Poster presentation

On-surface synthesis of triangulene chains on a proximitized superconductor
Katerina Vaxevani¹, Dongfei Wang¹, Stefano Trivini¹, Jon Ortuzar¹, Jose Ignacio Pascual^1,2

1 CIC nanoGUNE-BRTA, 20018 Donostia-San Sebastian, Spain
2 Ikerbasque, Basque Foundation for Science, 48013 Bilbao, Spain

Bridging magnetism and superconductivity has always been a fascinating field where many rich physical phenomena emerge. For example, in the past years, there have been theoretical proposals[1-3], as well as experimental evidence[4] for the realization of Majorana fermions in magnetic chains on superconductors induced by topological end states hosted at their ends. These magnetic chains have so far been engineered from magnetic atoms . On-surface synthesis of triangulene spin chains has been already realized on Au(111), where fractional edge states have been reported [5]. However, organic reactions are difficult to take place on superconductors due to the high reactivity of most superconducting substrates. Here, we use a proximitized thin film of silver grown ontop of a bulk niobium crystal as our platform for achieving on-surface synthesis of one-dimensional molecular spin chains that contain the S = 1 triangulene unit as the building block. In this work, we report the growth of the silver buffer layer as well as the formation of Ag(111) islands on top of Nb(110) and Nb(100). We show the on-surface synthesis route for the triangulene chains, along with the electronic characterization by means of scanning tunneling microscopy and spectroscopy. The triangulene chains show no magnetic signal on this proxmitized silver surfaces probably due to electronic charge transfer from the metal. However, a clear magnetic fingerprint, manifested as in-gap Yu-shiba-rusinov states, is found in some triangulene units probably because of intrinsic defects in the formation of the chains. These shows that proxmitized silver substrates are an ideal platform to study spin physics of extended pi- conjugated molecular systems.

[1] P. Brydon, S. D. Sarma, H.-Y. Hui, and J. D. Sau, Physical Review B 91, 064505 (2015).
[2] Y. Peng, F. Pientka, L. I. Glazman, and F. Von Oppen, Physical review letters 114, 106801 (2015)
[3] S. Nadj-Perge, I. Drozdov, B. A. Bernevig, and A. Yazdani, Physical Review B 88, 020407 (2013)
[4] S. Nadj-Perge, I.K. Drozdov, J. Li, H. Chen, S. Jeon, J. Seo, A. H. Macdonald, B. A. Bernevig, and A. Yazdani , Science 346, 602-607 (2014)
[5] Mishra, S., Catarina, G., Wu, F. et al. , Nature 598, 287–292 (2021)