Magneto optical Kerr rotation of [(GeTe)2(Sb2Te3)1]n superlattice

Since the invention of interfacial phase change memory (iPCM), which has recently been newly named topological switching random access memory, TRAM or TSRAM, the switching energy in phase change memory (PCM) has greatly been suppressed less than 1/20 [1-3]. In addition, soon after the invention, it was reported that iPCM has an electrically-induced giant magneto-resistance more than 2,000% at room temperature despite being non-magnetic if it were the alloy [4]. iPCM, on the other hand, has recently been studied as a topological insulator [5]; Sb₂Te₃ is a topological insulator (TI) while GeTe is a normal insulator (NI) with a narrow band gap [6]. Since in TI both time-reversal symmetry and spatial inversion symmetry are preserved, TI is usually non-magnetic. However, breaking the symmetries may emerge spin-related properties. Shi et al. reported different spin currents localized at sample edges using a Kerr rotation method [7]. Furthermore, a giant Kerr rotation has theoretically been predicted in TI [8]. Therefore, it is very interesting to confirm if iPCM changes the Kerr-rotation by the breaking of the time reversal symmetry and spatial inversion symmetry.