Enhancing spin coherence in a pair of coupled spin 1/2 atoms assembled via STM

Detecting and controling individual spin centers and their interactions have been common interests for quantum and nanospintronic technologies. However, in solid-state nanostructures, the electron spin states are extremely fragile due to interaction with the electric and magnetic fluctuations arising from nearby electrodes or neighboring spins. In this work, we demonstrate that a singlet–triplet transition in a pair of antiferromagnetically coupled spin–1/2 atoms yields enhanced spin coherence compared to other transitions. We used scanning tunneling microscope to assemble two hydrogenated titanuim atoms on MgO(001). By selecting a spacing between two atoms that gives a large interaction energy, we obtain spin states having a high degree of protection from disrupting fields, and also provides thermal initialization into the singlet state. The spin coherence for the singlet–triplet transition is found to be ~3 times longer than other transitions, and the coherence time is further enhanced by reducing the interactions with tunneling electrons. Our work provides fundamental understandings of the spin dynamics in artificially built nanostructures. Additionally, these spin–1/2 Heisenberg antiferromagnets may serve as a promising architecture for quantum computation and simulation.