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Contenu archivé le 2022-12-23

Interlayer tunnelling spectroscopy of condensed electronic states with charge, spin and magnetic ordering in layered nano-materials

Objectif

Strong electron correlation is a typical attribute of layered or chain conducting materials. Its major signature is a symmetry broken state, which acquires forms of several types of charge and spin orderings or superconductivity. Mechanisms of interlayer transport in these materials belong to fundamental issues of physics which are not yet resolved at either experimental or theoretical levels. Tunneling experiments provide a best tool for approaching these problems and for studying the nature of elementary excitations. A particular advantage comes from using local nanoscale probes applied to the unperturbed material. To study the interlayer tunneling we will use a variety of methods, especially the new techniques of intrinsic coherent tunneling. We will develop sub-micron sized stacked structures fabricated by means of focusing ion beams and artificial single junction structures. Additional manipulations by high magnetic fields (up to 30T) and temperature will permit to achieve an unprecedented accuracy in registration of spectral features. We plan to study several classes of substances like oxides and chalcogenides of transition metals, and organic compounds. Among them we will face materials with gapful ground states as well as with remnant carriers - corresponding to strongly correlated semiconductors and semimetals. We will deal with several types of electronic ground states, mostly from the general class of Electronic Crystals. There are charge density waves, phases with charge disproportionation (ordering) of ferroelectric and antiferroelectric types, antiferromagnetic states, superconductivity, Wigner crystals. Of particular interest are: spectroscopy of the energy gap/pseudogap; spectroscopy of the intragap localized states such as amplitude solitons; origin of the threshold voltage for interlayer tunneling in relation to collective modes; nature of the zero bias conductance peak observed for partly gapped cases; metal-insulator transition mediated by high magnetic field; spin polarized interlayer transport in layered magneto-oxides. The theoretical part of the project will support the understanding of the above experimental problems and will address general properties of states and dynamics of electrons in strongly correlated media with spontaneously broken symmetry. Particular attention will be given to the theory of interchain tunneling based on the concept of instantons, of effects of interchain or interplane correlations upon solitons. The project goals embrace a rich complex of solid state physics, largely at the leading edge of modern problematics and methodologies of nano-science: local properties of synthetic metals, semiconductors, insulators; nano-physics of strongly correlated low dimensional electronic systems; effects of high magnetic fields upon the electrons dynamics and the very ground state; theory of nonlinear dynamic processes related to various forms of solitons and collective effects.

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Coordinateur

UNIVERSITÉ JOSEPH FOURIER DE GRENOBLE
Contribution de l’UE
Aucune donnée
Adresse
AVENUE DES MARTYRS, 25
GRENOBLE
France

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Participants (4)