On the concept of effective temperature in current carrying quantum critical states

Abstract

Quantum criticality has attracted considerable attention both theoretically and experimentally as a way to describe part of the phase diagram of strongly correlated systems. A scale-invariant fluctuation spectrum at a quantum critical point implies the absence of any intrinsic scale. Any experimental probe may therefore create an out-of-equilibrium setting; the system would be in a non-linear response regime, which violates the fluctuation-dissipation theorem. Here, we study this violation and related out-of equilibrium phenomena in a single electron transistor with ferromagnetic leads, which can be tuned through a quantum phase transition. We review 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. In particular, we explore the concept of effective temperature as a means to extend the fluctuation-dissipation theorem into the non-linear regime.

4 pages, 2 figures; Manuscript for Proceedings of the International Conference on Quantum Criticality and Novel Phases (QCNP09, Dresden)

References in corpus (8)

• Fermi-liquid instabilities at magnetic quantum phase transitions
• Quantum Criticality in Heavy Fermion Metals
• NRG study of the Kondo effect in the presence of itinerant-electron ferromagnetism
• Quantum critical properties of the Bose-Fermi Kondo Model in a large-N limit
• Quantum Criticality in Ferromagnetic Single-Electron Transistors
• Quantum Criticality out of Equilibrium: Steady State in a Magnetic Single-Electron Transistor
• Bose-Fermi Kondo model with Ising anisotropy: cluster-Monte Carlo approach
• Magnetic Single-Electron Transistor as a Tunable Model System for Kondo-Destroying Quantum Criticality

Cited by in corpus (8)

• Hawking Radiation and Non-equilibrium Quantum Critical Current Noise
• Local Temperatures Out of Equilibrium
• Local quantum criticality out of equilibrium - effective temperatures and scaling in the steady state regime
• Steady-state dynamics and effective temperatures of quantum criticality in an open system
• Non-equilibrium quantum transport through a dissipative resonant level
• Nonequilibrium quantum criticality in bilayer itinerant ferromagnets
• Nonlinear thermoelectric response of quantum dots: renormalized dual fermions out of equilibrium
• Non-linear quantum critical dynamics and fluctuation-dissipation ratios far from equilibrium