Abstract
:
In this talk, I will present
our recent experimental observations of the large-scale mesoscopic transport in
nanostructured graphene, and tunnelling spectroscopy in gate-induced
superconductivity in MoS2.
I will first talk
about the observation of Anderson localization in two dimensions through sample
size scaling on nanostructured graphene. The localization length is observed to
increase with applied magnetic field, in accurate agreement with the theoretical
prediction. The large-scale mesoscopic transport is manifest as a parallel
conduction channel to 2D variable range hopping, with a Coulomb quasigap around
the Fermi level, which leads to an observed dephasing length of 10 μm.
Then the study of gate-induced
superconductivity in MoS2 by performing tunnelling spectroscopy
through the van der Waals heterostructures will be presented. The ability to
gate-induce superconductivity by electrostatic charge accumulation is a recent
breakthrough in physics and nano-electronics, but experiments on gate-induced
superconductors have been largely confined to resistance measurements, which
provide very limited information about the superconducting state. We explore
gate-induced superconductivity in MoS2 by performing tunnelling
spectroscopy to determine the energy-dependent density of states (DOS) for
different levels of electron density n.
Our measurements reveal the presence of
a DOS that vanishes linearly with energy, whose explanation requires going beyond
a conventional, purely phonon-driven BCS mechanism. The bandstructure study of Transition metal
dichalcogenides (TMDs) will also be discussed. By combining the in-plane
transport, tunnelling spectroscopy and carrier density measurement, we are able
to determine the valley occupation in TMDs, which is meaningful for
understanding the microscopic mechanism of the gate-induced superconductivity.
Biosketch
:
Dr. Haijing Zhang received her
Bachelor degree from Nanjing University in 2009 and got her Ph.D in physics
from Hong Kong University of Science and Technology (HKUST) in 2014 under the
supervision of Prof. Ping Sheng. From September 2014 to September 2016, she
worked in the physics department of HKUST as a Post-doctoral Fellow. Starting
from October 2016, she joined Prof. Alberto F. Morpurgo’s group as a
Post-doctoral Fellow in the Department of Quantum Matter Physics at University
of Geveva, Switzerland. Her research interests mainly focus on quantum and
mesoscopic transport properties on nanostructured 2D materials and 2D
gate-induced superconductivity.