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Keywords:

  • fluctuation (noise) spectroscopy;
  • phase transitions;
  • low-dimensional molecular metals;
  • magnetism;
  • superconductivity

Abstract

Fluctuations (or noise) are often merely considered a nuisance, an unwanted disturbance limiting the accuracy of a scientific measurement. Electronic fluctuations, however, reveal hidden pieces of information not present in the mean quantity (the resistance) itself. Herein we describe resistance noise spectroscopy as a powerful new tool for investigating the low-frequency dynamics of electronic processes in low-dimensional organic conductors. Over the years, these molecular charge–transfer complexes have provided unprecedented model systems for exploring the physics of low-dimensional materials. The combination of low dimensionality with other parameters, specific to molecular conductors, sets the stage for Coulomb correlation effects to become relevant and, under certain circumstances, even to dominate the properties of the π-electron system. The combined effects of strong electron–electron and electron–phonon interactions give rise to the rich phenomenology of ground states encountered in these materials. To provide examples, we describe noise spectroscopy as a method to study the coupling of the correlated charge carriers to intramolecular modes of lattice vibrations and to investigate the inhomogeneous coexistence region of antiferromagnetic (Mott) insulating and superconducting phases.