第116回先端計測オープンセミナー

2017年12月5日 (火) 11:00~12:00

国立研究開発法人 物質・材料研究機構 
千現地区 研究本館8階 中セミナー室
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Dr. Yujeong Bae (Center for Quantum Nanoscience, Institutie for Basic Science (IBS),Seoul/IBM Almaden Research Center, San Jose/Department of Physics, Ewha Womans University)

Using ESR-STM as a tool to build quantum dimers

Abstract: Detecting and controlling the individual spin centers and their interactions have been common interests for the quantum and nanospintronic technologies. However, in the 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, for spin-1/2 antiferromagnets, we demonstrate a singlet-triplet transition facilitates resonant control of the spin states with enhanced spin coherence. We built dimers of hydrogenated-titanium (Ti) atoms, which have spin of 1/2, on MgO(001) and implemented electron spin resonance (ESR) on them in scanning tunneling microscope (STM). The Ti atoms separated by ~1 nm are Heisenberg exchange coupled with antiferromagnetic alignment. This spin configuration enables us to achieve enhanced spin coherence using the transition between singlet and triplet states, which are known to be more immune to the spin decoherence sources. By selecting a spacing between two atoms that gives a large interaction energy, we could provide the spin states a high degree of protection from disrupting fields with better thermal initialization into the singlet state. The spin coherence for the singlet-triplet transition is found to be ~3 times longer than other transitions in the system and could be 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.