Possible Heavy-Fermion-like Behavior in Wide-Bandgap Semiconductor Ta2O5

We investigated the electronic structures of the wide-bandgap semiconductor Ta2O5 in the presence of oxygen vacancies using standard density functional theory. The emergence of flat bands is observed in certain structural phases due to these vacancies. For instance, when the concentration of oxygen vacancies reaches 10% in the γ1, B, and δ phases of Ta2O5, a flat band appears near the Fermi energy. Further analysis reveals that in certain regions within the Brillouin zone, electrons in flat bands exhibit effective masses 103 times larger than that of free electrons, with some locations even being 104 times higher, thus demonstrating pronounced heavy-fermion-like behavior. Experimental schemes based on electron cyclotron resonance for the detection of such behavior are suggested.