Tunable Electronic Interactions and Weak Antilocalization in Bulk Ge$_2$Sb$_2$Te$_{5-5x}$Se$_{5x}$ Phase Change Materials

Phase change materials (PCMs) are well-known for their reversible and rapid switching between crystalline and amorphous phases through thermal excitations mediated by strong electrical or laser pulses. This crystal-to-amorphous transition is accompanied by a remarkable contrast in optical and electronic properties, making PCMs useful in nonvolatile data storage applications. Here, we combine electrical transport and angle resolved photoemission spectroscopy (ARPES) measurements to study the electronic structure of bulk Ge$_2$Sb$_2$Te$_{5-5x}$Se$_{5x}$ (GSST) for $0\le x \le 0.8$, where $x$ represents the amount of Se substituting Te in Ge$_2$Sb$_2$Te$_5$ (GST)-- a prototypical PCM. The single-particle density of states (SDOS) derived from the integrated ARPES data displays metallic behavior for all $x$, as evidenced by the presence of a finite density of states in the vicinity of the chemical potential. Transport measurements also display clear signatures of metallic transport, consistent with the SDOS data. The temperature dependence of the resistance indicates the onset of moderate electron-electron Coulomb interaction effects at low temperatures for $x\geq 0.6$. At the same time, the magnetoresistance data shows signatures of weak antilocalization for $x\geq 0.6$. An analysis on the temperature dependence of the phase coherence length suggests that electron dephasing is primarily due to inelastic electron-electron scattering. We find that these effects are enhanced with increasing $x$, portraying GSST as a novel PCM where electronic interactions can be tuned via chemical doping.