共查询到20条相似文献,搜索用时 46 毫秒
1.
T. Bergmann M. DeKieviet T. Gasenzer O. Nachtmann M.-I. Trappe 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(3):551-574
We discuss the propagation of hydrogen atoms in static electric and magnetic fields in a longitudinal atomic beam spin echo
(lABSE) apparatus. There the atoms acquire geometric (Berry) phases that exhibit a new manifestation of parity-(P-)violation
in atomic physics. We provide analytical as well as numerical calculations of the behaviour of the metastable 2S states of
hydrogen. The conditions for electromagnetic field configurations that allow for adiabatic evolution of the relevant atomic
states are investigated. Our results provide the theoretical basis for the discussion of possible measurements of P-violating
geometric phases in lABSE experiments. 相似文献
2.
We present a study of parity (P) violating contributions to the eigenenergies of stationary systems containing atoms in spatially inhomogeneous external electric fields. In this context the subtle interplay of P-violation and time reversal (T) invariance plays an important role. If the entire field configuration is chosen to exhibit chirality the energies are in general shifted by pseudoscalar contributions which change sign under a planar reflection of the field. In part I we consider sudden variations of the fields and calculate P-violating energy shifts using perturbation theory. In part II the adiabatic case will be treated and the connection to geometrical (Berry-) phases will be elucidated. To calculate the effects we use the standard model of elementary particle physics where the P-odd interaction arises through the exchange of Z-bosons between the quarks in the nucleus and the atomic electrons. We consider in detail hydrogen-like systems in unstable levels of principal quantum number n = 2. We study atoms with vanishing nuclear spin like
and with nuclear spin I = 1/2 like
. The nominal order of P-violating effects is 10−5...10−9 Hz which is determined by the mixing of the 2S1/2 and 2P1/2 states. However we point out that with certain configurations of the external fields, it is possible to enhance the P-violating energy shifts dramatically! Instead of energy shifts linear in the P-violation parameters we get then shifts proportional to the square root of these parameters. Numerically we find such energy shifts which only appear for unstable states to be of order 10−5...1 Hz. Under a reversal of the handedness of the external field configuration these P-violating shifts get multiplied by a phase factor i, i.e. the shifts in the real and imaginary part of the complex eigenenergies are exchanged. Application of our technique to hydrogen-like atoms with a nucleus of spin I = 1/2 yields P-violating energy shifts which are very sensitive to the nuclear spin dependent P-odd force, which receives a rather large contribution from the polarized strange quark density in polarized nuclei. Thus, a measurement of these energy shifts could provide an important tool to elucidate nuclear properties connected to the so called “spin crisis”. We also present a method for treating degenerate perturbation theory which combines advantages of both, Kato’s and Bloch’s methods.Work supported by Deutsche Forschungsgemeinschaft, Project No. Na 296/1-1Supported by Cusanuswerk 相似文献
3.
T. Gasenzer O. Nachtmann M. -I. Trappe 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2012,66(5):1-23
We discuss the geometric phases and flux densities for the metastable states of hydrogen with principal quantum number n = 2 being subjected to adiabatically varying external electric and magnetic fields. Convenient representations of the flux densities as complex integrals are derived. Both, parity conserving (PC) and parity violating (PV) flux densities and phases are identified. General expressions for the flux densities following from rotational invariance are derived. Specific cases of external fields are discussed. In a pure magnetic field the phases are given by the geometry of the path in magnetic field space. But for electric fields in presence of a constant magnetic field and for electric plus magnetic fields the geometric phases carry information on the atomic parameters, in particular, on the PV atomic interaction. We show that for our metastable states also the decay rates can be influenced by the geometric phases and we give a concrete example for this effect. Finally we emphasise that the general relations derived here for geometric phases and flux densities are also valid for other atomic systems having stable or metastable states, for instance, for He with n = 2. Thus, a measurement of geometric phases may give important experimental information on the mass matrix and the electric and magnetic dipole matrices for such systems. This could be used as a check of corresponding theoretical calculations of wave functions and matrix elements. 相似文献
4.
T. Bergmann T. Gasenzer O. Nachtmann 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(2):211-227
We discuss and calculate parity conserving (PC) and parity violating (PV) geometric phases for the metastable 2S states of
hydrogen and deuterium. The atoms are supposed to be subjected to slowly varying electric and magnetic fields which act as
external parameters for the atoms. Geometric flux density fields are introduced which allow for an easy overview how to choose
the paths in parameter space in order to obtain only PC or only PV geometric phases. The PV phases are calculated in the Standard
Model of particle physics. Even if numerically they come out small they have interest of principle as a new manifestation
of parity violation in atomic physics.
Electronic supplementary material Supplementary Online Material 相似文献
5.
M.C. Marques J.F.F. Mendes 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(1):123-127
We propose and study a model where two aspects are present: parity conservation and infinitely many absorbing states. Whereas
steady-state simulations show that the static critical behaviour is not affected by the presence of multiple absorbing configurations,
the influence of the initial state associated with the presence of slowly decaying memory effects is clearly displayed in
time dependent simulations. We report results of a detailed investigation of the dependence of critical spreading exponents
on the initial particle density.
Received 13 January 1999 and Received in final form 7 April 1999 相似文献
6.
V.G. Molinari M. Sumini F. Rocchi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(2):211-217
The study of quantum degenerate gases has received much interest in these last years essentially thanks to the extremely important
experimental results of the achievement of Bose-Einstein condensation of atoms and, very recently, of almost complete degeneracy
of atomic fermion gases. Here we want to present the results of a semi-analytical method for the study of an interacting degenerate
fermion gas based on semiclassical kinetic theory; special care has been devoted to the study of a rotating electron gas,
in a cylindrically symmetrical configuration, radially confined by a uniform magnetic field. The model will lead to a particular
Thomas-Fermi equation which is generalized to take into account finite temperature and average velocity of the gas, and which
is further developed to consider the effects of external fields.
Received 10 March 2000 相似文献
7.
C. A. Duque M. E. Mora-Ramos E. Kasapoglu H. Sari I. Sökmen 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,81(4):441-449
In this work are studied the intense laser effects on the impurity states in GaAs-Ga1−
x
Al
x
As quantum wells under applied electric and magnetic fields. The electric field is taken oriented along the growth direction
of the quantum well whereas the magnetic field is considered to be in-plane. The calculations are made within the effective
mass and parabolic band approximations. The intense laser effects have been included through the Floquet method by modifying
the confinement potential associated to the heterostructure. The results are presented for several configurations of the dimensions
of the quantum well, the position of the impurity atom, the applied electric and magnetic fields, and the incident intense
laser radiation. The results suggest that for fixed geometry setups in the system, the binding energy is a decreasing function
of the electric field intensity while a dual monotonic behavior is detected when it varies with the magnitude of an applied
magnetic field, according to the intensity of the laser field radiation. 相似文献
8.
L.D. Barron 《Molecular physics》2013,111(6):1395-1406
The rôle of time reversal symmetry in natural and magnetic optical activity is discussed. Natural optical rotation is shown to be generated by an anti-hermitian odd parity time-even operator and magnetic optical rotation by an anti-hermitian even parity time-odd operator. This shows that lack of time reversal invariance is not the source of natural optical rotation and that free atoms can show natural optical rotation without violating reversality, which leads to a fundamental distinction between the conditions necessary for natural optical rotation and a permanent space-fixed electric dipole moment. General transition optical activity and polarizability tensors between components of degenerate states are discussed with reference to possible new Raman experiments and new contributions to discriminating intermolecular forces between chiral molecules. Time reversal symmetry also leads to a new criterion for chiral objects and to the concept that natural optical activity provides an example of spontaneous symmetry breaking with respect to CP. 相似文献
9.
Reflection of cold atoms from an array of current-carrying wires 总被引:1,自引:0,他引:1
D.C. Lau A.I. Sidorov G.I. Opat R.J. McLean W.J. Rowlands P. Hannaford 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,5(2):193-199
We report the realization of a new type of magnetostatic mirror for slowly moving atoms which comprises a planar array of
parallel wires alternately carrying electric current in opposite directions. One of the features of this atomic mirror is
that the magnetic field may be readily varied, switched or modulated by altering the current in the wires. Reflection signals
close to 100% at a pulsed current of 3 A are demonstrated for a beam of free-falling laser-cooled cesium atoms at normal incidence.
The current dependence of the reflection signals exhibits structure which is associated with the sequential onset of reflection
of cesium 62
S
1/2
, F=4 atoms in the m=+4, +3, +2 and +1 magnetic states. Measurements of the spatial distribution of the reflected atoms indicate the reflection
is predominantly specular at currents of 3 A.
Received: 31 August 1998 / Accepted: 6 October 1998 相似文献
10.
A.V. Shtoff M. Rérat S.I. Gusarov 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,15(2):199-208
Floquet theory is used to describe the response of a molecule to applied radiation electric field. The method of ab initio calculation of frequency dependent (hyper)polarizabilities based on combination of perturbation theory with the finite field
method has been developed. Electron correlation is taken into account by means of the CIPSI algorithm. The total wave function
expansion involves spectral, pseudo-spectral states and polynomial terms. The developed approach is applied to the calculation
of the second hyperpolarizability of the lithium hydride molecule subjected to the superposition of harmonic and static electric
fields. The method can be used to calculate the higher order nonlinear properties of molecules.
Received 23 November 2000 and Received in final form 25 March 2001 相似文献
11.
Longitudinal atomic beam spin echo experiments: a possible way to study parity violation in hydrogen
Maarten DeKieviet Thomas Gasenzer Otto Nachtmann Martin-I. Trappe 《Hyperfine Interactions》2011,200(1-3):35-40
We discuss the propagation of hydrogen atoms in static electric and magnetic fields in a longitudinal atomic beam spin echo (lABSE) apparatus. Depending on the choice of the external fields the atoms may acquire both dynamical and geometrical quantum mechanical phases. As an example of the former, we show first in-beam spin rotation measurements on atomic hydrogen, which are in excellent agreement with theory. Additional calculations of the behaviour of the metastable 2S states of hydrogen reveal that the geometrical phases may exhibit the signature of parity-(P-)violation. This invites for possible future lABSE experiments, focusing on P-violating geometrical phases in the lightest of all atoms. 相似文献
12.
B. Pinto Da Souza R. Battesti C. Robilliard C. Rizzo 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,40(3):445-452
We study linear and bilinear magneto-electro-optical effects due to the propagation of light in centro-symmetric media in
the presence of P, T violating interactions and external
transverse and longitudinal electric and/or magnetic fields. We show that new magneto-electric optical effects appear. In
particular, we show the existence of a Jones birefringence
proportional to the square of the transverse field amplitude. All these effects are an unambiguous signature of the P, T violation,
and a search for such new phenomena could also provide novel
limits on electric dipole moment (EDM) of matter. 相似文献
13.
Bersuker IB 《Physical review letters》2012,108(13):137202
The conditions of multiferroicity in d(n) perovskites are derived from the pseudo Jahn-Teller effect, due to which ferroelectric displacements are triggered by vibronic coupling between ground and excited electronic states of opposite parity but same spin multiplicity; it takes place for some specific d(n) configurations and spin states only. In combination with the high-spin-low-spin crossover effect this leads to a novel phenomenon, the magnetic-ferroelectric (multiferroics) crossover which predicts magnetoelectric effects with exciting functionalities including electric magnetization and demagnetization. 相似文献
14.
T. Cheng J. Liu S. Chen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(1):19-26
In this paper, we investigate the dynamics of a hydrogen atom in high-frequency (several atomic units) super strong (up to
several tens of atomic units) laser fields within the high frequency Floquet theory framework. The ionization rate, ionization
spectrum, angular distribution and high-order harmonic generation are all investigated. Our studies reveal the universal behavior
of the total ionization rate, excess-photon ionization spectrum and angular distribution of the ionization rate in the stabilization
regime, and achieve a deep insight into the dynamics of high-order harmonic generation in the stabilization regime.
Received 6 June 2001 and Received in final form 31 August 2001 相似文献
15.
M.E. Mora-Ramos C.A. Duque E. Kasapoglu H. Sari I. Sökmen 《Journal of luminescence》2012,132(4):901-913
In this work we are studying the intense laser effects on the electron-related linear and nonlinear optical properties in GaAs–Ga1?xAlxAs quantum wells under applied electric and magnetic fields. The calculated quantities include linear optical absorption coefficient and relative change of the refractive index, as well as their corresponding third-order nonlinear corrections. The nonlinear optical rectification and the second and third harmonic generation coefficients are also reported. The DC applied electric field is oriented along the hererostructure growth direction whereas the magnetic field is taken in-plane. The calculations make use of the density matrix formalism to express the different orders of the dielectric susceptibility. Additionally, the model includes the effective mass and parabolic band approximations. The intense laser effects upon the system enter through the Floquet method that modifies the confinement potential associated to the heterostructure. The results correspond to several configurations of the dimensions of the quantum well, the applied electric and magnetic fields, and the incident intense laser radiation. They suggest that the nonlinear optical absorption and optical rectification are nonmonotone functions of the dimensions of the heterostructure and of the external perturbations considered in this work. 相似文献
16.
Feng Zhai Yong Guo Bing-Lin Gu 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(1):147-152
We adopt the group velocity approach to the issue of tunneling time in two configurations of magnetic barrier structures,
which are arranged with identical or unidentical building blocks. The effects of an external electric field are also taken
into account. The tunneling time in magnetic barrier structures is found to be strongly dependent on the magnetic configuration,
the applied bias, the incident energy as well as the longitudinal wave vector. The results indicate that for electrons with
equal energy but different incident angles, the tunneling processes are significantly separated in time within the same magnetic
barrier structure. In the configuration arranged with unidentical building blocks, there exists obvious asymmetry of tunneling
time in two opposite tunneling directions. Such a discrepancy of the tunneling time varies distinctly with the longitudinal
wave vector and the applied bias.
Received 4 March 2002 / Received in final form 22 May 2002 Published online 17 September 2002 相似文献
17.
In this work the effects of intense laser on the electron-related nonlinear optical absorption and nonlinear optical rectification in GaAs-Ga1−xAlxAs quantum wells are studied under, applied electric and magnetic field. The electric field is applied along the growth direction of the quantum well whereas the magnetic field has been considered to be in-plane. The calculations were performed within the density matrix formalism with the use of the effective mass and parabolic band approximations. The intense laser effects are included through the Floquet method, by modifying the confining potential associated to the heterostructure. Results are presented for the nonlinear optical absorption, the nonlinear optical rectification and the resonant peak of these two optical processes. Several configurations of the dimensions of the quantum well, the applied electric and magnetic fields, and the incident intense laser radiation have been considered. The outcome of the calculation suggests that the nonlinear optical absorption and optical rectification are non-monotonic functions of the dimensions of the heterostructure and of the external perturbations considered in this work. 相似文献
18.
H. Ring R.T. Carter J.R. Huber 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(1):73-81
We demonstrate the application of a pulsed magnetic field for the creation and manipulation of coherences in molecular systems,
using quantum beat spectroscopy for the detection of the dynamics of the molecular superposition states. In all cases, the
experiments are performed on energy levels in electronically excited states of the (jet-cooled) CS2 molecule populated by a short laser pulse. In the basic experiment, following excitation of initially degenerate Zeeman sublevels
under zero field conditions with suitable laser polarization, quantum beats are generated at the moment the magnetic field
is switched on, even when the field is delayed by several excited state lifetimes. By quenching of the field, it is shown
that the molecule may be “frozen” in any superposition state of the participating sublevels. Using a combination of static
and pulsed fields with different orientations, the molecule can be prepared in a more general state, described by coherences
among all Zeeman substrates. This is achieved by choosing an appropriate time delay for the switched field, without any change
to the geometrical parameters of the experiment such as laser polarization or detection direction. Numerical simulations of
these dynamical coherence phenomena have been performed to support assignment and interpretation of the experimental results.
Received: 8 April 1998 / Accepted: 3 June 1998 相似文献
19.
L.F. Rybaltchenko N.L. Bobrov V.V. Fisun I.K. Yanson A.G.M. Jansen P. Wyder 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(3):475-480
The influence of electric fields and currents has been investigated in the high- superconductors YBaCuO and BiSrCaCuO using a point-contact geometry with Ag as the counterelectrode, which reveal switching
transitions between states of a different resistance. The origin of this effect in point contacts is associated with electromigration
of the oxygen, driven by the electric field as well as by the current-induced “electron wind”. The switching effect preserves
its basic features at elevated temperatures up to room temperature and in high magnetic fields up to 10 T.
Received 23 November 1998 相似文献
20.
I.O. Kulik T. Hakioğlu A. Barone 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(2):219-226
We examine a generic three level mechanism of quantum computation in which all fundamental single and double qubit quantum
logic gates are operating under the effect of adiabatically controllable static (radiation free) bias couplings between the
states. Under the time evolution imposed by these bias couplings the quantum state cycles between the two degenerate levels
in the ground state and the quantum gates are realized by changing Hamiltonian at certain time intervals when the system collapses
to a two state subspace. We propose a physical implementation of the mechanism using Aharonov-Bohm persistent-current loops
in crossed electric and magnetic fields, with the output of the loop read out by using a quantum Hall effect aided mechanism.
Received 26 March 2002 / Received in final form 8 July 2002
Published online 19 November 2002 相似文献