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System eletron-hole two-dimensional and three-dimensional topological insulator quantum wells HgTe


Among the many systems two-dimensional (2D) conducted until now, the only known electron-hole system was conducted in heterojunctions of InAs / GaSb, this system 2D electrons and holes exist simultaneously, because the conduction band of InAs is the opposite valence band of the GaSb [1-4]. The system displays several properties of magneto transport associated with current carriers with opposite signs, in this system, the electrons and holes in 2D although located in a close proximity, yet remain separated by the barrier of the heterojunction, so the electrons and holes are mainly located in the InAs and GaSb, respectively.We propose the study of electron-hole system in two-dimensional semiconductor structures of HGTE / CdTe produced at the Institute of Semiconductor Physics, Novosibirskt. These systems is mainly expected the formation of so-called exciton insulator suggested initially by N. Mott [5]. The concept of the exciton insulator can be explained as follows: in a semimetal with low densities which electrons and holes to the Coulomb interaction is no longer reduced by shield and can result in the formation of electron-hole bound states, the fact is that the exciton is a neutral particle, and the system under these conditions becomes an insulator.Wide quantum wells of CdHgTe / HGTE / CdHgTe, are also related to the three-dimensional topological insulator (3D). It was provided that due to the reversal of the band also has HGTE 3D shaped surface states of the Dirac cone [6-9], but since the material is semi-metallic, this state is always coupled with the bulk states. With the applied voltage opens a gap between heavy hole and light-hole heavy, so HGTE 3D stressed seen a 3D topological insulator. It was envisaged that the second harmonic generation is a promising tool for the study of spectroscopy of topological surfaces and buried interfaces.The study of two-dimensional electron-hole system and 3D topological insulator in semiconductor structures HGTE / CdTe and collaborations between IFUSP and Institute of Physics of Semiconductors have started in 2007 with proposals to FAPESP (aid researchers visitors: 2007/07953-2 , 2008/09212-2, 2010/10097-3). Several studies have been published (among them two PRL) involving the use of these samples [Ref.9-12], and several papers that are in preparation.Some benefits of this project are: the evolution of knowledge of the physics of nano-structured systems, the development of techniques for characterizing quantum wells HGTE high quality and application of this knowledge as possible (or its consequences) in future electronic devices and bipolar spintronics. (AU)