Is the Quantum Melting of a Polaron Wigner Crystal an Insulator-to-Superconductor transition ?

On examining the stability of a Wigner Crystal (WC) in an ionic dielectric, two competitive effects due to Polaron formation are found to be important: (i) the screening of the Coulomb forces which destabilizes the crystal, compensated by (ii) the increase of the carrier mass (polaron mass). The quantum melting of the Polaron Wigner Crystal (PWC) is examined. By calculating the quantum fluctuations of both the electrons and the polarization, we show that there is a competition between the dissociation of the Polarons at the insulator-to-metal transition (IMT), and a melting towards a polaron liquid. We find that at strong coupling ($\alpha > \alpha^*$), a liquid state of polarons cannot exist, and the IMT is driven by polaron dissociation. Next, we show that the dipolar interactions between localized polarons are responsible for a phonon instability of the PWC as the density increases. This provides a new mechanism for the IMT in doped dielectrics. Examining the sign of the dielectric constant of the PWC, we conjecture that such an instability could yield an Insulator-to-Superconductor transition.Comment: 4 Pages, 2 Figures included, Int. Conf. M2S-HTSC-VI (Houston 2000) to be published in Physica

On the stability of hole crystals in layered cuprates

Recent STM measurements have revealed the existence of periodic charge modulations at the surface of certain cuprate superconductors. Here we show that the observed patterns are compatible with the formation of a three-dimensional crystal of doped holes, with space correlations extending between different Cu-O layers. This puts severe constraints on the dynamical stability of the crystallised hole structure, resulting in a close relationship between the periodicity of the electronic modulation and the interlayer distance.Comment: completed reference list, fig. 3 corrected; accepted for publication in Eur. Phys. J. B, Rapid Note

Polaron structures in screening gas of light carriers

Subject of inquiry: electron processes in multilayer nanostructures. The aim of the work is to investigate stability of quasi-two-dimensional polaron structures depending upon the properties of light carriers screebing gas. The work covers theoretical substantiation of the existence of critical screening lenght such that polaron state destruction takes place. A phenomenon of Vigner's crystallization of polaron gas has been discussed. Parameters of screening system has beem determined under which polaron state of large radius exists. A spectrum of weak oscillations has been found for polaron grates in light carriers gas. The results may be used when determining kinetic and optical properties of stratified conducting materialsAvailable from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio