GHN-colloquium with Prof. Hélène Bouchiat

Summary

The GHN-Colloquium talk series features the female scientists of the Grete-Hermann-Network (GHN)—a newly founded international network of female researchers in condensed matter physics and neighboring research areas. Distinguished female researchers are invited to give a lecture on their research and current projects, as well as about their career paths, to inspire young female scientists in particular, and to exchange ideas. After the official talk there will be an internal GHN-networking event.

 

On 06 July 2021 we are happy to welcome Prof. Hélène Bouchiat from Universite de Paris-Saclay who will give an online scientific talk about Revealing the topological nature of transport at mesoscopic scales with quantum interferences.

 

 

 

 

Talk abstract

 

 

A mesoscopic conductor is characterized by its size smaller than the phase coherence length of electronic wave-functions (typically one micrometer at low temperature). Mesoscopic electronic transport depends strongly on the nature of interferences between these wave functions determined by the scattering disorder potential which tends to localize electronic states at low dimension. Moreover, these interferences can be modulated by a magnetic flux through the Aharonov-Bohm effect giving rise to orbital persistent currents in ring geometries. These interferences also determine the Josephson supercurrent of a mesoscopic normal conductor when connected to superconducting electrodes.

 

We show that these basic fundamental properties of mesoscopic quantum interferences can be used to reveal the existence and the physical location of 1d protected states in topological insulators. This method is illustrated in the case of crystalline bismuth nanowires which were found to belong to a class of newly discovered higher order topological insulators with helical ballistic hinge states coexisting with trivial bulk and surface diffusive states. In particular we discuss SQUID like periodic magnetic oscillations observed in Bi based Josephson junctions.

 

 

 

 

About Hélène Bouchiat

 

 

Hélène Bouchiat is a condensed matter physicist and director of research in the French National Centre for Scientific Research (CNRS), associated with the Laboratoire de Physique des Solides at Paris-Sud University. She received her PhD in 1986 at Paris-Sud University. As a postdoctoral researcher Hélène Bouchiat stayed 18 months at Bell Labs (USA). Her research interests are specialized in mesoscopic physics and nanoscience. Topics in her research include supercurrents, persistent currents, graphene, carbon nanotubes, and bismuth-based topological insulators.

 

Bouchiat is a member of the French Academy of Sciences, elected in 2010. The academy also gave her their Anatole and Suzanne Abragam Prize in 1994, and their Jaffé Prize in 1998. she was awarded with the CNRS bronze and silver medals in 1987 and 2007 respectively.