Quantum Geometric Dipole in Collective Excitations
DIPC Seminars
- Speaker
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Herbert Abraham Fertig, Indiana University
- When
-
2022/11/11
13:00 - Place
- Auditorium, Centro de Fisica de Materiales
- Add to calendar
-
iCal
In recent years it has become increasingly appreciated that electrons in
solids possess quantum geometric structure that impact the electronic
properties of the system. Typically, this takes the form of a Berry curvature
which contributes to the electron velocity in its response to external fields.
In this talk we discuss quantum geometric properties of collective modes of
electronic materials, focusing on those that can be described as two-body
excitations. We show that generally such excitations possess their own type
of geometric measure, closely related to an electric dipole moment, which we
call the quantum geometric dipole (QGD). We will focus on two examples of
this: excitons in semiconducting systems, and plasmons in two-dimensional
metals. We show that for excitons, a non-zero QGD appears when there is no
effective Lorentz invariance in the system, even at long wavelengths, and that
its presence leads to a perpendicular exciton drift in an electric field. For
the case of plasmons, we consider the impact of the QGD on scattering from a
circularly symmetric potential, showing that the QGD necessarily gives rise to
non-reciprocal behavior. In general the presence of a non-vanishing QGD
impacts the dynamics of these collective modes, and we discuss some
implications for experiment.
Hosts: Fernando de Juan