroscopic data for the ground state of the Mn2 molecule ωeχe, Be, αe are 1.5301 cm^-1, 0.0978 cm^-1, 7.7825×10^-4 cm^-1 respectively. 相似文献
9.
We study the interaction of many fields. We obtain an effective Hamiltonian for this system by using a method recently introduced that produces a small rotation to the Hamiltonian that allows to neglect some terms in the rotated Hamiltonian. We show that coherent states remain coherent under the action of a quadratic Hamiltonian and by solving the eigenvalue and eigenvector problem for tridiagonal matrices we also show that a system of n interacting harmonic oscillators, initially in coherent states, remain coherent during the interaction. 相似文献
10.
K.-V. Pham M. Gabay P. Lederer 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(4):573-576
Standard bosonization techniques lead to phonon-like excitations in a Luttinger liquid (LL), reflecting the absence of Landau
quasiparticles in these systems. Yet in addition to the above excitations some LL are known to possess solitonic states carrying
fractional quantum numbers (e.g. the spin 1/2 Heisenberg chain). We have reconsidered the zero modes in the low-energy spectrum of the Gaussian boson LL Hamiltonian
both for fermionic and bosonic LL: in the spinless case we find that two elementary excitations carrying fractional quantum
numbers allow to generate all the charge and current excited states of the LL. We explicitly compute the wavefunctions of
these two objects and show that one of them can be identified with the 1D version of the Laughlin quasiparticle introduced
in the context of the Fractional Quantum Hall effect. For bosons, the other quasiparticle corresponds to a spinon excitation.
The eigenfunctions of Wen's chiral LL Hamiltonian are also derived: they are quite simply the one dimensional restrictions
of the 2D bulk Laughlin wavefunctions.
Received 26 January 1999 and Received in final form 21 April 1999 相似文献
11.
This paper uses the density functional theory (DFT)(B3p86) of Gaussian03 to optimize the structure of Fe2 molecule. The result shows that the ground state for Fe2 molecule is a 9-multiple state, which shows spin polarization effect of Fe2 molecule of transition metal elements for the first time. Meanwhile, we have not found any spin pollution because the wavefunction of the ground state does not mingle with wavefunctions with higher energy states. So, that the ground state for Fe2 molecule is a 9-multiple state is indicative of the spin polarization effect of Fe2 molecule of transition metal elements. That is, there exist 8 parallel spin electrons. The non-conjugated electron is greatest in number. These electrons occupy different spacious tracks, so that the energy of the Fe2 molecule is minimized. It can be concluded that the effect of parallel spin of the Fe2 molecule is laFger than the effect of the conjugated molecule, which is obviously related to the effect of electron d delocalization. In addition, the Murrell Sorbie potential functions with the parameters for the ground state and other states of Fe2 molecule are derived. Dissociation energy De for the ground state of Fe2 molecule is 2.8586ev, equilibrium bond length Re is 0.2124nm, vibration frequency we is 336.38 cm^-1. Its force constants f2, f3, and f4 are 1.8615aJ.nm^-2, -8.6704aJ.nm^-3, 29.1676aj.nm^-4 respectively. The other spectroscopic data for the ground state of Fe2 molecule weXe, Be, αe are 1.5461 cm^-1, 0.1339cm^-1, 7.3428× 10^-4 cm^-1 respectively. 相似文献
12.
R. Safaiee M. M. Golshan 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,83(4):457-463
The present work is concerned with an analysis of the entanglement between the electronic
coherent superpositions of spin states and subbands in a
quasi-one-dimensional Rashba nanoloop acted upon by a strong perpendicular magnetic field.
We explicitly include the confining potential and the Rashba spin-orbit coupling into the
Hamiltonian and then proceed to calculate the von Neumann entropy, a measure of
entanglement, as a function of time. An analysis of the von Neumann entropy demonstrates
that, as expected, the dynamics of entanglement strongly depends upon the initial state
and electronic subband excitations. When the initial state is a pure one formed by a
subband excitation and the z-component of spin states, the entanglement exhibits periodic
oscillations with local minima (dips). On the other hand, when the initial state is formed
by the subband states and a coherent superposition of spin states, the
entanglement still periodically oscillates, exhibiting stronger correlations, along with
elimination of the dips. Moreover, in the long run, the entanglement for the latter case
undergoes the phenomenon of collapse-revivals. This behaviour is absent for the first case
of the initial states. We also show that the degree of entanglement strongly depends upon
the electronic subband excitations in both cases. 相似文献
13.
H.-y. Fan A. Wünsche 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,15(3):405-412
We examine the existence of right-hand eigenstates (or eigenkets) of the boson creation operator a
and determine their coordinate and their Bargmann representation. The eigenkets of the creation operator are ultrasingular
and cannot be considered as a limiting case of normalizable states. Applications of these eigenstates as auxiliary states
for purposes of representation of states by path integrals over coherent states are discussed. A completeness relation for
coherent states on paths through the complex plane is derived and special examples of its application are considered.
Received 9 March 2001 and Received in final form 13 June 2001 相似文献
14.
A two-dimensional tilted axis cranking Hartree-Fock-Bogoliubov (CHFB) calculation is performed for 76Kr and 78Kr nuclei up to high spins J = 30 employing a pairing-plus-quadrupole (PPQ) model interaction Hamiltonian. Intricate details of the evolution of single
particle structures and shapes as a function of spin have been investigated. The results show the existence of energy levels
with high K quantum numbers lying close to the yrast line in both the nuclei. Such high K states should exhibit isomeric characteristics due to the K-selection rules for the γ-decays. Moreover, in 78Kr a new band with J = 20–30 lying below the observed ground band is predicted.
相似文献
15.
The density functional theory (DFT) method (b3p86) of Gaussian 03 is used to optimize the structure of the Ni2 molecule. The result shows that the ground state for the Ni2 molecule is a 5-multiple state, symbolizing a spin polarization effect existing in the Ni2 molecule, a transition metal molecule, but no spin pollution is found because the wavefunction of the ground state does not mingle with wavefunctions of higher-energy states. So the ground state for Ni2 molecule, which is a 5-multiple state, is indicative of spin polarization effect of the Ni2 molecule, that is, there exist 4 parallel spin electrons in Ni2 molecule. The number of non-conjugated electrons is greatest. These electrons occupy different spatial orbitals so that the energy of the Ni2 molecule is minimized. It can be concluded that the effect of parallel spin in the Ni2 molecule is larger than that of the conjugated molecule, which is obviously related to the effect of electron d delocalization. In addition, the Murrell-Sorbie potential functions with the parameters of the ground state and other states of the Ni2 molecule are derived. The dissociation energy De for the ground state of the Ni2 molecule is 1.835 eV, equilibrium bond length Re is 0.2243 nm, vibration frequency we is 262.35 cm^-1. Its force constants f2, f3 and f4 are 1.1901 aJ.nm^-2, -5.8723 aJ.nm^-3, and 21.2505 aJ.nm^-4 respectively. The other spectroscopic data for the ground state of the Ni2 molecule ωeχe, Be and αe are 1.6315cm 2, 0.1141 cm^-1, and 8.0145× 10^-4 cm^-1 respectively. 相似文献
16.
The high spin yrast states uptoJ=22+ in182,184,186Os are studied in a microscopic variational approach with number-conserved projected states. The energy spectra, quadrupole,
moments andB (E2) values are calculated by employing the Hamiltonian with quadrupole plus pairing interactions. The results of the calculations
are in fair agreement with the available experimental data. 相似文献
17.
Exact solution of the one-dimensional spin-\frac{\mathsf 3}{\mathsf 2} Ising model in magnetic field
A. Avella F. Mancini 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,50(4):527-539
In this paper, we study the Ising model with general spin S in
presence of an external magnetic field by means of the equations of
motion method and of the Green's function formalism. First, the
model is shown to be isomorphic to a fermionic one constituted of
2S species of localized particles interacting via an intersite
Coulomb interaction. Then, an exact solution is found, for any
dimension, in terms of a finite, complete set of eigenoperators of
the latter Hamiltonian and of the corresponding eigenenergies. This
explicit knowledge makes possible writing exact expressions for the
corresponding Green's function and correlation functions, which turn
out to depend on a finite set of parameters to be self-consistently
determined. Finally, we present an original procedure, based on
algebraic constraints, to exactly fix these latter parameters in the
case of dimension 1 and spin
. For this latter case and,
just for comparison, for the cases of dimension 1 and spin
[F. Mancini, Eur. Phys. J. B 45, 497 (2005)] and
spin 1 [F. Mancini, Eur. Phys. J. B 47, 527 (2005)],
relevant properties such as magnetization 〈S 〉 and
square magnetic moment 〈S2 〉, susceptibility and
specific heat are reported as functions of temperature and external
magnetic field both for ferromagnetic and antiferromagnetic
couplings. It is worth noticing the use we made of composite
operators describing occupation transitions among the 3 species of
localized particles and the related study of single, double and
triple occupancy per site. 相似文献
18.
E. Arrigoni G.C. Strinati 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(3):433-448
We study the zero-temperature spin fluctuations of a two-dimensional itinerant-electron system with an incommensurate magnetic
ground state described by a single-band Hubbard Hamiltonian. We introduce the (broken-symmetry) magnetic phase at the mean-field
(Hartree-Fock) level through a spiral spin configuration with characteristic wave vector Q different in general from the antiferromagnetic wave vector Q
AF, and consider spin fluctuations over and above it within the electronic random-phase (RPA) approximation. We obtain a closed system of equations for the generalized wave vector and frequency dependent susceptibilities, which are equivalent to the
ones reported recently by Brenig. We obtain, in addition, analytic results for the spin-wave dispersion relation in the strong-coupling
limit of the Hubbard Hamiltonian and find that at finite doping the spin-wave dispersion relation has a hybrid form between that associated with the (localized) Heisenberg model and that associated with the (long-range) RKKY exchange interaction.
We also find an instability of the spin-wave spectrum in a finite region about the center of the Brillouin zone, which signals
a physical instability toward a different spin- or, possibly, charge-ordered phase, as, for example, the stripe structures
observed in the high-T
c materials. We expect, however, on physical grounds that for wave vectors external to this region the spin-wave spectrum that
we have determined should survive consideration of more sophisticated mean-field solutions.
Received 15 September 2000 相似文献
19.
Stefan K. Kehrein Andreas Mielke Peter Neu 《Zeitschrift für Physik B Condensed Matter》1995,99(1):269-280
Using continuous unitary transformations recently introduced by Wegner [1], we obtain flow equations for the parameters of
the spin-boson Hamiltonian. Interactions not contained in the original Hamiltonian are generated by this unitary transformation.
Within an approximation that neglects additional interactions quadratic in the bath operators, we can close the flow equations.
Applying this formalism to the case of Ohmic dissipation at zero temperature, we calculate the renormalized tunneling frequency.
We find a transition from an untrapped to trapped state at the critical coupling constant α
c
=1. We also obtain the static susceptibility via the equilibrium spin correlation function. Our results are both consistent
with results known from the Kondo problem and those obtained from mode-coupling theories. Using this formalism at finite temperature,
we find a transition from coherent to incoherent tunneling atT
2
*
≈2T
1
*
, whereT
1
*
is the crossover temperature of the dynamics known from the NIBA. 相似文献
20.
N. Veretenov Yu. Rozhdestvensky N. Rosanov V. Smirnov S. Fedorov 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(3):455-460
We propose the precision measurement of both angular rotation and of the gradient magnetic of a field based on the use of
matter wave interferometers with soliton states of a Bose-Einstein condensate (BEC). We consider the formation of these soliton
states in a BEC with negative scattering length by an optical lattice produced by two counterpropagating laser beams. We determine
the parameters of both the initial condensate and the optical radiation necessary for the formation of coherent solitons.
We demonstrate
that this interferometer can be used to measure magnetic field gradient with a precision of 10-2 pT/cm. Our calculations show that the sensitivity of a gyroscope based on a ring, two-port matter wave interferometer can
achieve 2.6×10-7 rad s-1. The precision of this method is more than ten times greater than in that of rotating interferometer with cooled atoms. 相似文献