Regensburg 2010 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 38: CE: Quantum-Critical Phenomena 2

TT 38.2: Vortrag

Freitag, 26. März 2010, 10:30–10:45, H18

The concept of effective temperature in current carrying quantum critical states — •Stefan Kirchner¹ and Qimiao Si² — ¹Max Planck Institut fuer Physik komplexer Systeme — ²Physics & Astronomy, Rice University, Houston, Texas

At a quantum critical point, a scale-invariant fluctuation spectrum implies the absence of intrinsic energy scales. The system is therefore readily driven out of equilibrium. The resulting non-linear response regime violates the fluctuation-dissipation theorem. We study the out-of equilibrium phenomena in a single electron transistor with ferromagnetic leads, which can be tuned through a quantum phase transition[1]. We consider the breakdown of the fluctuation-dissipation theorem and study the universal behavior of the fluctuation dissipation relation of various correlators in the quantum critical regime[2]. In particular, we explore the concept of effective temperature as a means to extend the fluctuation-dissipation theorem into the non-linear regime[3]. Such effective temperatures were introduced in the context of steady states in chaotic systems, and successfully used for non-stationary states in glassy systems.

[1] S. Kirchner et al.,PNAS 102, 18824 (2005).

[2] S. Kirchner and Q. Si, PRL 103, 206401 (2009).

[3] S. Kirchner and Q. Si, arXiv:0909.3925 (2009).