Würzburg ToCoTronics Colloquium

The interplay between the electronic degrees of freedom − spin, charge and orbital – enriched with topological and chiral concepts give rise to exciting physics with thrilling and intriguing phenomena that span several orders of magnitude in length and timescales. The impact on potential quantum- and topology-based devices is heavily explored with the aim of overcoming major obstacles of the holy trinity of information technology, namely high-performance, compact data storage and energy saving, which require the discovery of novel concepts of bits, their stability, manipulation and efficient detection.

In this colloquium, I will discuss new magneto-transport phenomena emerging across various dimensions by focusing on all-electrical readout of single magnetic atoms on surfaces and topological two-dimensional solitonic spin-textures, Skyrmions. In particular, I will demonstrate that zero-bias anomalies detected by scanning tunneling spectroscopy on adatoms and interpreted in the last 25 years as Kondo features are in fact spin-orbit induced phenomena, which lead to gapped spin-excitations due to a finite magnetic anisotropy energy [1]. These intrinsic excitations can have anomalous transport signatures [2,3] with the possibility of overlapping with a dominant new many-body feature, the spinaron, resulting from the interaction of electrons and spin-excitations [1]. From the infinitely small, I will then zoom out to address skyrmions and introduce a new family of magnetoresistances, which enable the electrical reading of the ever-increasing number of predicted and discovered topological entities by discerning their chiral attributes in current-perpendicular-to-plane sensing devices. The detection mechanisms are categorized in terms of the presence (or not) of non-collinear magnetism, spin-orbit interaction and their concomitant intertwining [4,5]. Finally, I will explore the impact of atomic defects, which simultaneously enable new detection paradigms [6] and design the energy-landscape of single skyrmions by imposing a universal shape as function of the defect's electron filling [7].

[1] J. Bouaziz, F. S. M. Guimaraes, S. Lounis, Nat. Commun. 11, 6112 (2020)
[2] S. Brinker, F. Küster, S. S. P. Parkin, P. Sessi, S. Lounis, Science Adv. 8, eabi7291 (2022)
[3] F. Küster, A. M. Montero, F. S. M. Guimaraes, S. Brinker, S. Lounis, S. S. P. Parkin, P. Sessi, Nat. Commun. 12, 1108 (2021)
[4] I. L. Fernandes, S. Blügel, S. Lounis, Nat. Commun. 13, 1576 (2022)
[5] D. M. Crum, M. Bouhassoune, J. Bouaziz, B. Schweflinghaus, S. Blügel, S. Lounis, Nat. Commun. 6, 8541 (2015)
[6] I. L. Fernandes, M. Bouhassoune, S. Lounis, Nat. Commun. 11, 1602 (2020)
[7] I. L. Fernandes, J. Bouaziz, S. Blügel, S. Lounis, Nat. Commun. 9, 4395 (2018)

This talk is also broadcasted via zoom. To enter the meeting, follow the link:
https://uni-wuerzburg.zoom.us/s/63035236463