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Thermal and quantum crossovers in out-of-equilibrium quantum dots

Thermal and quantum crossovers in out-of-equilibrium quantum dots. Slava Kashcheyevs (Uni Latvia). Thermo 2013, RWTH Aachen, November 25, 2013. VK and J.Timoshenko, Phys. Rev. Lett. 109 , 216801(2012) L. Fricke et al , Phys. Rev. Lett. 110 , 126803 (2013)

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Thermal and quantum crossovers in out-of-equilibrium quantum dots

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  1. Thermal and quantum crossovers in out-of-equilibrium quantum dots Slava Kashcheyevs (Uni Latvia) Thermo 2013, RWTH Aachen, November 25, 2013 VK and J.Timoshenko, Phys. Rev. Lett. 109, 216801(2012) L. Fricke et al, Phys. Rev. Lett. 110, 126803 (2013) S. S Fahlvik Svensson et al, New J Phys 15, 105011 (2013)

  2. Main topic of the talk • “Disequilibration” = gradual decoupling of a finite system from macroscopic environment • An important part of protocol for: • on-demand few-particle sources • microscopic heat engines/pumps • selective quantum state preparation • …

  3. Theorist’s trade-offs Quantum coherence Non-equillibrium Coulombinteractions Coulombinteractions

  4. Time-dependent resonance level • Single spinless level coupled to a Fermi lead • Exactly solvable for any • Phase memory can be neglected if: equilibrium (coupling=const) Jauho,Meir,Wingreen’94 - timescale of decoupling,e.g. non-Markovian effects if violated!

  5. Disequilibration of a single level Flensberg,Pustilnik,Niu’1999 VK,Timoshenko,’2013 “Plunger-to-barrier” ratio (crosscoupling strength) Δptbbreaks particle-hole symmetry!

  6. Quantum disequilibration crossover decoupled adaiabtic Non-perturbative, non-Markovian asymptotics dominates the tail!

  7. Charge pump as disequilibration device Moving the decoupling point determines the captured charge (=moves ) LOAD V1 Decouple I/(ef) 1 capture 0 capture 1 1 Couple 0 V2 UNLOAD 0 V2 • capture • isolate • eject Data: L.Fricke, Uni.Hannover

  8. Theorist’s trade-offs Quantum coherence Non-equillibrium

  9. Quantum coherence Quantum coherence Non-equillibrium Coulombinteractions Coulombinteractions

  10. Landau-Zener-Stückelberg Need both excitation and backtunneling: Balancing the interferometer!

  11. Two-path nterference • Non-adiabatic excitation (Landau-Zener) • Adiabatic “elevator”

  12. Quantum coherence Non-equillibrium Coulombinteractions

  13. Exact NEGF solution Quantum coherence Non-equillibrium Coulombinteractions

  14. Markov rate equations Quantum coherence Non-equillibrium Coulombinteractions - ?

  15. Grand canonical ensemble • Adiabatic side of the disequlibration crossover:

  16. Load Hold Detect!

  17. Disequilibration kinetics • Rate equations for the slow degree of freedom: • detailed balance: • Transitions n-1↔n “freeze” sequentially as Fermi function See M. Esposito’s talk!

  18. Backtunneling limit: decay cascade Adiabatic constant Non-adiabatic decay • Final capture probability: follows equilibium Backtunneling onset VK and B.Kaestner, Phys. Rev. Lett. 104, 186805 (2010)

  19. Decay cascade model: gradual decoupling Simple fitting formulas if backtunneling dominates Data: PTB group;Hohls et al, PRL’2012 Rescaled gate voltage

  20. Two “universal” limits • Generalized grand canonical (thermal) • Phenomenological parametric ansatz • Generalized decay cascade (athermal) L. Fricke et al, Phys. Rev. Lett. 110, 126803 (2013)

  21. Quantum coherence Quantum dotdisequilibrationchallenges Non-equillibrium Coulombinteractions • Equlibrium Anderson model is rich & well-studied • RG for gradual quenches? • Dynamical scaling near “quantum critical” point? • Spin and orbital intradot excitations: • Spin-charge separation in mixed-valence/Kondo transition • See talk by Heiner Linke! VK, Karrasch, Hecht, Weichselbaum, Meden, Schiller PRL’09

  22. Thank you!

  23. S. S Fahlvik Svensson et al, New J Phys 15, 105011 (2013)

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