Localization Phenomena in Disordered Tantalum Films

TL;DR

This study investigates how disorder in tantalum films leads to charge localization and electronic structure changes, using transport and spectroscopic techniques to understand the underlying physics of disordered metals.

Contribution

It provides new insights into the relationship between disorder, charge localization, and electronic band structure reconstruction in highly disordered tantalum films.

Findings

Increased disorder correlates with decreased Drude response.

Charge localization is associated with changes in high-energy Lorentz bands.

Electronic correlations and many-body effects are key to understanding localization.

Abstract

Using dc transport and wide-band spectroscopic ellipsometry techniques we study localization phenomena in highly disordered metallic \beta-Ta films grown by rf sputtering deposition. The dc transport study implies non-metallic behavior (dr/dT<0), with negative temperature coefficient of resistivity (TCR). We found that as the absolute TCR value increased, specifying an elevated degree of disorder, the free charge carrier Drude response decreases, indicating the enhanced charge carrier localization. Moreover, we found that the pronounced changes occur at the extended spectral range, involving not only the Drude resonance, but also the higher-energy Lorentz bands, in evidence of the attendant electronic correlations. We propose that the charge carrier localization, or delocalization, is accompanied by the pronounced electronic band structure reconstruction due to many-body effects, which may be the key feature for understanding the physics of highly disordered metals.