Materials Screening for Anderson Localization in Disordered Chalcogenides

Riccardo Mazzarello^1*, Yazhi Xu^1,2, Xudong Wang², Wei Zhang²

¹ Institute for Theoretical Solid State Physics and JARA, RWTH Aachen, 52056 Aachen, Germany

² Center for Advancing Materials Performance from the Nanoscale and Materials Studio for Neuro-inspired Computing, Xi’an Jiaotong University, Xi’an 710049, China

ABSTRACT: Disorder-induced Anderson localization and metal-insulator transition have been a central topic in both condensed matter physics and materials science in the past 60 years. Recently, Anderson localization has been observed in Ge-Sb-Te alloys forming a metastable rocksalt-like phase with high concentration of atomic vacancies (~10%). This phase is obtained by rapid crystallization from the amorphous state in phase-change memory devices and, thus, is of considerable technological importance. For demanding applications in phase-change electronics or photonics, it is crucial to have a pool of materials with tunable electronic and transport properties, including band gap size and electron localization length. Therefore, it is of pressing need to carry out a systematic search for compounds exhibiting Anderson localization features.

Here, we demonstrate by ab initio simulations and transport experiments that the parent compound of Ge-Sb-Te alloys –Sb₂Te₃– is also an Anderson insulator in the rocksalt-like structure, and elucidate why such disordered crystalline phase can form, extending the exploration of Anderson insulators to binary chalcogenides. We then carry out a systematic ab initio computational screening over all binary and ternary chalcogenides with V₂VI₃ and IVV₂VI₄ compositions and identify 47 (meta-)stable rocksalt-type compounds that can sustain a high degree of disorder. Our large-scale electronic structure calculations reveal that most of these disordered chalcogenide crystals are Anderson insulators, with localization length of ~0.5–2 nm and band gap size of ~0.2–1.8 eV. Moreover, we obtain an in-depth understanding of the critical factors that affect the stability of the rocksalt structure, namely, sp³ mixing and atomic radius ratio, and distinguish (meta-)stable compounds from unstable ones in a rationalized materials map. We show that this map can be employed to predict the properties of thousands more compositions with varying localization length and band gap size so as to expand the application range of phase-change materials.

Keywords：phase-change materials; Anderson insulators; metal-insulator transitions