Abstract：

　　In this talk, I will presentour recent experimental observations of the large-scale mesoscopic transport innanostructured graphene, and tunnelling spectroscopy in gate-inducedsuperconductivity in MoS_2.

　　I will first talkabout the observation of Anderson localization in two dimensions through samplesize scaling on nanostructured graphene. The localization length is observed toincrease with applied magnetic field, in accurate agreement with the theoreticalprediction. The large-scale mesoscopic transport is manifest as a parallelconduction channel to 2D variable range hopping, with a Coulomb quasigap aroundthe Fermi level, which leads to an observed dephasing length of 10 μm.

　　Then the study of gate-inducedsuperconductivity in MoS₂ by performing tunnelling spectroscopythrough the van der Waals heterostructures will be presented. The ability togate-induce superconductivity by electrostatic charge accumulation is a recentbreakthrough in physics and nano-electronics, but experiments on gate-inducedsuperconductors have been largely confined to resistance measurements, whichprovide very limited information about the superconducting state. We exploregate-induced superconductivity in MoS₂ by performing tunnellingspectroscopy to determine the energy-dependent density of states (DOS) fordifferent levels of electron density n.Our measurements reveal the presence ofa DOS that vanishes linearly with energy, whose explanation requires going beyonda conventional, purely phonon-driven BCS mechanism.  The bandstructure study of Transition metaldichalcogenides (TMDs) will also be discussed. By combining the in-planetransport, tunnelling spectroscopy and carrier density measurement, we are ableto determine the valley occupation in TMDs, which is meaningful forunderstanding the microscopic mechanism of the gate-induced superconductivity.

Biosketch：

　　Dr. Haijing Zhang received herBachelor degree from Nanjing University in 2009 and got her Ph.D in physicsfrom Hong Kong University of Science and Technology (HKUST) in 2014 under thesupervision of Prof. Ping Sheng. From September 2014 to September 2016, sheworked in the physics department of HKUST as a Post-doctoral Fellow. Startingfrom October 2016, she joined Prof. Alberto F. Morpurgo’s group as aPost-doctoral Fellow in the Department of Quantum Matter Physics at Universityof Geveva, Switzerland. Her research interests mainly focus on quantum andmesoscopic transport properties on nanostructured 2D materials and 2Dgate-induced superconductivity.