Control and detection of singlet-triplet mixing in a random nuclear field.
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.
Koppens
F H L
FH
Kavli Institute of Nanoscience, Delft University of Technology, Post Office Box 5046, 2600 GA Delft, Netherlands.
Folk
J A
JA
Elzerman
J M
JM
Hanson
R
R
van Beveren
L H Willems
LH
Vink
I T
IT
Tranitz
H P
HP
Wegscheider
W
W
Kouwenhoven
L P
LP
Vandersypen
L M K
LM