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Topological Insulators

Topological insulators (TIs) are a new quantum state of matter characterized by being insulating in the bulk, while hosting metallic state at the surface. The surface state disperses linearly across the bulk gap connecting the valence and conduction band (see figure below). It obeys the Dirac-Weyl equation like the well-known graphene, and more importantly it shows a single helical spin component. This makes TIs ideals candidate for novel spintronics devices, based on the capability to use electronic current to carry magnetic information, without spin decoherence effects.

Tr-ARPES offers a tool to investigate the coupling between light and the Dirac surface particle in TIs, in the perspective to manipulate their spin states via optical excitation. Moreover, through out-of-equilibrium spectroscopies we can estimate the roles played in the electronic relaxation by various contributions, such as electron-electron scattering, electron-phonon scattering, electron diffusion and impact ionization scattering processes. The study of these physical quantities is of mandatory importance because they ultimately define the electric transport property of TIs.

Left: Energy diagram of a typical topological insulator
Right: Experimental band structure of the surface spin helical Dirac particle in Sb2Te3 as directly imagined after the optical excitation

For further information contact:
Michele Zacchigna
Federico Cilento

Last Updated on Thursday, 23 February 2017 13:08