Probing and driving of spin and charge states in double quantum dot under the quench

Abstract

We have analyzed theoretically quenched dynamics of correlated double quantum dot (DQD) due to the switching “on” and “off” coupling to reservoirs. The possibility for controllable manipulation of charge and spin states in the double quantum dot was revealed and discussed. The proposed experimental scheme allows to prepare in DQD maximally entangled pure triplet state and to drive it to another entangled singlet state by tuning both applied bias and gate voltage. It was also demonstrated that the symmetry properties of the total system (double quantum dot coupled to electron reservoirs) allow to resolve the initially prepared two-electron states by detecting non-stationary spin-polarized currents flowing in both reservoirs and controlling the residual charge.

Tunneling current and noise of entangled electrons in correlated double quantum dot

“…We consider a well-known system of two coupled single-level quantum dots (impurity atoms) connected symmetrically to two electronic reservoirs (see Fig. 1 ) 54 . The Hamiltonian of the system, is written as a sum of the Hamiltonian describing the quantum dots the reservoir part and the tunneling Hamiltonian where ( ) is the spin-degenerate single-electron level and is the on-site Coulomb repulsion for double occupation of each quantum dot.…”

“…First of all we consider the system to be initially prepared in a single electron antisymmetric state. It can be done by means of the external laser pulse, when the resonant excitation of the coupled quantum dots system occurs (the frequency of the laser pulse is in the resonance with the antisymmetric single electron state energy level, consequently, the state becomes occupied) 54 . Another possibility to prepare system in the state is to use gates structure.…”

Correlated impurity complex in the asymmetric tunneling contact: an ideal system to observe negative tunneling conductivity

“…Several theoretical approaches are usually used for analysis of the electron transport through the atomic-scale devices. Among them are approaches based on the Hubbard operators 41,42 , pseudo-particle approach 43,44 , well known non-equilibrium Keldysh diagram technique or equations of motion formalism. The problem of Hubbard operators approach deals with the non-trivial commutation rules for Hubbard operators, so it is rather difficult to consider high order correlations only by means of this approach.…”

“…That is why in 41,42 authors tried to combine non-equilibrium diagram technique with theoretical approach based on the Hubbard operators. Theoretical scheme based on the pseudo-particles seems to be more convenient in some cases as it allows to generalize Keldysh diagram technique with full account of constraint on the total number of pseudo-particles 43,44 . Here we tried to avoid all these difficulties introducing non-equilibrium Green functions in the operator form and performing averaging over localized electron states at the very last stage in the equations of motion.…”

Universal power law decay of spin polarization in double quantum dot

“…In a double * vmantsev@gmail.com † smirnov@mail.ioffe.ru quantum dot the exchange interaction [20,21] and electron hopping [22,23] are also important and affect the spin dynamics. We stress, that we consider only hopping between the QDs, but not to the contacts or substrate [24,25]. The interplay between exchange interaction, hopping and hyperfine interaction can be hardly investigated for the large spin ensembles.…”