Transport spectroscopy of non-equilibrium many-particle spin states in self-assembled quantum dots.
Bottom Line:
For these systems, great progress has been made in addressing spin states by optical means.The excitation spectra of the one- (QD hydrogen), two- (QD helium) and three- (QD lithium) electron configuration are shown and compared with calculations using the exact diagonalization method.An exchange splitting of 10 meV between the excited triplet and singlet spin states is observed in the QD helium spectrum.
View Article:
PubMed Central - PubMed
Affiliation: Fakultät für Physik and CeNIDE, Universität Duisburg-Essen, Lotharstraße 1, Duisburg 47048, Germany.
ABSTRACT
Show MeSH
Self-assembled quantum dots (QDs) are prominent candidates for solid-state quantum information processing. For these systems, great progress has been made in addressing spin states by optical means. In this study, we introduce an all-electrical measurement technique to prepare and detect non-equilibrium many-particle spin states in an ensemble of self-assembled QDs at liquid helium temperature. The excitation spectra of the one- (QD hydrogen), two- (QD helium) and three- (QD lithium) electron configuration are shown and compared with calculations using the exact diagonalization method. An exchange splitting of 10 meV between the excited triplet and singlet spin states is observed in the QD helium spectrum. These experiments are a starting point for an all-electrical control of electron spin states in self-assembled QDs above liquid helium temperature. Related in: MedlinePlus |
Related In:
Results -
Collection
License getmorefigures.php?uid=PMC3105341&req=5
Mentions: For a thorough identification of the different resonances, we have calculated the many-particle energy states in a 2D harmonic oscillator for n=1, 2 and 3 electrons using the exact diagonalization method, which provides numerically exact solutions2425. This yields the many-particle states of the interacting electrons in terms of superpositions of single-particle Slater determinants. Their coefficients give the probability of single-particle configuration to be found. The level spacing ħω=52 meV was taken from the single-particle spectrum in Figure 2b. The effective mass and the dielectric constant were chosen to be m*=0.067m0 and ɛr=16, respectively, which go into the calculations by the single adjustable parameter16. In Figure 4, the calculated energies for the GS and the first few excited states are listed, together with the leading terms in the Slater determinant expansion (relative contributions given in %). Each level diagram represents an eigenstate to a total spin and total angular momentum including the corresponding Slater determinants with permuted orbital configuration. For each degenerate spin and angular momentum multiplet, only one representative is shown. Also shown are the experimental energies determined using the resonance condition for tunnelling En−En−1=eΔVp/λ and choosing the zero point of the energy scale such that the single-electron GS corresponds to E1GS=E(s1)=52 meV. |
View Article: PubMed Central - PubMed
Affiliation: Fakultät für Physik and CeNIDE, Universität Duisburg-Essen, Lotharstraße 1, Duisburg 47048, Germany.