Boris Tsukerblat

Ben-Gurion University of the Negev | bgu · Department of Chemistry

We discuss the problem of electron transfer (ET) in mixed valence (MV) molecules that is at the core of molecular Quantum Cellular Automata (QCA) functioning. Theoretical modelling of tetrameric bi-electronic MV molecular square (prototype of basic QCA cell) is reported. The model involves interelectronic Coulomb repulsion, vibronic coupling and ET...

Multimode vibronic model for the two-electron square-planar mixed valence cluster is developed and applied to semiclassical analysis of localization-delocalization phenomenon. The model involves interaction of the excess electrons both with “breathing” (Piepho-Krausz-Schatz- PKS-type) vibrations and with the intercenter vibrations modulating electr...

p>Strong Coulomb repulsion between the two charges in a square planar mixed-valence cell in quantum cellular automata (QCA) allows to encode the binary information in the two energetically beneficial diagonal distributions of the electronic density. In this article we pose a question: to what extent is this condition obligatory for the design of th...

In the context of a computationally guided approach to the controllable electron transfer in mixed-valence (MV) systems, in this article, we study the electron transfer (ET) in the series of oxidized norbornadiene C7H8 (I) and its polycyclic derivatives, C12H12 (II), C17H16, (III), C27H24 (IV), and C32H28 (V), with variable lengths of the bridge co...

The present article is a short overview of the theoretical modeling of spin transitions in polymetallic compounds. As distinguished from many insightful reviews on this topic, the present work is focused on the nature of cooperative interaction of the metal clusters in molecular crystals with emphasis at the physical role of molecular vibrations an...

In this article, we present a critical discussion of the parametric regimes required for reaching the functionality of the two-electron square-planar tetrameric mixed-valence (MV) complexes as molecular cells in quantum cellular automata (QCA). Previous studies on molecular QCA were restricted by the limit case of strong Coulomb interaction that wa...

We discuss the possibility of using mixed-valence (MV) dimers comprising paramagnetic metal ions as molecular cells for quantum cellular automata (QCA). Thus, we propose to combine the underlying idea behind the functionality of QCA of using the charge distributions to encode binary information with the additional functional options provided by the...

The effects of the vibronic coupling in quantum cellular automata (QCA) based on the square planar mixed valence (MV) molecular cells comprising four paramagnetic centers (spin cores) and two excess mobile electrons are analyzed in the important particular case when the Coulomb energy gap between the ground antipodal diagonal‐type two‐electron conf...

In this article, we apply the two-mode vibronic model to the study of the dimeric molecular mixed-valence cell for quantum cellular automata. As such, we consider a multielectron mixed valence binuclear - type cluster, in which the double exchange, as well as the Heisenberg-Dirac-Van Vleck exchange interactions are operative, and also the local (“b...

In this review we summarize the results of recent studies of the mechanisms of magnetoelectric effect in mixed-valence molecules. Consideration of fairly different systems and emerging situations is united by a common physical concept of spin-dependent electric polarizability in a wide class of such systems. In many-electron dimers, which are on th...

In this article, we propose to use multielectron square-planar mixed-valence (MV) molecules as molecular cells for quantum cellular automata (QCA) devices. As distinguished from previous proposals in this area, in multielectron cells, the electronic pair encoding binary information is shared among localized spins (“spin cores”). Hopefully, this wil...

Here we propose a two-mode vibronic model of a molecular cell for quantum cellular automata. The interconnection between the parametric approach and ab initio evaluations for the cation-radical of tetramethyleneethane molecule is established.

The effect of the double exchange in a square-planar mixed-valence dn+1−dn+1−dn−dn–type tetramers comprising two excess electrons delocalized over four spin cores is discussed. The detailed analysis of a relatively simple d2−d2−d1−d1–type tetramer shows that in system with the delocalized electronic pair the double exchange is able to produce antif...

In this communication we propose to considerably extend the class of systems suitable as cells for quantum cellular automata (QCA) by including magnetic quantum dots and molecular mixed valence dimers exhibiting double exchange. As distinguished from the previous works we propose to use not only charges as the information carriers but also spin deg...

The purpose of this article is to answer the question of how symmetry helps us to investigate and understand the properties of nanoscopic magnetic clusters with complex structures. The systems of choice will be the three types of polyoxometalates (POMs): (1) POMs containing localised spins; (2) reduced mixed-valence (MV) POMs; (3) partially delocal...

In this review we shortly summarize in an accessible way the physical and nanoscale material science aspects of the promising field of molecular quantum cellular automata (QCA). QCA is a revolutionary paradigm in quantum electronics with promising application in the conceptually new computing scheme which can be referred to as “computing with molec...

Quantum dot cellular automata is a computing paradigm based on transistor-free logic, which in turn relies on the idea to encode binary information in the bistable charge configurations of quantum dots and process information via Coulomb interaction. In context of molecular implementation of quantum dot cellular automata, we have compared the proper...

In the context of the decisive role that vibronic interaction plays in functioning of molecular quantum cellular automata, in this article we give a comparative analysis of the two alternative vibronic approaches to the evaluation of the key functional characteristics of the molecular cells. The semiclassical Born-Oppenheimer approximation and the...

A new vibronic mechanism of stabilization of pair-delocalized electronic state in trigonal trimeric mixed valence complexes (such as iron-sulfur [Fe3S4]0 proteins) is proposed. As distinguished from the previously reported mechanism based on the Piepho-Krausz-Schatz model dealing with the local “breathing” vibrations, the present mechanism involves...

This paper belongs to the area of electrical manipulation of spins in quantum dots and molecular spins for quantum technologies. We propose a theoretical analysis of the electric field controllable superexchange in the two-electron linear arrays of quantum dots (“physical” molecules) and linear mixed-valence molecules based on metal ions in differe...

In this article we propose a vibronic pseudo Jahn-Teller model for partially delocalized mixed valence molecules aimed to the description of the magnetic coupling between the localized spins mediated by the delocalized electron. The simplest partially delocalized system which retain the main studied features is assumed to consist of an one-electron...

The article is devoted to the theoretical study of the four-site cells as the basic units in the architecture of quantum-dot or molecular cellular automata. The functional characteristics of two possible compositions of square cells for quantum cellular automata are compared. We analyze the properties of the tetrameric cells composed of two isolate...

In context of our studies of the electric field control over stimuli-responsive molecular materials in this article we report a detailed theoretical analysis of the electric field control of the spin-states, magnetic properties and charge distributions in the trigonal trimeric systems comprising a pair of mobile electrons or holes. Such systems are...

In this article the vibronic model for electric field switchable mixed-valence trimer containing two delocalized electrons or holes is proposed and examined. The role of the vibronic coupling on the electric field effects is analyzed by means of the semiclassical adiabatic approach and, alternatively, with the aid of of the numerical analysis of th...

We present a FORTRAN code based on a new powerful and efficient computational approach to solve multidimensional dynamic Jahn-Teller and pseudo Jahn-Teller problems. This symmetry-assisted approach constituting a theoretical core of the program is based on the full exploration of the point symmetry of the electronic and vibrational states. We also...

In this article we give a short overview of the theoretical background and properties of the unique polyoxovanadate K6[VIV15As6O42(H2O)]·8H2O (abbreviated V15) containing a cluster of the fifteen VIV ions and exhibiting layers of different magnetizations. Analysis of the magnetic and spectroscopic properties of this fascinating system constitutes a...

In this article we develop a vibronic model for the electric field control of antiferromagnetic superexchange in mixed valence (MV) triferrocenium complex FeIII-FeII-FeIII proposed as possible candidate for the molecular implementation of quantum logic gate. Along with the electronic interactions such as electron transfer between the iron ions in d...

In this article we propose molecular implementation of the quantum logic gate originally realized by the linear triple-quantum dot array accommodating two electrons. To reach this goal we propose to employ the mixed-valence triferrocenium complex exhibiting three isomeric forms with different oxidation degrees FeIII-FeII-FeIII , FeIII-FeIII-FeII ,...

In this paper we propose a toy model to describe the magnetic coupling between the localized spins mediated by the itinerant electron in partially delocalized mixed-valence (MV) systems. This minimal model takes into account the key interactions that are common for all of such kind systems, namely, electron transfer in the valence-delocalized moiet...

We show that an external homogeneous electric field can be used as a tool to create a controllable quantum entanglement between the two weakly coupled electronic spins of the mixed valence polyoxoanion [GeV14O40]⁸⁻. Within a simplified two-level picture of the electronic pair based on ab initio analysis of the parameters, we evaluate the temperatur...

The article summarizes the main results of application of the theory of the Jahn-Teller (JT) and pseudo JT effects to the description of molecular quantum dot cellular automata (QCA), a new paradigm of quantum computing. The following issues are discussed: 1) QCA as a new paradigm of quantum computing, principles and advantages; 2) molecular implem...

A stoichiometric SrAl2O4:Eu²⁺nanosized powder was synthesized by combustion method using urea at 500°C and calcinated at 1000ºC. The measurements of the luminescent properties of SrAl2O4:Eu²⁺ were carried out; additionally, theoretical study of the crystal field splitting of the Eu²⁺ 5d levels at two crystallographically different Sr positions in t...

In this article we focus on the electron-vibrational problem of the tetrameric mixed-valence (MV) complexes proposed for implementation as four-dot molecular quantum cellular automata (mQCA).1 Although the adiabatic approximation explored in Ref.2 is an appropriate tool for the qualitative analysis of the basic characteristics of mQCA, like vibroni...

In this article we focus on the study of spin-effects in a single square-planar mixed-valence cell comprising two electrons and in coupled molecular cells for quantum cellular automata. Using the vibronic model we demonstrate that the polarizabilities of the cell are different in spin-singlet and spin-triplet states of the electronic pair. Based on...

A new microscopic approach to the problem of cooperative spin crossover in molecular crystals containing binuclear complexes as structural units has been developed. The cooperative interaction arising from the coupling of the molecular mode to the acoustic phonons represents the cornerstone of the approach. Another important ingredient of the model...

Our interest in this article is prompted by the vibronic problem of charge polarized states in the four-dot molecular quantum cellular automata (mQCA), a paradigm for nanoelectronics, in which binary information is encoded in charge configuration of the mQCA cell. Here, we report the evaluation of the electronic levels and adiabatic potentials of m...

In this article, we present a new microscopic theoretical approach to the description of spin crossover in molecular crystals. The spin crossover crystals under consideration are composed of molecular fragments formed by the spin-crossover metal ion and its nearest ligand surrounding and exhibiting well defined localized (molecular) vibrations. As...

We demonstrate that the borderline class II/III magnetic mixed valence (MV) dimers which can be referred to as single molecule multiferroics provide a unique possibility to achieve electric field control of the electron transfer (ET) dynamics. As an example we consider a MV dimer d2-d1 in which extra electron is delocalized over two spin-cores ( s0...

Our interest in this article is prompted by the problem of the vibronic self-trapping of charge polarized states in the four-dot molecular quantum cellular automata (mQCA), a paradigm for nanoelectronics, in which binary information is encoded in charge configuration of the mQCA cell. We report the evaluation of the electronic states and the adiaba...

We propose the use of an electric field stimulus to strongly affect the optical properties of ferromagnetic mixed-valence (MV) dimers. This proposal is based on the prediction of an anomalous Stark effect in the intervalence absorption bands of these multi-electron MV systems. As distinguished from the conventional Stark effect observed in one-elec...

The molecular compound K$_6$[V$^{IV}_{15}$As$^{III}_6$O$_{42}$(H$_2$O)] $\cdot$ 8H$_2$O, in short V$_{15}$, has shown important quantum effects such as coherent spin oscillations. The details of the spin quantum dynamics depend on the exact form of the spin Hamiltonian. In this study, we present a precise analysis of the intramolecular interactions...

Here we report the evaluation of the electronic and vibronic levels of mixed-valence tetra-ruthenium (2Ru(II) + 2Ru(III)) systems (assembled as two coupled Creutz-Taube complexes) for which possible molecular implementations of quantum-dot cellular automata was proposed. These complexes are representatives of Robin and Day classes I, II, and III an...

A stoichiometric micro-sized powder SrAl2O4:Eu2+ was synthesized by traditional solid state reaction at 1250 °C. Low-temperature spectroscopic measurements revealed two luminescence bands at 450 nm and 512 nm; their origin was discussed. Theoretical calculations of the structural and optical properties of SrAl2O4:Eu2+ in the framework of the densit...

We propose a microscopic analytical approach to the description of the low-temperature dissipative intracluster electron transfer dynamics in centrosymmetric one-electron mixed-valence (MV) dimers. The dissipative system (bath) is supposed to consist of the acoustic phonons of the crystal surrounding that are coupled to the delocalized electron(s)...

Here we discuss the electronic and vibronic problems of mixed valency (MV) in molecular clusters which are of current interest in areas as diverse as solid-state chemistry, biochemistry, and molecular magnetism. Modern research in these areas is focused on the nanosized clusters at the border between classical and quantum scales and for this reason...

The results of first-principles calculations of the electronic structure of a spin-frustrated V15 cluster with the use of a generalized density functional scheme that allows non-collinear spin configurations are presented. By using the results of these calculations, it was possible to determine a Heisenberg– Dirac–Van Vleck (HDVV) Hamiltonian with...

In this article, we present a symmetry‐adapted approach aimed to the accurate solution of the dynamic vibronic problem in large scale Jahn‐Teller (JT) systems. The algorithm for the solution of the eigen‐problem takes full advantage of the point symmetry arguments. The system under consideration is supposed to consist of a set of electronic levels...

Multiferroic molecules for spintronics: In a many-electron mixed-valence dimer with dominant double exchange, as compared with antiferromagnetic superexchange, the electric field is shown to induce a spin crossover from the ferromagnetic spin state to the antiferromagnetic one. This leads to a sharp decrease in the magnetic moment of the molecule a...

Rabi oscillations in the V_15 Single Molecule Magnet (SMM) embedded in the surfactant DODA have been studied at different microwave powers. An intense damping peak is observed when the Rabi frequency Omega_R falls in the vicinity of the Larmor frequency of protons w_N , while the damping time t_R of oscillations reaches values 10 times shorter than...

We show here that mixed-valence (MV) magnetic molecules with a significant electron delocalization are extremely sensitive to an external electric field. In particular, we focus on the symmetric many-electron MV binuclear complexes that are on the borderline between Robin and Day classes II and III. In these molecules, the double-exchange, which ha...

In this contribution, we predict and theoretically investigate the effects of the electric field pulse in mixed valence (MV) dimers. These systems exhibit bistability with a large internal dipole moment mediated by the itinerant electron trapped by the vibronic coupling. In this sense, they are similar to single molecular magnets (SMMs) that are bi...

A stoichiometric SrAl2O4:Eu2 nanosized powder was synthesized by a combustion method using urea at 500°C and calcination at 1000ºC. The luminescence properties were investigated and two luminescence bands at 450 nm and 512 nm were observed at lower temperatures. This luminescence in the green region corresponds to transitions of Eu2 from 4f65d1 → 4...

We theoretically investigate the effects of a magnetic pulse on a single-molecule magnet (SMM) initially magnetized by a dc field along the easy axis of magnetization. In the Landau–Zener (LZ) scheme, it is shown that the final spin state is a function of the shape and duration of the pulse, conditioned by the decoherence time of the SMM. In the ca...

In this article we propose a model of spin-phonon relaxation in K6[VIV 15As6O42(H2O)]-8H2O, the so called V15 cluster exhibiting the unique layered magnetic structure. The work is motivated by the recent observation of the Rabi oscillation [1] in this system and aimed to elucidate the role of spin-phonon interaction as a source of decoherence. The...

In this paper we present a microscopic model for the cooperative spin-crossover (SCO) phenomenon in crystals containing cyano-bridged pentanuclear clusters {[MIII(CN)6]2[M′ II(tmphen)2]3} (M/M′ = Co/Fe, 1; Fe/Fe, 2) with a trigonal bipyramidal (TBP) structure. The low-spin to high-spin (ls–hs) transition is considered as a cooperative phenomenon th...

In this article we present a theoretical microscopic approach to the problem of cooperative spin crossover in crystals based on cyano-bridged pentanuclear metal clusters \(\{{[{\mathrm{M(CN)}}_{6}]}_{2}{[{\mathrm{Fe(tmphen)}}_{2}]}_{3}\}\) (M = Co, Os) with a trigonal bipyramidal structure. The low-spin to high-spin transition is considered as a co...

In this contribution we introduce the concept of single molecule ferroelectric based on the vibronic pseudo Jahn-Teller model of mixed valence dimeric clusters belonging to the Robin and Day class II compounds. We elucidate the main factors controlling the nonadiabatic Landau-Zener tunneling between the low lying vibronic levels induced by a pulse...

In this article we present a symmetry-adapted approach aimed to the accurate solution of the dynamic Jahn-Teller (JT) problem. The algorithm for the solution of the eigen-problem takes full advantage of the point symmetry arguments. The system under consideration is supposed to consist of a set of electronic levels \({\Gamma }_{1},{\Gamma }_{2}\ldo...

In this critical review we review the problem of exchange interactions in polynuclear metal complexes involving orbitally degenerate metal ions. The key feature of these systems is that, in general, they carry an unquenched orbital angular momentum that manifests itself in all their magnetic properties. Thus, interest in degenerate systems involves...

In this article we propose a model of spin-vibronic relaxation in K6[VIV15As6O42(H2O)]·8H2O, the so called V15 cluster exhibiting the unique layered structure. The work is motivated by the recent observation of the Rabi oscillation [1] in this system and aimed to elucidate the nature of the relaxation processes. The model assumes that the spin-phon...

This review article is a first attempt to give a systematic and comprehensive description (in the framework of the unified theoretical approach) of the exchange interactions in polynuclear systems based on orbitally degenerate metal ions in the context of their relevance to the modern molecular magnetism. Interest in these systems is related to the...

The term `molecular magnet' generally refers to a molecular entity containing several magnetic ions whose coupled spins generate a collective spin, S (ref. 1). Such complex multi-spin systems provide attractive targets for the study of quantum effects at the mesoscopic scale. In these molecules, the large energy barriers between collective spin sta...

The structural versatility characterizing polyoxometalate chemistry, in combination with the option to deliberately use well-defined building blocks, serves as the foundation for the generation of a large family of magnetic clusters, frequently comprising highly symmetric spin arrays. If the spin centers are coupled by antiferromagnetic exchange, s...

We present a FORTRAN code based on a new powerful and efficient computational approach to solve the double exchange problem for high-nuclearity MV clusters containing arbitrary number of localized spins and itinerant electrons. We also report some examples in order to show the possibilities of the program.

In this article we review applications of the concepts of the Jahn–Teller effect in molecular magnetism. The scope of the contemporary field of molecular magnetism and its fascinating applications are shortly described. The theoretical background of molecular magnetism as well as the applications of molecular magnets are closely related to the basi...

This article is a part of our efforts to control the magnetic anisotropy in cyanide-based exchange-coupled systems with the eventual goal to obtain single-molecule magnets with higher blocking temperatures. We give the theoretical interpretation of the magnetic properties of the new pentanuclear complex {[Ni(II)(tmphen)(2)](3)[Os(III)(CN)(6)](2)} x...

To develop a highly energy-efficient white light sources, one needs to design highly efficient yellow, green and red phosphors, which are able to absorb excitation energy of blue LEDs and generate emissions. In this paper, results on production of a new green multiphase thiogallate phosphor {SrGa 2S4 + MgGa2O4}: Eu2+ with improved luminescence prop...

A general approach to the problem of electron delocalization in the high-nuclearity mixed-valence (MV) clusters containing an arbitrary number of localized spins and itinerant electrons is developed. Along with the double exchange, we consider the isotropic magnetic exchange between the localized electrons as well as the Coulomb intercenter repulsi...

The terbium-activated yttrium tantalite (YTaO(4):Tb(3+)) phosphor is of great interest due to the interesting spectroscopic properties of rare earth ions in crystals and also practical use in x-ray imaging. Using the group-theoretical approach, we analyze the selection rules for the transition between Stark components of Tb(3+) in symmetry of the a...

We model the magnetic behavior of spin frustrated trinuclear clusters in the region of field induced crossover of the levels. The emphasis is made on a competitive role of the antisymmetric (AS) exchange and static structural distortions as well as on the consequences of the dynamic pseudo-Jahn–Teller (JT) instability. We employ the three-spin mode...

In this article we report for the first time experimental details concerning the synthesis and full characterization (including the single-crystal X-ray structure) of the spin-canted zigzag-chain compound [Co(H2L)(H2O)]infinity [L = 4-Me-C6H4-CH2N(CPO3H2)2], which contains antiferromagnetically coupled, highly magnetically anisotropic Co(II) ions w...

We propose a theoretical study of the magnetic behavior of spin frustrated trinuclear clusters in the region of the field induced crossover of the levels which are crucial for the description of the static magnetization and dynamic behavior in a sweeping field. The emphasis is made on a competitive role of the antisymmetric (AS) exchange and static...

This article is devoted to the problem of the electron–vibrational interaction in 4f–5d optical transitions and the calculation of the Stokes shift in thiogallate materials. Usually 4f–5d transitions give rise to the broad vibronic bands whose shape-function have been described and found, including terms corresponding to the emission (absorption) f...

We show that in molecular Ni4 clusters with S4 symmetry, not only the local anisotropy but also the antisymmetric exchange interaction contributes to the observed fourth-order anisotropy terms in the single-spin Hamiltonian. From a group-theoretical classification of the exchange-coupled multiplets, the effective spin Hamiltonian terms are determin...

This study is devoted to the problem of the electron–vibrational interaction in 4f–5d optical transitions. We analyze the room temperature experimental data on the vibronically assisted broad bands arising from the 4f–5d transitions in Ba, Ca, and Sr thiogallates doped with Eu2+ ions. An approximate simple expression is given for the shape function...

Rare-earth-doped oxynitride or nitride compounds have been reported to be photoluminescent and may then serve as new phosphors with good thermal and chemical stabilities. In this work, Ca-alpha-SiAlON:Eu2+ based yellow and orange oxynitride phosphors with compositions of Ca0.485Eu0.015Si9.2Al2.8O1.8N14.2 and Ca0.94Eu0.06Si9Al3ON15 were prepared usi...

In this paper we give a short overview of our efforts in the understanding of the magnetic properties of the fascinating nanoscopic cluster K6[VIV15As6O42(H2O)]·8H2O (hereafter V15) exhibiting layers of magnetization. We analyze EPR and adiabatic magnetization of the V15 cluster with a triangular VIV3 array causing spin frustration. A model for V15...

In this article we reconsider the discussion of the magnetic measurements for the two novel polyoxotungstates, (n-BuNH(3))(12)[(CuCl)(6)(AsW(9)O(33))(2)].6H(2)O and (n-BuNH(3))(12)[(MnCl)(6)(SbW(9)O(33))(2)].6H(2)O, which have been synthesized and characterized by Yamase et al. (Inorg.Chem. 2006, 45, 7698). Analysis of the magnetic susceptibility a...

In this article, we analyze the interplay between the antisymmetric (AS) exchange interaction and Jahn–Teller (JT) vibronic coupling in spin-frustrated systems with triangular units. AS exchange in these systems creates a strong first order magnetic anisotropy related to the orbitally degenerate frustrated ground state that is analyzed for the uniq...

In this article, we report the theoretical evaluation of the vibronic constants for the spinel-type crystals ZnAl2S4, ZnAl2Se4, CdAl2Se4, and CdIn2S4 doped with the transition metal ions Cr3+, Cr4+, Ti2+, and Ti3+. In these crystals the ions Cr3+, Ti3+ and Cr4+, Ti2+ occupy positions with octahedral and tetrahedral surrounding correspondingly. In t...