Séminaire AXE 1 – Sciences et Matériaux Quantiquesprésenté par : Alexina Ollier

Speaker: Alexina Ollier, Center for Quantum Nanoscience (QNS), Institute for Basic Science (IBS), Seoul, South Korea

Here, we report on imaging the spin texture of triple-Q magnetic order of Co1/3TaS2. The sample
was measured with a low temperature STM (T=6K) under ultra-high vacuum with normal
and spin-polarized tips. The STM images with the normal tip show the triangular lattice of the
sample. The spin-polarized (SP) tip shows an additional symmetry related to the triple-Q
ordering. In addition to that, the SP STM images revealed different spin textures with respect
to the tip-spin orientation. The analysis suggests the presence of a phase difference between the
tip and the triple-Q ordering of the sample. This work gives a new insight into the exploration of
chiral magnetic ordering with topological Hall effect using scanning probe microscopy.

Séminaire de l’Axe 2 “Nanosciences pour le Vivant” présenté par : Thomas PONS

Thomas PONS (Laboratoire de Physique et d’Etudes des Matériaux, ESPCI, Sorbonne Université, Paris (LPME))

Fluorescent biodetection assays using pairs of fluorescent donors and acceptors interacting via Förster Resonant Energy Transfer (FRET) are appealing thanks to their ease of use, versatility and specificity. They are however limited in sensitivity due in particular to their limited distance range. We are currently developing a novel type of biodetection assay based on energy transfer using Whispering Gallery Modes (WGM) from optical microcavities excited by fluorescent quantum dots as donors and polymeric dye-loaded nanoparticles (dyeNP) as acceptors. The high quality factor of the microcavities enables a strong enhancement of energy transfer to dyeNP acceptors placed within their evanescent field. In particular, we have studied their interactions in a model system using streptavidin-coated microcavities and biotinylated dyeNPs. Upon their specific biomolecular interaction, the dyeNP bind to the microcavity surface, leading to efficient energy transfer, with a typical sensitivity in the fM range, 4-6 orders of magnitude more sensitive than typical FRET assays. We further demonstrate the ultrasensitive detection of DNA oligonucleotides.

Contact :Damien MERTZ  damien.mertz@ipcms.unistra.fr

Séminaire Axe 1- “Sciences et Matériaux Quantiques” présenté par : Cosimo Gorini

Charge currents may be generated by pure spin injection via the spin galvanic effect, also
referred to as “inverse Rashba – Edelstein effect”, and/or the inverse spin Hall effect. In a
typical spin pumping setup consisting of a injector, e.g. a driven magnetic electrode, and a
converter, a metallic spin-orbit coupled system, both effects contribute to the conversion. If
however the converter is 2D only the spin galvanic channel is available. This is notably the
relevant scenario for 2D dimensional electron gases at oxide interfaces.
Recent experiments at such interfaces show strongly anisotropic spin- (and orbit-) to charge
conversion [1], which I will explain in terms of the “tunneling anisotropic spin galvanic effect”
[2]. I will also show how intrinsic time scales heavily affect such conversion in the ultrafast
regime [3].

References
[1] El Hamdi et al., Nat. Phys. 19, 1855 (2023)
[2] Fleury et al., Phys. Rev. B 108, L081402 (2023)
[3] El Hamdi et al., Phys. Rev. B 110, 054412 (2024)

Contact: Arnaud GLOPPE (arnaud.gloppe@ipcms.unistra.fr) – Guillaume SCHULL (schull@unistra.fr)