Descripción del proyecto
Investigación de sistemas cuánticos no lineales en desequilibrio
El teorema de la fluctuación-disipación es un principio fundamental de la física, que vincula la respuesta de un sistema a perturbaciones externas (disipación) con sus fluctuaciones naturales en equilibrio. El teorema ofrece una visión del comportamiento microscópico de los sistemas macroscópicos y mejora la comprensión de los procesos irreversibles. El equipo del proyecto NSECPROBE, financiado con fondos del Consejo Europeo de Investigación, tiene como objetivo probar empíricamente los últimos avances teóricos que generalizan el teorema a sistemas cuánticos no lineales alejados del equilibrio. Los investigadores de equipo estudiarán estos sistemas cuánticos de fuerte interacción, mediante la medición de las fluctuaciones de corriente y las respuestas disipativas cuando estos sistemas se ven influidos por fuerzas externas. Además, el equipo desarrollará nuevos métodos basados en la luz de microondas que puedan hacer frente a grandes valores de impedancia.
Objetivo
The fluctuation-dissipation theorem is a prominent milestone in Physics: It links the dissipative response of a physical system to its fluctuations, and provides a microscopic understanding of macroscopic irreversibility. Recent theoretical advances that have generalized the original fluctuation-dissipation theorem to non-linear quantum systems even far from equilibrium, ask for an experimental test, which is the aim of the project. We will measure the current fluctuations and dissipative response of driven quantum systems whose non-linearity arises from strong interactions. We will exploit the flexibility offered by nano-patterned high purity 2D electron gases in order to realize single electron channels in different regimes: 1/ interacting strongly with a single electromagnetic mode (Dynamical Coulomb Blockade of a quantum point contact), 2/ interacting with a single magnetic impurity (Kondo effect in quantum dots), 3/ driving the 2D gas in the fractional quantum Hall effect where current is carried by strongly correlated 1D channels prototypical of Luttinger liquids. Last, we will address a fundamental issue raised in the early days of quantum mechanics: how long does it take for a particle to cross a classically forbidden barrier? While Wigner-Smith’s theorem links the issue to the density fluctuations within the barrier, the fluctuation-dissipation theorem links it further to a quantum relaxation resistance. A full investigation of fluctuation-dissipation relations including quantum effects requires measurements at frequencies hf>k_BT. With the available dilution refrigeration techniques it implies measuring in the few GHz range. Since quantum conductors have an impedance h/e^2~25.8 kohm much larger than the 50ohm impedance of microwave components, new microwave methods able to deal with large impedance values will be developed. They will be based on the extension to finite magnetic field of the wide-band impedance matching methods recently developed by the PI.
Ámbito científico
Programa(s)
Régimen de financiación
ERC-STG - Starting GrantInstitución de acogida
75015 PARIS 15
Francia