Sommaire:

A time-reversal invariant topological insulator in two dimensions, also known as a quantum spin Hall insulator (QSHI) is a new state of matter characterized by an insulating bulk and spin-polarized gapless helical states at the sample edges. So far, evidence for the helical edge mode in QSHI, particularly quantized transport, has been limited to two semiconductor systems – inverted HgTe/CdHgTe quantum wells (QWs) and broken-gap InAs/GaSb QW bilayers. In my talk, I review recent theoretical and experimental results on single and double HgTe QWs, obtained in our group in Montpellier. In the first part, I will focus on phase transitions in single HgTe QWs induced by temperature and present the picture of the edge states in QSHI phase beyond the Bernevig-Hughes-Zhang model. In the second part, I report theoretical study of phase transitions in double HgTe QWs consisting of two HgTe layers separated by tunneling CdHgTe barrier. Particularly, I show an existence of specific “bilayer-graphene” metal and trivial insulator phases, arising in the inverted double HgTe QWs. Finally, motivated by recent observation of quantum spin Hall effect at temperatures up 100 K in 1T′-WTe2 monolayers with a band-gap of 45 meV (Science 359, 76 (2018)), I will briefly discuss a possibility of realization of high-temperature QSHI in multi-layer InAs/GaSb QWs with temperature stable band gap.

Pour plus d'informations, merci de contacter Teppe F.