Welcome to the web page of the low temperature laboratory of the Universidad Autonoma de Madrid. Here you can find information about who we are and what we do. We belong to the Condensed Matter Physics Department and to the Institute Nicolás Cabrera of the Faculty of Sciences and the IFIMAC (Condensed Matter Physics Center) of the Universidad Autonoma de Madrid. We are associated to the Materials Science Institute of the Spanish Research Council, and are located in the UAM+CSIC Campus.
Enhancement of long-range correlations in a 2D vortex lattice by an incommensurate 1D disorder potential
Long range correlations in two-dimensional (2D) systems are significantly altered by disorder potentials. Theory has predicted the existence of disorder induced phenomena such as Anderson localization and the emergence of novel glass and insulating phases from the competition between interactions and disorder as for example the Bose glass. More recently, it has been shown that disorder breaking the 2D continuous symmetry, such as a one dimensional (1D) modulation, can enhance long range correlations. Experimentally, it remains difficult to and well-controlled model systems. Developments in quantum gases have allowed the study of the interplay between interaction and disorder and the observation of a wealth of phenomena including the transition between superfluid and insulating glassy states. However, there are no experiments exploring the effect of symmetry-breaking disorder. In 2D superconducting vortex lattices, vortex density and interactions can be varied in presence of quenched disorder by changing the magnetic field. Here, we create a 2D vortex lattice at 0.1 K in a superconducting amorphous thin film with a well-defined 1D thickness modulation and track the field induced modification in the vortex arrangements using scanning tunneling microscopy. We find that the 1D modulation becomes incommensurate to the vortex lattice and drives an order-disorder transition, behaving as a scale-invariant disorder potential. Through direct visualization of individual vortices, we show that the transition occurs in two steps and is mediated by the proliferation of topological defects. We calculate orientational and positional correlation functions and critical exponents. We find that they are far above theoretical expectations for scale-invariant disorder and that, unexpectedly, they follow instead the critical behaviour which describes dislocation unbinding melting. Our data show for the first time that randomness disorders a 2D crystal, and evidence the transformation induced by symmetry breaking disorder in interactions and the critical behaviour of the transition.
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Email to lbtuam (at) uam.es
Laboratorio de Bajas Temperaturas
Departamento de Física de la Materia Condensada
Modulo 03, 112, Facultad de Ciencias
c/ Francisco Tomás y Valiente, 7
Universidad Autónoma de Madrid
Tel: ++34 91 4974756