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.
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.
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)
Abhishake MONDAL (Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore)
Abstract :
The pursuit of smart multifunctional materials with stimuli-responsive magnetic and optical response has drawn escalating interest in both fundamental science and potential applications to switches, sensors, and intelligent devices.1 One of the appealing feature of such materials is the tunability of their physical property via chemistry, where the linking structure and physical properties can be modulated in practically infinite ways, which gives them an edge over the solid-state magnetic materials (Figure 1, a).2 The field of molecular bistable systems is rapidly budding towards utilizing these molecule-based magnetic materials in physics-driven and nanotechnology-driven fields (Figure 1, b).
Figure 1: a) Stimuli-responsive molecular bistable systems and b) Application areas where these systems are actively studied for developing devices
Here, I will briefly cover the exciting field of Molecular Magnetism and will specifically focus on three most important aspects of Molecular Magnetism being pursued in my laboratory i) Spin Crossover (SCO) materials3 ii) Metal-to-Metal Electron Transfer Systems (MMET)4 and iii) Single Molecule Magnets (SMM).5 Lastly, I shall discuss the application of these bistable systems in developing ring-resonator devices for Photonics Application, molecular break junctions and microelectromechanical systems.
Acknowledgments: I thank the Indian Institute of Science (IISc), Bangalore, India, and the Ministry of Human Resource Development (MHRD), Ministry of Education (MoE), Government of India, IISc-Start-up Research Grant, the Department of Science and Technology, Mission on Nano Science and Technology (Nano Mission), Scheme for Transformational and Advanced Research in Sciences (STARS, MHRD), Council of Scientific and Industrial Research (CSIR) for the research fundings.
