Dynamic Jahn-Teller Interaction Research Articles

Theory of the optical spin-polarization loop of the nitrogen-vacancy center in diamond

The nitrogen-vacancy (NV) center in diamond is of high importance in quantum information processing applications which relies on the efficient optical polarization of its electron spin. However, the full optical spinpolarization process, in particular, the intersystem crossing between the shelving singlet state and the ground state triplet, is not understood. Here we develop a detailed theory on this process which involves strong electron-phonon couplings and correlation of electronic states that can be described as a combination of pseudo and dynamic Jahn-Teller interactions together with spin-orbit interaction. Our theory provides an explanation for the asymmetry between the observed emission and absorption spectra of the singlet states. We apply density functional theory to calculate the intersystem crossing rates and the optical spectra of the singlets and we obtain good agreement with the experimental data. As NV center serves as a template for other solid-state-defect quantum bit systems, our theory provides a toolkit to study them that might help optimize their quantum bit operation.

Singlet levels of the NV− centre in diamond

The characteristic transition of the centre at 637 nm is between and triplet states. There are also intermediate and singlet states, and the infrared transition at 1042 nm between these singlets is studied here using uniaxial stress. The stress shift and splitting parameters are determined, and the physical interaction giving rise to the parameters is considered within the accepted electronic model of the centre. It is established that this interaction for the infrared transition is due to a modification of electron–electron Coulomb repulsion interaction. This is in contrast to the visible 637 nm transition where shifts and splittings arise from modification to the one-electron Coulomb interaction. It is also established that a dynamic Jahn–Teller interaction is associated with the singlet state, which gives rise to a vibronic level 115 cm−1 above the electronic state. Arguments associated with this level are used to provide experimental confirmation that the is the upper singlet level and is the lower singlet level.

MODIFIED BCS GAP EQUATION FOR JAHN–TELLER DISTORTED HIGH TEMPERATURE SUPERCONDUCTORS

In this communication we report the interplay of the normal electron-phonon (EP) interaction, dynamic Jahn–Teller (DJT) distortion and superconductivity in high temperature superconductors in presence of a static lattice strain. This model consists of a degenerate two orbital band separated by Jahn–Teller (JT) energy modified by the DJT interaction in the conduction band. The superconductivity is assumed to be s-wave type present in the same band. The interaction Hamiltonian is solved by Green's function method and a modified BCS gap equation is obtained with a modified conduction band energy [Formula: see text] and modified BCS order parameter [Formula: see text] with α = 1, 2 designating the two orbitals. This interplay displays some new interesting results which are different from the effect of the static lattice strain on superconducting (SC) order parameter. The interplay is studied by varying the normal EP coupling, the DJT coupling, the SC coupling, the phonon vibration frequency, the phonon wave vector and other model parameters of the system.

Treatment of nonadiabatic interactions in polyatomic molecules by the frame transformation method: Application to the methyl iodide spectrum

The frame transformation for an s-wave electron in the field of a degenerate symmetric top molecular ion core is used to interpret the results of a series of rotational bandshape fittings of one- and two-photon absorption spectra of methyl iodide in the region of the lowest Rydberg transitions. The frame transformation is defined between alternative representations of the total wavefunction in which the spin of the Rydberg electron is successively decoupled from the molecular frame to the laboratory frame. It is shown that uncoupling of the spin from the molecular axis is essentially complete in the 6s states of CH3I. Calculations are also presented which indicate that the dynamic Jahn-Teller interaction leds to substantial angular momentum quenching in some vibronic levels of this molecule.

Fine structure of the (S1←S) band origins of phthalocyanine molecules in helium droplets

The laser-induced fluorescence (LIF) excitation spectra of free base phthalocyanine (Pc), Mg-Pc, and Zn-Pc molecules in superfluid helium droplets at T=0.38 K have been studied. The spectra reveal the rich vibronic structure of the S(1)<--S(0) electronic transitions. The band origins of the transitions consist of zero phonon lines accompanied by phonon wings, which originate from simultaneous electronic excitation of the molecule and excitation of the collective modes of the helium surrounding it. The phonon wings have discrete structures suggesting localization of some helium atoms in the neighborhood of the molecules. Zero phonon lines of Mg-Pc and Zn-Pc molecules are split into three components, which are separated by 0.2-0.4 cm(-1). Possible mechanism of splitting involves static or dynamic Jahn-Teller interaction of metal-phthalocyanine molecules in the twofold degenerate S(1)((1)E(u)) state with the helium shell.

Dynamic Jahn-Teller effect and superconductivity in MgB2

We propose a novel mechanism of superconductivity in MgB2 based on the dynamic Jahn-Teller interactions between the doubly degenerate pσ electronic states and the E2g phonon modes. The hopping motion of holes in the pσ states of the 2D B layers is constrained by accompanying phonons, and thereby a non-trivial superconducting state with multiple order parameters is found to arise from conventional electron–phonon interactions due to the presence of additional pairing channels.

Near and Far Infrared Transitions of Fe2+ in Cubic II–VI Semiconductors: Dynamic Jahn-Teller Interaction*

Near and Far Infrared Transitions of Fe²⁺ in Cubic II–VI Semiconductors: Dynamic Jahn-Teller Interaction*

Vibronic spectroscopy and dynamics in the jet-cooled silver trimer

Silver atom clusters are produced in a supersonic molecular beam with pulsed-nozzle laser vaporization. Mass-resolved two-photon photoionization produces an electronic spectrum for the trimer (Ag 3) with an origin at 27010±10 cm −1 (3.35 eV). Vibronic structure extending over 1500 cm −1 involves cleanly resolved bands at low energy merging to a quasi-continuum at higher energy. Vibronic analyses are considered for a triangular structure with or without Jahn-Teller distortion in the excited state. No simple analytic expression successfully fits the level structure. However, the spectrum is qualitatively consistent with dynamic Jahn-Teller interaction for a hindered pseudorotor with an excited state barrier of about 200 cm −. Vibrational frequencies are 161.1 cm −1 (stretch) and 96.3 cm −1 (bend).

ChemInform Abstract: The 5‐ and 6‐Coordinated Copper(2 +) Complexes with Terpyridine Ligands ‐ Cases v of Dynamic, Static and Cooperative Jahn‐Teller Interactions

Chemischer InformationsdienstVolume 17, Issue 38 Reviews ChemInform Abstract: The 5- and 6-Coordinated Copper(2 +) Complexes with Terpyridine Ligands - Cases v of Dynamic, Static and Cooperative Jahn-Teller Interactions D. REINEN, D. REINENSearch for more papers by this author D. REINEN, D. REINENSearch for more papers by this author First published: September 23, 1986 https://doi.org/10.1002/chin.198638360Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume17, Issue38September 23, 1986 RelatedInformation

The Deep Impurity Conduction Band Charge Transfer Transition In ZnSe:Co

Novel absorption and luminescence features observed in ZnSe:Co were described briefly in a recent paper. The associated transitions involve three high energy excited states, L, M and N, of Co|£. This is established from the appearance of these transitions in the excitation spectra of the4T2-&gt;4A2infrared luminescence of C o|£ and the observation of luminescence from the lowest excited state L to four different spin quartet states of Co2+whose energy separations are accurately known from infrared absorption. The present paper contains a m uch more complete account of the experiNovel absorption and luminescence features observed in ZnSe: Co were described briefly in a recent paper. The associated transitions involve three high energy excited states, L, M and N, of Co|£. This is established from the appearance of these transitions in the excitation spectra of the 4T 2 -&gt; 4A2 infrared luminescence of C o|£ and the observation of luminescence from the lowest excited state L to four different spin quartet states of Co2+ whose energy separations are accurately known from infrared absorption. The present paper contains a much more complete account of the experimental properties of these new transitions, including a detailed study of the magneto-optical properties and behaviour under uniaxial stress of transition L and its satellites. Among three possible models for the new states, two are discarded, particularly in view of the weak phonon coupling and the symmetric positive form of the L, M and N absorption lines. The remaining model is closely associated with the impurity -&gt; conduction band charge transfer process since the excited states are described w ith two weakly interacting parts, the Co3+im purity core and a relatively weakly bound electron in three different syfnmetric excited states. The symmetry and F-value of excited state L are readily described by a Hamiltonian containing spin—orbit and exchange in teraction terms. However, the properties of the lower satellite L ' (2.363 eV) indicate a vibronic character which requires a dynamic Jahn-Teller interaction term . The parameters of the model required by experiment appear reasonable.

Jahn–Teller interactions at Cr2+in GaAs

Abstract The theory for the splitting of the 5T2 and 5E states of Cr2+(3d4) ions on tetrahedral sites is formulated with inclusion of dynamic Jahn–Teller interactions. These modify the electronic features of the system through a quenching of certain operators. The splitting between lower lying levels of the 5T2 state, which is expressed by a zero-field spin Hamiltonian DSz 2 with S = 2, is consistent with three distinct interpretations. Inclusion of anharmonic vibronic coupling in the 5E state affects the upper levels of this state. The theoretical results derived are discussed with particular relevance to recent E.S.R. and photoluminescence results for Cr2+:GaAs.

Optical absorption and photoluminescence of vanadium in n-type GaAs

Optical spectra of V:GaAs are observed to have a well-defined characteristic structure, the absorption spectra around 1.2 eV being typical of an s → p type of electronic transition involving dynamic Jahn-Teller interactions. Photoluminescence at 0.8 eV shows a resolved phonon structure at low temperatures becoming Gaussian at high temperatures, the electron- phonon interaction being described by a Huang-Rhys factor S = 4.5 with coupling of modes of energy h ̵ ω = 9 meV . Using DLTS no level associated with Vanadium has been found which could be located further than 0.2 eV from the band edges leading us to conclude that V does not introduce electrically important levels in the gap. The absorption spectrum is associated with internal transitions at V 3+ on a gallium site. Although the origin of the photoluminescence is uncertain it could involve association of the vanadium with another lattice defect.

Mössbauer and far infrared evidence for a dominant Eg vibronic coupling in CaO:Fe 2+

The CaO:Fe 2+ system has been studied by Mössbauer spectroscopy in external magnetic fields and by far infrared spectroscopy. Using Ham's model, one can conclude that the CaO:Fe 2+ system exhibits a very strong dynamic Jahn-Teller interaction with a dominant coupling with the E g modes of vibration of the ligand complex.

Jahn-Teller instability and the magnetic circular dichroism of a tetragonal molecular system

The consequences for the absorption and magnetic circular dichroism (m.c.d.) spectra of Jahn-Teller coupling in an E orbital state of a molecule with C4v symmetry are investigated. The models used cover both static and dynamic Jahn-Teller interactions, the former allowing simple illustration of the interactions and their effects on the m.c.d. spectra. The moments of the spectra are discussed, as is the orbital reduction factor which is found to be oscillatory as a function of excitation energy in the presence of Jahn-Teller coupling.

Stress-Induced Dichroism and Energy Shifts in theA,B, andCAbsorption Bands in KCl: Tl

The effects of uniaxial stress on the $A$, $B$, and $C$ absorption bands of KCl: Tl are determined using a static and dynamic Jahn-Teller interaction. The uniaxial stress alters the local symmetry giving rise to preferred spacial directions which, in turn, causes dichroism in the observed absorption spectra. The dynamic interaction accounts for the time-average splitting of energy levels which manifests itself by causing shifts in the band peaks. A calculation of the polarization effects and the shifting of the energy levels is carried out for the cases of [001] and [110] uniaxial stress. This is accomplished by (a) determining the transition probabilities for transitions from the $6{s}^{2}$ ground state to the $6s6p$ excited state of ${\mathrm{Tl}}^{+}$ in both ${D}_{4h}(001)$ and ${D}_{2h}(110)$ environments and (b) determining the excited-state eigenenergies in terms of the interaction modes characterized by the above symmetries. The results are shown to compare favorably with recent available experimental results. Several theoretical conclusions are reached which await experimental verification.

The dynamic jahn-teller effect with many frequencies: a simple approach to a complicated problem

The hamiltonian for an ion which has a dynamic Jahn-Teller interaction with the many normal modes of a crystal can be separated in such a way that nearly all the coupling strength is concentrated in an interaction with a set of vibrations of one frequency only. All the rest of the hamiltonian, including the consequence of the effective vibration not being a normal mode, is expressed in a simple form, and treated as a second order perturbation on the energy levels of the first part. This procedure gives a good approximation to the lower states of the Jahn-Teller system, and can be used in studying phonon scattering. Some results are derived for the case of an E electronic doublet at a cubic crystal site.

Line Shape of C Bands in Alkali Halide Phosphors by the Method of Moments

We have derived the optical absorption line shape for C bands in alkali halide phosphors by the method of moments. The dynamic Jahn–Teller interaction is considered in the excited T1u electronic states. This interaction is taken to be linear in the lattice displacements. The obtained line shape exhibits asymmetric triplet structure even in the linear electron–lattice interaction. The use of the quasi-classical approach (i.e. the use of the adiabatic approximation and Franck–Condon principle) for electronic transition to orbitally degenerate states is discussed by comparing the line shapes obtained in this approach with those obtained by the method of moments.

Manifestations of the dynamic Jahn-Teller effect in trigonally distorted defect centres

General effects resulting from the dynamic Jahn-Teller interaction on the single cubic symmetry T 2 orbital state, which in C3v forms a basis for the A 1 + E symmetry representations, are investigated. As a result of the discussion of the types of centre in various host lattices which are likely to exhibit these effects, we are led to consider the centre responsible for the ‘self-activated emission’ in II–VI semiconductors. It is shown that a combination of theory with the experimental E.S.R. and optical polarization data strongly suggests that a dynamic Jahn-Teller interaction is occurring in these centres.

Correlation between infrared absorption and paramagnetic copper centres in zinc and cadmium sulphide

Microwave and optical Zeeman data on paramagnetic copper defects are reviewed and analysed in relation to the infrared centre which yields 1.3-2.2 mu m emission in zinc and cadmium sulphide. Certain difficulties associated with the interpretation in terms of a Cu2+ model are discussed. Configuration and a dynamic Jahn-Teller interaction are introduced in order to provide a theoretical framework to account for the data. Close quantitative agreement between theory and experiment is not possible and can only be approached by introducing a large dynamic Jahn-Teller coupling. An alternative interpretation in terms of a cation vacancy model shows some promise if appreciable configuration interaction is invoked.