Electric transport and the pseudogap in the 1-2-3 HTSC system, under all-around compression (Review Article)

Abstract

The problem of how high pressure impacts various electric transport mechanisms in HTSC compounds REBa2Cu3O7-δ (RE = Y, or another rare-earth ion) is considered. The features of the crystal structure and the effects that structural defects of different morphologies have on the electrical conductivity of these compounds in the normal, pseudogap, and superconducting states, are discussed. A review of the experimental data obtained in studies on the effect of high hydrostatic pressure on the various electric transport mechanisms of REBa2Cu3O7-δ compounds, with varying composition and technical prehistory, is conducted. Different theoretical models devoted to the subject of how high pressure impacts the electrical conductivity of 1-2-3 HTSC system compounds are discussed.

Composition variation and electron irradiation effects on the fluctuation conductivity in Y1–zPrzBa2Cu3O7−δ single crystals

“…Synthesis of novel superconducting materials with improved current-carrying abilities via modification of their structure and characteristics of electronic transport is one of the active research directions of modern solid state physics [1][2][3][4]. For high-temperature superconducting cuprates, the most efficient experimental approaches to accomplish this task include the introduction of artificial pinning sites [5][6][7] as well as the modification of their electronic transport properties via exposure to ionizing radiation [8,9] and variation of the composition [10,11].…”

“…At the same time, the use of these approaches can noticeably affect the temperature dependence of the conductivity of these compounds, thereby creating conditions for the observation of a series of intriguing phenomena occurring in the non-superconducting state. Exemplary phenomena include the pseudogap anomaly [1,2,37], fluctuation paraconductivity [38,39], metal-insulator transitions [40,41], incoherent electronic transport [42,43], making these studies especially important from the viewpoint of basic research [1]. According to the contemporary understanding [44], it is these phenomena which may be key to the clearing of the microscopic nature of hightemperature superconductivity, which remains unexplained despite almost 35 years of intensive experimental and theoretical investigations.…”

“…In this work, we compare the effects of electron irradiation with the influence of Pr doping and oxygen deficiency on the fluctuation conductivity and characteristics of the superconducting state in YBa 2 Cu 3-O 7-d and Y 1-z Pr z Ba 2 Cu 3 O 7-d single crystals. It should be noted ahead that despite extensive experimental investigations [1,14], the mechanisms of the evolution of the different conductivity regimes in the course of irradiation of RBa 2 Cu 3 O 7-d compounds with electrons or variation of their elemental composition remain ultimately unclarified so far. One of the possible reasons for this can be the complexity of comparison of data for textured ceramic samples with a high content of intergranular bounds and films grown on different substrates by using different preparation techniques [14].…”

Transverse conductivity and the pseudogap in YBCO single crystals irradiated with fast electrons

“…Investigations of the pseudogap (PG) anomaly remain one of the most topical research lines in the physics of high-temperature superconductivity (HTS). [1][2][3] However, in spite of the overwhelming literature (reviews can be found, e.g. in Refs.…”

“…in Refs. [1][2][3][4][5], both the PG nature and its role in the formation of the superconducting state in HTSs remain unclear. In this regard, most promising are YBa 2 Cu 3 O 7−δ compounds 6,7 whose composition can be easily varied by substitution of Y for its isoelectronic analogues, 8,9 variation of the oxygen nonstoichiometry 10,11 or extreme exposures.…”