CMSP Seminar Series @ICTP Stasi Room: S. DE PALO Thursday 9 November

[CM Section]

ICTP Seminar Series in Condensed Matter and Statistical Physics
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Thursday 9 November at 11:30 a.m.

Luigi Stasi Seminar Room, first floor, ICTP Leonardo building
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Speaker:
Stefania DE PALO (CNR-IOM and University of Trieste, Italy)

Title:
Valley Degeneracy Effects in Two-Dimensional Gases

Abstract:
The electronic structure of many devices where the two-dimensional gases
are engineered can have degenerate valleys to be occupied by charge 
carriers.
This feature for long has been seen as a drawback, but more recently,
also owing to the discovery of graphene and monolayer group-VI transition
metal dichalcogenides, it has been recognized as an opportunity to have an
additional degree of freedom to manipulate the electrons beside the 
charge and
the spin, leading to the so-called valleytronics. The valley degeneracy, 
that in
a minimal description can be seen as an additional spin, has large 
impact on
correlations in these systems and can enrich their phase diagram in general.

In this talk I will discuss how this additional degree of freedom 
affects two different
systems.How valley polarization changes the magnetic response in AlAs 
quantum
well once we take into account the mass anisotropy proper to this system 
and how
results on spin-susceptibility, based on Quantum Monte Carlo 
simulations, compare
with experimental findings.The other aspect that will be addressed is 
how the phase
diagram of a symmetric electron-hole bilayer is modified once there is 
in-plane two-
fold valley degeneracy.Results for this simple model can be relevant for 
the recent
proposal to search for indirectexcitons condensation in coupled graphene 
bilayers
that, on a wide density range, have a quadratic energy dispersion.