## Supercurrents at finite magnetic field in InSb nanowires

报告人: Dr. Vincent Mourik ( Niels Stensen Fellow at the University of New South Wales, Australia)

报告时间: 2016年8月30日 15:00

报告地点: 理科楼C109

**摘要：**In the first half of my seminar, I will present an ongoing effort from my PhD research:

**Supercurrents at finite magnetic field in InSb nanowires**

The engineering of topological superconductors and the observation and control of their non-abelian quasiparticles is a dominant effort in condensed matter physics, both out of fundamental interest and for their potential application in topological quantum computing. A one-dimensional semiconducting nanowire with strong spin-orbit interaction that is proximity coupled to a standard s-wave superconductor is a particularly attractive implementation of a topological superconductor due to its relative ease of fabrication. One of the prime signatures of the existence of Majorana fermions in such a structure would be the observation of the 4pi Josephson effect. Furthermore, several proposed braiding schemes heavily rely on good quality Josephson junctions working at considerable magnetic field strengths. I will present the typical behavior we found of the supercurrent in such nanowires, along with our current insights in the physical interpretation of our observations.

In the second half of my presentation, I want to shift focus to my new post-doctoral research topic:

**The emergence of chaos in a single spin in silicon**

Classical conservative systems usually exhibit rapid dispersion of initial conditions – chaos – while the quantum version of the same systems exhibit quasi-periodicity, localization and tunneling through classically forbidden regions of phase space. How to reconcile this strikingly different behavior has been the topic of much theoretical debate, but little experimental proof, and none whatsoever on a single quantum system observed in real time. My project aims at achieving the first real-time experimental observation of the quantum dynamics of a single classically chaotic system – a periodically-driven non-linear top. This I want to achieve by combining the existing infrastructure for donor based spin qubit in silicon in the group of Prof. Morello at the University of New South Wales with a new type of donor, having a large nuclear spin and a non-linearity due to nuclear quadrupole interaction. I will outline the upcoming experiments and discuss their theoretical modelling.

**Bio: **Vincent Mourik is an experimental condensed matter and quantum physicist. He studied at Delft University of Technology, the Netherlands, from which he graduated in 2010. He continued doing his PhD research at the same university in the group of Prof. Leo Kouwenhoven, at the Kavli Institute of Nanoscience and the QuTech institute. The topic of his PhD research was to engineer and detect Majorana fermions in hybrid superconductor-semiconducting nanowire structures [1]. The main result of his PhD research, the observation of the first signatures of Majorana fermions, got published in Science in 2012 [2] and garnered a wide attention not only in the physics community, but also in popular press. Starting December 2015, Vincent is conducting his post-doctoral research as a Niels Stensen Fellow in the group of Prof. Andrea Morello at the University of New South Wales, Australia. His focus is on fully controlling for the first time a single, higher nuclear spin donor in silicon. The goal is to study and understand the emergence of classical dynamics present in the macroscopic world from an inherently quantum dynamical microscopic world, a research field known as 'quantum chaos'.

[1] K. Zuo & V. Mourik, *Signatures of Majorana fermions in hybrid superconducting-semiconducting nanowire devices*, PhD thesis, 2016. Download viahttp://repository.tudelft.nl/view/ir/uuid%3A3fd0aed5-000c-4e50-a772-269436637fc4/

[2] V. Mourik, K. Zuo et al. *Signatures of Majorana fermions in hybrid superconducting-semiconducting nanowire devices*, Science 2012, DOI: 10.1126/science.1222360