Forum DQMP – Sara Riccò (group of Prof. Baumberger)/ Ignacio Gutiérrez-Lezama (group of Prof. Morpurgo)

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Date(s) - 21/11/2017
3 h 26 min - 14 h 30 min

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DQMP, Ecole de Physique, 24 quai Ernest-Ansermet, CH-1211 Genève 4, http://dqmp.unige.ch
Forum DQMP
Doping evolution of the multi-band Mott insulator Ca2RuO4
Sara Riccò (group of Prof. Baumberger)
High temperature superconductivity, colossal magneto-resistance and many other intriguing phenomena
in correlated electron physics arise in doped Mott insulators. However, to date the evolution of the microscopic
electronic structure from the locked Mott state towards itinerant states that underlies these phenomena
has only been characterized in a handful of systems, most notably some of the cuprate high-Tc
superconductors, layered manganites and, very recently, iridates. Here we present the first angle-resolved
photoemission (ARPES) study of electron doped Ca2RuO4, which has been investigated intensely
as a model system of a multi-band Mott transition. Using a series of La- and Pr-doped Ca2RuO4 single
crystals grown by the floating zone technique we are able to separate the metal insulator transition from
the structural phase transition and study the genuinely filling induced metallic state. Our results show that
some key-properties of doped Mott insulators, such as the momentum dependent pseudogap seen in
cuprates and iridates, are not realized in multi-band systems.
The path to encapsulated monolayer WTe2
Ignacio Gutiérrez-Lezama (group of Prof. Morpurgo)
The possibility to mechanically exfoliate van-der-Waals bonded crystals, such as transition metal
dichalcogenides (TMDs) and graphite, has resulted in the widespread study of the thickness evolution of
their electronic structure and the observation of novel physical phenomena hosted by two (2D)-dimensional
crystals. Among this plethora of materials, semimetallic WTe2 has received increasing attention
due to its record high no-saturating magnetoresistance and the theoretical predictions of it being a type-II
Weyl semimetal and its strained monolayer a 2D topological insulator. Unfortunately, monolayer WTe2 oxidizes
in air hindering the observation of its intrinsic electronic properties. In this talk we will mainly discuss
the technique recently developed in our group to encapsulate air sensitive materials in an inert atmosphere,
which we have successfully employed to realize working van der Waals heterostuctures. We
will also discuss our first transport measurements on monolayer WTe2, which show the existence of a
band gap of about 10 meV and that the conductance inside the gap is just below the quantum of conductance,
hinting towards the existence of edge states.
Forum Committee : C.Lichtensteiger, A.Tamai, N.Ubrig (13.03.2017)
Tuesday, March 21st 2017 – 13h00
Auditoire Stückelberg
Ecole de physique
Coffee and tea will be available from
12h50 at the entrance of the Auditoire

 

 

 

 

 

 

 

 

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