Mirror-symmetric Magneto-optical Kerr Rotation using Visible Light in [(GeTe)2(Sb2Te3)1]n Topological Superlattices

Abstract

Interfacial phase change memory (iPCM), that has a structure of a superlattice made of alternating atomically thin GeTe and Sb2Te3 layers, has recently attracted attention not only due to its superior performance compared to the alloy of the same average composition in terms of energy consumption but also due to its strong response to an external magnetic field (giant magnetoresistance) that has been speculated to arise from switching between topological insulator (RESET) and normal insulator (SET) phases. Here we report magneto-optical Kerr rotation loops in the visible range, that have mirror symmetric resonances with respect to the magnetic field polarity at temperatures above 380 K when the material is in the SET phase that has Kramers-pairs in spin-split bands. We further found that this threshold temperature may be controlled if the sample was cooled in a magnetic field. The observed results open new possibilities for use of iPCM beyond phase-change memory applications.

Modeling of switching mechanism in GeSbTe chalcogenide superlattices

“…There have been a number of experimental demonstrations of the CSL memory567891011, but the switching mechanism is so far not fully defined at an atomic level. There have been several suggestions to explain how the atoms are manipulated, including charge injection12, electric field613, magnetic field6, thermal activation7 and polarization dependent optical control14.…”

“…There have been several suggestions to explain how the atoms are manipulated, including charge injection12, electric field613, magnetic field6, thermal activation7 and polarization dependent optical control14. However, the atomic structures of the low resistance state (LRS) and high resistance states (HRS) are still not fully agreed by different groups, so the atomic mechanism needs further definition.…”

“…Referring to Fig. 1, Model 1 proposes a transition from a Ferro LRS to an Inverted-Petrov structure HRS7815. Model 2 proposes a transition between a Petrov LRS and an Inverted-Petrov HRS111216.…”

A two-step process for growth of highly oriented Sb2Te3 using sputtering

“…11 Furthermore, several superlattice structures including GeTe/Sb 2 Te 3 have been theoretically predicted to exhibit unusual properties forming topological insulators or Dirac semimetals, leading to the experimental confirmation of unusual magnetic properties despite the lack of magnetic elements. [12][13][14][15] The most widely used techniques to fabricate 2D chalcogenides are exfoliation from a bulk single crystal, chemical vapor deposition (CVD), and molecular beam epitaxy (MBE). [16][17][18][19][20][21] However, the area of films that can be fabricated by exfoliation is limited and sample sizes are not uniform.…”

Investigation of switching region in superlattice phase change memories

“…These reports suggested that the switching was due to vertical displacements of Ge atoms at the interface of GeTe layers and Sb 2 Te 3 layers in the superlattice. The driving force of the Ge displacements has been attributed to charge injections, 9 electric field, 10 thermal activation, 11 and stresses in the superlattice films. 12,13 However, we need to clarify whether these displacements occurred in all interfaces in the superlattice, in a part of the interfaces, or in other regions.…”