PhD Thesis Defense | Cristina Mier González

Atomic and molecular structures on a superconducting surface

May 4, 10:00

CFM Auditorium

Candidate: Cristina Mier González

Supervisors:  Nicolás Lorente Palacios & Deung-Jang Choi

This Ph. D. thesis studies the physical properties of magnetic impurities and spin chains on s-wave superconductors. This is an important field of research that has acquired particular importance in recent years thanks to technological advances in the study of superconducting surfaces at the atomic level.

Within the last decade, an important effort in creating and measuring the properties of spin chains on superconductors has been led by the search of Majorana bound states. These emergent quasi-particles have been proposed as building blocks for default-free quantum computing protocols.

The thesis focuses on two superconductors (Pb and β-Bi2Pd). The research includes both experimental and theoretical studies, with a focus on understanding the conditions under which Majorana bound states can be found. The thesis also highligths the use of scanning tunneling microscopy (STM) as a tool for studying magnetic atoms and molecules on superconducting surfaces.

Figure 1: (a) Geometry of the modelled system: s-wave bulk superconductor (blue balls) with a ferromagnetically ordered spin chain (orange balls) on its surface. (b) Upper panel: experimental STM measurements of Cr atomic chains deposited on the superconductor β-Bi2Pd. Lower panel: Calculations are able to reproduce the experimental results from the upper panel.