Séminaire de groupe
Graphene Induced Topological Insulator (Topological order and Superconductivity) 
Cyril Petitjean 
jeudi 17 janvier 2013 , 14h00 
Salle de séminaire du groupe de Physique Statistique 
Twodimensional topological insulators are commonly referred to as quantum spinHall (QSH) states [1]. Contrary to the threedimensional topological insulators that have been found to abound in nature, the twodimensional are rather limited. However recently a spinorbit induced QSH phase has been proposed [2]. The key ingredient is the use of indium adatoms deposited on the surface of graphene thats should turn the latter into a QSH insulator characterized by a sizable gap. This artificial QSH system present strong potentials applications for thermopower [3] or spintronics [4] devices. One interesting fact about indiums is that the latter becomes superconductor at low enough temperature, Therefore the graphene+indium artificial QSH system becomes a promising candidate to study the competition between induced superconductivity and the spinorbit coupling [5]. In this talk, we will first give a short introduction on the twodimensional topological insulators and the related artificial QSH system. We will then present how such setup can naturally provides a spinpolarized current switch [4]. We finally turn on the superconducting order and spinorbit competition. We show that starting form a general superconducing plaquette interaction, the latter can be reduced to a simpler effective model. This permit us to determine the first preliminary phase diagram [5]. <br> [1] C. L. Kane and E. J. Mele, Phys. Rev. Lett. 95, 226801 (2005). <br> [2] C.Weeks, J. Hu, J. Alicea, M. Franz, and R. Wu, Phys. Rev. X 1, 021001 (2011) <br> [3] O. Shevtsov, P. Carmier, C. Groth, X. Waintal, and D. Carpentier, Phys. Rev. B 85, 245441 (2012). <br> [4] O. Shevtsov, P. Carmier, C. Petitjean,C. Groth, X. Waintal, and D. Carpentier, Phys. Rev. X 2, 031004 (2012). <br>[5] C. Petitjean, E. Orignac and D. Carpentier in preparation 
