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

 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 wavefunctions.  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. 

Participante: Dr. Rolando Valdés Aguilar

Institución:

Lugar: Auditorio ICF

Fecha y hora: Este evento terminó el Jueves, 16 de Junio de 2011