Local Polaronic Effects in Compounds with Atoms of Transition Metals
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The e-ph coupling may be of the different strength for different electronic bands. If coupling is strong enough for one or more bands, polaronic effects practically decouple these bands from the rest. Single ions being dressed by strong e-ph interactions move in the local potentials having two or more minima, and hence, can be viewed as the system of the Ising spins. Intersite interactions via the RKKY-type exchange by the electron-hole pairs tend to order the latter thus providing the CDW instability mechanism with a structural vector, Q that has nothing in common with the Fermi surfaces parameters. Among the most typical manifestations of such strong e-ph coupling in the system are large characteristic energy scales significantly exceeding the temperatures for the onset of the CDW phase. The available experimental data support interpretation of properties of the transition-atoms-dichalcogenides and the compounds of the A15 group in terms of the local polaronic effects.
KeywordsPolaronic effect Charge density waves Pairing
The paper is submitted for publication to the journal issue dedicated to Professor Jacques Friedel. The author is delighted by such opportunity to express his appreciation and his great personal respect to Jacques. Some 8 years’ difference in the age would usually mean in science the difference in one or two generations. I never perceived such difference in my contacts with Jacques. It is such pleasure to remember days when we both were so desperately interested in results of the search for superconductivity in organic metals at Orsay and to recollect the kind Jacques’ hospitality during my visits to France.
The work was supported by the NHMFL through NSF Grant No. DMR-0654118 and the State of Florida.