Exchange interaction and stability diagram of coupled quantu(8)

The charge stability diagram for two coupled quantum dots containing up to two electrons is computed in magnetic fields. One- and two-particle Schroedinger equations are solved by exact diagonalization to obtain the chemical potentials and exchange energy

andtwo-electronHamiltonian.Twointer-dotseparationsd=50and60nmcorrespondingtostrongandweakinter-dotcouplingwereconsidered.Wefoundthatintheweak-couplingregimethecurvatureofthechemicalpotentialµ(2)islargerthanthatoneofµ(1)whileinthestrong-couplingcasethesituationisreversed.Hence,byanalyzingthechemicalpotentialvariationscausedbyexternalbiasesandmagnetic elds,itispossibletodistinguishbetweenstrongandweakinter-dotcoupling,evenifthecurvaturesareofthesameorderinbothcases.Theevolutionofthestabilitydiagramsinmagnetic eldsconformstothegeneralideaofenhancedelectronlocalizationwithincreasing eldstrength.Theexchangeenergiesextractedfromthestabilitydiagramsshowedthatthesevaluesaresigni cantlyoverestimatedwhencomparedwithnumericallyexactdata.

ThisworkissupportedbyDARPAQUISTprogramthroughAROGrantDAAD19-01-1-0659.TheauthorsthanktheMaterialComputationalCenterattheUniversityofIllinoisthroughNSFGrantDMR99-76550.LXZthankstheComputerScienceandEngineeringFellowshipProgramattheUniversityofIllinoisforsupport.

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