Department of Physics, The Hong Kong University of Science and Technology , Hong Kong, China.
Department of Physics, Southern University of Science and Technology of China , Nanshan District, Shenzhen, Guangdong 518055, China.
ACS Nano. 2017 Jun 27;11(6):6295-6300. doi: 10.1021/acsnano.7b02567. Epub 2017 May 18.
Spin-crossover (SCO) molecules are thought to be ideal systems for molecular spintronics when SCO can be precisely controlled at the single-molecule level. This is demonstrated here in the single-molecule junctions of Fe-porphyrin formed in a scanning tunneling microscope. Experimentally, we find that the junctions feature a zero-bias resonance in molecular conductance associated with the Fe spin center. When mechanically stretching or squeezing the junctions by adjusting the tip height, the line shape of the zero-bias resonance varies reversibly. First-principles calculations reveal that widening the junction gap by 2 Å transforms the macrocyclic core hosting the Fe center from a saddle to a planar conformation. This conformational change shortens the Fe-N bonds by 3%, which changes the Fe spin state from S = 2 to S = 1.
自旋交叉（SCO）分子被认为是分子自旋电子学的理想体系，因为当 SCO 可以在单分子水平上精确控制时。这在扫描隧道显微镜中形成的 Fe-卟啉单分子结中得到了证明。实验上，我们发现结的分子电导中存在与 Fe 自旋中心相关的零偏共振。当通过调整针尖高度机械拉伸或压缩结时，零偏共振的线形状会可逆地变化。第一性原理计算表明，通过将结间隙加宽 2 Å，将容纳 Fe 中心的大环核心从马鞍形变为平面构象。这种构象变化使 Fe-N 键缩短 3%，从而改变 Fe 自旋态从 S = 2 到 S = 1。
