Fractionalization of Integer Quantum Hall edge state

Dr Biswajit Karmakar, Associate Professor, Saha Institute of Nuclear Physics, India

Integer quantum Hall (IQH) states which are well understood in terms of non-interacting electrons are expected to have dissipation-less edge states transport from protected integer charge modes with conductance of /h. However, in strong Coulomb interaction regime, nucleation of dominant fractional quantum Hall (FQH) gaps at filling ν  = 1/3 and 2/3 gives rise to incompressible strips around the smooth boundary of IQH system. As a consequence, edge states of IQH system become fractionalized into three downstream charge modes of conductance /3h each. In this talk I shall present the edge state fractionalization at long mesa boundary of ν = 1 IQH states in high mobility 2DEG. We experimentally demonstrate that ν = 1 IQH edge state is composed of three robust downstream fractional 1/3 charge modes. Equilibration between the modes can be controlled by tuning the magnetic field within the extent of ν = 1 IQH plateau. In our experiment, we could unveil the equilibration properties of the modes and this finding is linked to formation of the two set of fractional conductance plateaus of values 1/9, 2/9, 4/9 and 1/6, 1/3, 2/3 at the two ends of ν = 1 IQH plateau under selective excitation and detection of the fractionalized1/3 modes.

New physics of old graphite

Dr Artem Mishchenko,  University of Manchester

Graphite fascinated researchers for decades, but only recently experimental and theoretical breakthroughs allowed to study this old material in the purest form which led to plenty of discoveries. I will present our recent experimental results to catalyse further research of nontrivial physics in this elementary semimetal. Manchester

Unravelling properties of Brown-Zak fermions at ultra-low temperatures

 Julien Barrier, University of Manchester

In quantising magnetic fields, graphene superlattices exhibit a complex fractal spectrum often referred to as the Hofstadter butterfly. It can be viewed as a collection of Landau levels that arise from quantization of Brown-Zak minibands recurring at rational (p/q) fractions of the magnetic flux quantum per superlattice unit cell. I will show that, in graphene-on-boron-nitride superlattices, Brown-Zak fermions can exhibit mobilities above 10⁶ cm² V^-1 s^-1 and the mean free path exceeding several micrometres. High resolution measurements and high quality devices allow us to show that Brown-Zak minibands are 4q times degenerate and all the degeneracies (spin, valley and mini-valley) can be lifted by exchange interactions below 1 K. Moreover, in some parts of the Hofstadter spectrum, Landau levels exhibit nonlinear and staircase-like features that cannot be explained within a single-particle picture. 

Quantum computing and qubit scale-up applications with Proteox

James Robinson, Product Manager, Oxford Instruments

This webinar provides an overview of the new Proteox dilution refrigerator from Oxford Instruments, highlighting the key features and suitability for many quantum computing and qubit scale-up applications. The Proteox system is an essential tool for low temperature researchers, providing advanced research capability. It enables a step change in Cryofree system modularity, designed for enhanced adaptability, reliability and increased experimental capacity. If you are dealing with low temperature experiments, don’t miss this webinar.