Spin and e-e interactions in quantum dots: leading order corrections to universality and temperature effects

GONZALO USAJ; U BARANGER, HAROLD

PHYSICAL REVIEW B - CONDENSED MATTER AND MATERIALS PHYSICS

Año: 2002 vol. 66 p. 15533 - 15533

0163-1829

   We study the statistics of the spacing between Coulomb blockade conductance peaks in quantum dots withlarge dimensionless conductance g. Our starting point is the ‘‘universal Hamiltonian’’—valid in the g→inftylimit—which includes the charging energy, the single-electron energies described by random matrix theory ,and the average exchange interaction. We then calculate the magnitude of the most relevant finite g corrections,namely, the effect of surface charge, the ‘‘gate’’ effect, and the fluctuation of the residual e-e interaction. Theresulting zero-temperature peak spacing distribution has corrections of order1 / g. For typical values of thee-e interaction (rs~1) and simple geometries, theory predicts an asymmetric distribution with a significanteven/odd effect. The width of the distribution is of order 0.3 , and its dominant feature is a large peak for theodd case, reminiscent of the function in the g→ limit. We consider finite temperature effects next. Onlyafter their inclusion is good agreement with the experimental results obtained. Even relatively low temperaturecauses large modifications in the peak spacing distribution: i its peak is dominated by the even distribution atk BT 0.3 at lower T a double peak appears , ii the even/odd effect is considerably weaker, iii thefunction is completely washed out, and v fluctuation of the coupling to the leads becomes relevant. Experiments aimed at observing the T 0 peak spacing distribution should therefore be done at k BT 0.1 for typical values of the e-e interaction.