CHARGE TRANSPORT THROUGH A DOUBLE QUANTUM DOT IN THE PRESENCE OF DYNAMICAL DISORDER

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CHARGE TRANSPORTTHROUGH A DOUBLE QUANTUM DOT IN
THE PRESENCE OF DYNAMICAL DISORDER

• Jan Iwaniszewski
• with
• prof. Wlodzimierz Jaskólski,
• prof. Colin Lambert, Lancaster, UK
• Supported by The Royal Society, London

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Outline

• Charge transport in coupled semiconductor quantum
  dots
• applications
• description
• Dynamical disorder
• sources (defects)
• two-level fluctuator
• Charge transport in the presence of fluctuators
• description
• two-level system and fluctuator
• modification of the current
• Perspectives

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Description of the system

• Model
• single-level dots
• Coulomb blockade
• weak coupling to leads
• leads in thermal equilibrium

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Reduction of the description

• reduced evolution
• 2nd order perturbation
• infinitely fast relaxations in leads

Born-Markov approximation
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Rate equations
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Matrix calculus
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Dynamical disorder

• Sources of dynamical disorder
• phonon field
• fluctuations of impurities
• defects of the lattice
• Model - two-level fluctuator (TLF)
• the defect switches randomly between two discrete
  states ?D
• its dynamics is governed by dichotomous Markov
  noise with correlation time t1/2?

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Perturbed system
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Current in the presence of TLF
stationary current
(exact but cumbersome)

• slow fluctuator limit

fast fluctuator limit
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Stationary current for ?0
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Stationary current for ??0
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What next?

• Characteristic of the current
• coherency of the process
• spectral properties of the current
• Beyond the applied approximations
• detailed (quantum) description of the fluctuator
• detailed treatment of coupling to the leads
• two electrons transport weak Coulomb repulsion
  
• Related problems
• stochastic perturbation of energy levels
• multilevel quantum dots
• three- or multi- wells semiconductor structures
• The aim of research
• Optimal control of charge transport
• through semiconductor heterostructures

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The End