Pseudogap Feature in the Electronic Density of States of Weakly Localized Ge₂Sb₂Te₅ Samples

Phase change materials such as Ge₂Sb₂Te₅ (GST) are known to exhibit electronic localization phenomena [1,2]. We have studied bulk single crystals of GST and Ge₂Sb₂Te_5(1−x) Se_5x(GSST) using a comprehensive approach that incorporates angle-resolved photoemission spectroscopy (ARPES) and magnetic field-dependent electronic transport measurements. We observe that as x, i.e., the amount of Se substitution of Te, increases, a transition occurs from a bad metal to a weakly localized system for x ≥ x_c~ 0.6. The positive magnetoresistance trend in samples with x ≥ x_c indicates the presence of strong spin-orbit coupling, while the temperature dependence of both the resistance and the extracted phase coherence length implies strong electronic interactions. At the same time, ARPES measurements show finite electronic density of states (DOS) for all values of x, which is expected in the case of weak localization [3]. However, above x_c, the DOS is partially suppressed (pseudogapped) at the chemical potential, and this suppression is significantly broader than what one would expect from e.g. [3]. Our results establish that GSST can act as a model system for a tunable disordered metal with appreciable electronic interactions, where the interplay between electronic correlations and disorder can manifest itself via an emergent pseudogap behavior in the DOS.



[1] N. P. Breznay, et. al., Phys. Rev. B 86, 205302 (2012).

[2] J.-J. Wang, et al., Materials 10, 8 (2017).

[3] B. L. Altshuler et al, Elsevier, 1985, pp. 1–153.