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CNAA / Theses / 2018 / July /

Study of metal-insulator transition in quasi-one-dimensional organic crystals


Author: Andronic Silvia
Degree:doctor of physics and mathematics
Speciality: 01.04.02 - Theoretical and mathematical physics
Year:2018
Scientific adviser: Anatolie Casian
doctor habilitat, professor
Institution: Moldova State University

Status

The thesis was presented on the 3 July, 2018
Approved by NCAA on the 23 November, 2018

Abstract

Adobe PDF document – 2.05 Mb / in romanian

Thesis

CZU 536.764 : 539.21

Adobe PDF document 5.11 Mb / in romanian
123 pages

Keywords

Peierls transition, quasi-one-dimensional organic crystals, tetrathiotetracene-iodide, tetrathiotetracene-tetracyanoquinodimethane, tetrathiofulvalinium-tetracyanoquinodimethane, molecular chains, Peierls critical temperature.

Summary

Research field: Peierls structural transition in quasi-one-dimensional organic crystals.

The main purpose consists in modeling of Peierls structural transitions in quasi-one-dimensional organic crystals of TTF-TCNQ, TTT(TCNQ)2 and TTT2I3 in order to determine some physical parameters from the comparison of the theoretical values of the Peierls critical temperature with the experimental ones.

The objectives: the application of a more complete physical model of quasi-one-dimensional organic crystals of the TTF-TCNQ, TTT(TCNQ)2 and TTT2I3 type to investigate the metalinsulator transition in these materials; numerical modeling of the renormalized phonon spectrum and polarization operator; determination of Peierls critical temperature.

Scientific novelty and originality: for the first time, a more complete physical model was applied to study the Peierls transition in quasi-one-dimensional organic crystals of TTF-TCNQ, TTT(TCNQ)2 and TTT2I3. Numerical modeling of the renormalized phonon spectrum is presented in the 2D and 3D approximation. For the first time, the Peierls transition was studied in the TTT(TCNQ)2 and TTT2I3 crystals.

The scientific problem solvedconsists in a more complete description of the metal-insulator transition of the Peierls type in the crystals of TTF-TCNQ, TTT(TCNQ)2 and TTT2I3; the numerical modeling of renormalized phonon spectrum and the determination of certain parameters for these materials.

Theoretical and practical importance: In the thesis it is presented a new, more complete study of the metal-insulator transition in Q1D organic crystals of TTF-TCNQ, TTT(TCNQ)2 and TTT2I3, and it is shown that the transition is of Peierls type. The renormalized phonon spectrum, that will be used later in the thermoelectric properties research, is modeled. The Peierls transition temperature is determined. The values of some parameters of the TTT(TCNQ)2 and TTT2I3 crystals are specified, which are implemented in the FP7 international project Nr. 308 768.