Seminario de Estudiantes

["Rafael Verduzco" <rvv@xxxxxxx>]

Estimados todos:

Este jueves el Seminario de Estudiantes del Instituto cede su espacio para
la plática que dará el Dr. Rolando Valdés Aguilar, titulada:

"THz response and colossal magneto-electric effect in the topological
insulator Bi2Se3"

Invitamos a toda la comunidad a asistir a este evento.  Encuentren al final
de este correo el resumen de la plática.
Nos vemos en el Auditorio del Instituto a las 5:30 pm

Saludos cordiales,

Jorge Pérez y Rafael Verduzco.


Resumen:

Ordered states of matter are typically categorized by their broken
symmetries. With the ordering of spins in a ferromagnet or the freezing of a
liquid into a  solid, the loss of symmetry distinguishes the ordered state
from the disordered one.  In contrast, topological states are distinguished
by specific topological properties that are encoded in their quantum
mechanical wave functions.  Frequently, a consequence of these properties is
that there are robust  topologically protected states on their boundaries.
The edge states of the quantum Hall effect (QHE) are the classic example.
In the last few years, it was realized that another class of such
topological matter may exist in 3D band insulators with large spin-orbit.
These so-called topological insulators are predicted to host robust surface
states, which exhibit a number of interesting properties including spin
helicity, immunity to back-scattering, and weak anti-localization.  Here we
report the observation of an unprecedentedly large rotation of up to 65° of
the polarization plane of linearly polarized light reflected (Kerr rotation)
from thin films of topological insulator Bi2Se3 in magnetic fields, which is
due almost entirely to the surface states.  Our results are evidence for the
intrinsic  response of the topologically protected surface states and
provide a benchmark for the magneto-electric effect predicted for these
materials.