Berlin 2015 – scientific programme

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BP: Fachverband Biologische Physik

BP 34: Statistical Physics of Biological Systems II (joint BP/DY/CPP)

BP 34.6: Talk

Wednesday, March 18, 2015, 10:45–11:00, H 1028

Single molecule measurement of the effective temperature in nonequilibrium steady states — •Eckhard Dieterich¹, Joan Camunas-Soler^2,3, Marco Ribezzi-Crivellari^2,3, Udo Seifert¹, and Felix Ritort^2,3 — ¹II. Institut für Theoretische Physik, Universität Stuttgart, Germany — ²Departament de Física Fonamental, Universitat de Barcelona, Spain — ³CIBER-BBN de Bioingeniería, Biomateriales y Nanomedicina, Instituto de Salud Carlos III, Madrid, Spain

Temperature is a crucial concept for equilibrium systems. For glassy systems, it has been extended to the nonequilibrium regime as an effective quantity showing up in the fluctuation-dissipation theorem. However, direct supporting experimental evidence remains scarce. Here, we present the first direct experimental demonstration of the effective temperature by measuring correlations and responses in single molecules in nonequilibrium steady states generated under external random forces. We combine experiment, analytical theory and simulations for systems with different levels of complexity ranging from a single bead in an optical trap to two-state and multiple-state DNA hairpins. From these data, we can extract a unifying picture for the existence of an effective temperature based on the relative order of various time-scales characterizing intrinsic relaxation and external driving. Our study thus introduces driven small systems as a fertile ground to address fundamental concepts in statistical physics, condensed matter physics and biophysics.