Atomic-scale spin-sensing with a single molecule at the apex of a scanning tunneling microscope

DIPC Seminars

Benjamin VERLHAC
Donostia International Physics Center
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Atomic-scale spin-sensing with a single molecule at the apex of a scanning tunneling microscope This work that will be presented is in the context of the study of surface magnetism, which knew great developments these last years thanks to the scanning tunneling microscope (STM). Its purpose was to demonstrate that a simple molecule, the nickelocene [Ni(C5H5)2], can be attached to the STM tip apex to produce a molecular and magnetic probe-tip [1]. We show that, compared to other systems studied by STM, the magnetic properties of nickelocene in gas phase are preserved upon adsorption on a metallic electrode, when it is adsorbed either on a copper surface or on the copper terminated STM tip apex [2]. We show also that the value of its spin can be tuned by contacting the tip adsorbed molecule onto the Cu(100) surface, triggering a controllable Kondo resonance[3]. However, the main result that will be presented is the use of the tip adsorbed nickelocene as a probe of the magnetism of a single atom on Cu(100) and a ferromagnetic surface. Indeed, nickelocene presents spin excitations which correspond to a change of spin momentum and are sensible to neighboring magnetism. The magnetic sensibility of our technique is due to the exchange coupling between the molecule on the tip and the magnetic object. Due to a traceable variation of this coupling by only a few picometers movement of the tip, we can achieve atomic and subsurface resolution on the ferromagnetic surface. Another aspect is that spin excitations allow also to discriminate the two electron spin populations in the tunnel junction transport, permitting an atomically resolved mapping of spin polarized transport. References: [1] Verlhac et al., Science 366, 6465 (2019) [2] Ormaza et al., Nano Letters 17,1877 (2017) [3] Ormaza et al., Nature Communications 8, 1974 (2017) Host: Choi Deung-Jang