Lecturer: Dr. Jonathan Ruhman
Affiliation: Department of Condensed-matter
Physics, Weizmann institute of Science
Abstract:
Measurements performed on the two-
dimensional metallic interface between
LaAlO3 and SrTiO3 indicate that a
magnetic transition occurs when the
density of conduction electrons is tuned in
the presence of a magnetic field [1, 2]. For
example, magneto-transport
measurements find that the resistance
drops sharply exactly where an
anomalous Hall effect develops and the
resistivity becomes anisotropic. The main
questions I deal with in this talk are:
What is the nature of these phases? and
why does the transition between them
depend on the density of conduction
electrons?
To answer these questions I construct a
minimal model consisting of two essential
ingredients: a conduction band
Hamiltonian describing the metallic states
and localized magnetic moments which
reside near the interface. I show that the
magnetic transition observed in
experiment can be explained in terms of a
transition between a state where the
moments are Kondo screened and their
magnetization is suppressed, and a state
where the Kondo screening breaks down
and the moments polarize along the
magnetic field. This model allows me to
construct a global phase diagram that
unifies a variety of experiments and
theoretical models.
[1] Joshua et. al. PNAS 9633 110 (2013)
[2] Bi et. al. Nature Communications 5,
5019 (2014)