Persistent photoconductivity inYBa2Cu3

В. И. Кудинов

¹

,

I. Chaplygin

²

,

Andrei Kirilyuk

³

et al.

Abstract

Persistent photoconductivity (P PC) and metastable photoinduced superconductivity, recently discovered in semiconducting YBa2Cu306+, have been investigated over the oxygen content of 0&x &1. Under exposure of semiconducting YBa,Cu306+ films (x =0.4) to visible light their resistance is found to decrease drastically. After interrupting the irradiation the resistance persists at this reduced level provided that the temperature is kept below 270 K. When the illumination dose is increased the semiconductorlike behavior of the films progressively changes to that of a metal and a superconductor. Prolonged irradiation leads to complete loss of resistivity below 5 K and simultaneous growth of a diamagnetic moment in the films, revealing pronounced enhancement of their superconducting properties. A slow relaxation of the PPC state was found only by warming the sample near to room temperature where it could be described by a thermally activated process with an energy barrier of -1 eV. The observed phenomena are attributed to photoexcitation of extra mobile holes into CuO, planes, allowing a metastable superconducting phase to be initiated. We also discuss feasible microscopic mechanisms of PPC in oxygen-deficient Y-Ba-Cu-0 films. It is suggested that the photoinduced superconductivity may have applications in fabrication of in situ optically tunable weak-link devices.

Electron–phonon Interactions Cause HTSC

“…This relaxation has been observed after two kinds of activation, with light (photo-induced (super)conductivity) 12 and high pressures 13 Table I.…”

Photon-induced switching and tunneling phenomena in a YBCO thin film junction

“…The photo-induced state was continuously initiated by a more than onehour illumination using the 1mW He-Ne laser with a cumulative photon dose about 10 22 photons/cm 2 , which is close to what was observed by V. I. Kudinov, etc. [5] During the illumination, the temperature of the YBCO junction was monitored by a thermocouple, and the maximum change in temperature was less than one and a half degrees (Celsius). The entire experiment was run at room temperature.…”

“…PPC and PISC of YBa 2 Cu 3 O 6+x thin films have received special attention [3][4][5][6][7][8][9], and the primary reason for this is because subsequent to visible illumination, the photo-induced state of YBa 2 Cu 3 O 6+x films has an increase in conductivity in the normal state (PPC) and an increase in the superconducting transition temperature Tc and diamagnetism in the superconducting state (PISC). It has been suggested that the PISC phenomena has several practical applications such as optically controlled superconductive switches [10].…”

X-ray-induced persistent photoconductivity in vanadium dioxide

“…To observe an increase in conductance, VO 2 would need to be reduced [33]. Since the beam is well localized, yet a large portion of the surface must participate to account for the photoconductance, a significant oxygen mobility would be required, which is only seen for layered or amorphous materials [34]. Therefore, if the observed PPC is associated with a structural transition, it must come in the form of a large number of narrow metallic filaments, since a single filament of the minimum required 85 nm width would still be detected.…”