title: Control and detection of singlet-triplet mixing in a random nuclear field.
abstract: We observed mixing between two-electron singlet and triplet states in a double quantum dot, caused by interactions with nuclear spins in the host semiconductor. This mixing was suppressed when we applied a small magnetic field or increased the interdot tunnel coupling and thereby the singlet-triplet splitting. Electron transport involving transitions between triplets and singlets in turn polarized the nuclei, resulting in marked bistabilities. We extract from the fluctuating nuclear field a limitation on the time-averaged spin coherence time T2* of 25 nanoseconds. Control of the electron-nuclear interaction will therefore be crucial for the coherent manipulation of individual electron spins.
authors.affiliation: Kavli Institute of Nanoscience, Delft University of Technology, Post Office Box 5046, 2600 GA Delft, Netherlands.
authors.forename: F H L
authors.initials: FH
authors.lastname: Koppens
authors.forename: J A
authors.initials: JA
authors.lastname: Folk
authors.forename: J M
authors.initials: JM
authors.lastname: Elzerman
authors.forename: R
authors.initials: R
authors.lastname: Hanson
authors.forename: L H Willems
authors.initials: LH
authors.lastname: van Beveren
authors.forename: I T
authors.initials: IT
authors.lastname: Vink
authors.forename: H P
authors.initials: HP
authors.lastname: Tranitz
authors.forename: W
authors.initials: W
authors.lastname: Wegscheider
authors.forename: L P
authors.initials: LP
authors.lastname: Kouwenhoven
authors.forename: L M K
authors.initials: LM
authors.lastname: Vandersypen