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Theme 3 colloquium: 'Sub-molecular fluorescence microscopy with STM' & 'Atomic-scale spin sensing with a single-molecule at the apex of a scanning tunneling microscope' (Lecture)

Tuesday 19 November 2019Add to my calendar
from 16:00
Guillaume Schull and Laurent Limot (Institut de Physique et de Chimie des Matériaux de Strasbourg, France)

Guillaume SchullAbstract 'Sub-molecular fluorescence microscopy with STM' - Guillaume Schull

The electric current traversing the junction of a scanning tunneling microscope (STM) may lead to a local emission of light that can be used to generate sub-molecularly resolved fluorescence maps of individual molecules. Combined with spectral selection and time-correlated measurements, this hyper-resolved fluorescence microscopy approach allowed us to scrutinize the vibronic structure of individual molecules [1] in a very similar way than in the recent TERS reports, without requiring an optical excitation. We used this approach to characterize the photonics properties of charged species [2] and to track the motion of hydrogen atoms within free-based phthalocyanine molecules [3].

Together with other recent reports [4,5], these results constitute an important step towards photonic measurements with atoms-scale resolution.

Artistic view of a single ZnPc molecule excited with STMfig.: Artistic view of a single ZnPc molecule excited with STM

[1] B. Doppagne et al., Phys. Rev. Lett. 118, 127401 (2017)
[2] B. Doppagne et al. Science, 361, 251 (2018)
[3] B. Doppagne et al. unpublished
[4] Y. Zhang et al. Nature 531, 623 (2016)
[5] H. Imada et al., Nature 538, 364 (2016)

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

Recent advances in scanning probe techniques rely on the chemical functionalization of the probe-tip termination with single molecules weakly connected to the metallic apex. Information, otherwise inaccessible with a metallic tip, can be gathered in this way [1]. The success of this approach opens the tantalizing prospect of introducing spin sensitivity through the probe-tip termination by a magnetic molecule. Here, we use a nickelocene-terminated tip (Nc-tip), which offers the possibility of producing spin excitations on the tip apex of a scanning tunneling microscope (STM) [2,3]. We show that when the Nc-tip is a hundred pm away from point contact with a surface-supported object, magnetic effects may be probed through changes in the spin excitation spectrum [4] of nickelocene. We use this detection scheme to determine the exchange field and the spin polarization of the sample with atomic-scale resolution. Our findings demonstrate that the Nc-tip is a powerful probe for investigating surface magnetism with STM, from single magnetic atoms to surfaces as we exemplify in this talk.

[1] L. Gross, F. Mohn, N. Moll, P. Liljeroth, G. Meyer, Science 325, 1110 (2009). [2] M. Ormaza, N. Bachellier, M. N. Faraggi, B. Verlhac, P. Abufager, P. Ohresser, L. Joly, M. Romeo, F. Scheurer, M.-L. Bocquet, N. Lorente, L. Limot, Nano Lett. 17, 1877 (2017).
[3] M. Ormaza, P. Abufager, B. Verlhac, N. Bachellier, M. L. Bocquet, N. Lorente, L. Limot, Nat. Commun. 8, 1974 (2017).
[4] A. J. Heinrich, J. A. Gupta, C. P. Lutz, and D. M. Eigler, Science 306, 466 (2004).