Photoinduced chain-oxygen ordering in detwinned YBa2Cu3O6.7 single crystals studied by reflectance-anisotropy spectroscopy

A. BRUCHHAUSEN; S. BAHRS; K. FLEISCHER; A. R. GOÑI; A. FAINSTEIN; G. NIEVA; A. A. ALIGIA; W. RICHTER; C. THOMSEN

PHYSICAL REVIEW B - CONDENSED MATTER AND MATERIALS PHYSICS

APS

Año: 2004 vol. 69 p. 224508 - 224508

0163-1829

We present a reflectance-anisotropy spectroscopy (RAS) investigation of photoexcitation and annealing effects in oxygen deficient detwinned YBa$_2$Cu$_3$O$_{6.7}$ single crystals. Well-resolved RAS spectral features are either bleached or enhanced on a time scale of hours upon laser illumination with polarization parallel to the Cu(1)-O(1) chains. These photoinduced effects recover with room temperature annealing in the dark. Based on previous ellipsometric studies and on cluster models for the oxygen Cu-O(1) chain-fragments we are able to assign the RAS peaks that depend on illumination to optical transitions involving copper atoms located either on short chain-fragments or in isolated Cu-O(4)$_{2}$ sites. This provides strong evidence that photoinduced chain-oxygen ordering is indeed at the origin of persistent photoconductivity and Raman vibrational mode bleaching in these materials.