Spin Blockade in a Colloidal CdSe Quantum Dot Solid
A University of Chicago MRSEC team led by Philippe Guyot-Sionnest and Woowon Kang have been investigating the transport properties of colloidal quantum dots under magnetic field.
They uncovered two effects of the magnetic field on the conductance of the quantum dot solids. One effect is the wavefunction squeezing under large magnetic field (10T) and low temperature which reduces overlap and thus conductivity.
The other effect is a spin blockade in which electrons of spin quantized with the external field cannot pass by a dot already occupied by an electron of the same spin orientation, as shown in the schematic at left. At low magnetic field spin (0.2T) weak hyperfine coupling can randomize the spins, favoring transport.
This type of nanomaterial may provide components of future technologies based on spin control with potential applications in information storage and computing.
"Magnetoresistance of n-type quantum dot solids," D. Yu, B.L. Wehrenber, I. Yang, W. Kang, P. Guyot-Sionnest, Appl. Phys. Lett. 88. 072504 (2006).