From Atomistic Impurity Landscapes to Two-Level-System Distributions and Microwave Loss: Hydrogen-Induced Losses in Nb$_2$O$_{5-δ}$ and Ta$_2$O$_{5-δ}$

Cristóbal Méndez; Tomás A. Arias; Sarvesh Chaudhari

paper

From Atomistic Impurity Landscapes to Two-Level-System Distributions and Microwave Loss: Hydrogen-Induced Losses in Nb $_{2}$ O $_{5 - δ}$ and Ta $_{2}$ O $_{5 - δ}$

arXiv:2603.17194

Abstract

We introduce a first-principles-guided framework for predicting statistical TLS distributions from mobile impurities in disordered materials. Machine-learned interatomic potentials, with DFT and minimum-action-path validation, connect impurity landscapes to tunnel-splitting and asymmetry distributions, TLS densities, and dielectric loss. Applied to amorphous Nb $_{2}$ O $_{5 - δ}$ and Ta $_{2}$ O $_{5 - δ}$ , the framework implicates interstitial hydrogen as a source of microwave loss. Loss tangents match Nb-pentoxide measurements at inferred H concentrations, while weaker H uptake in Ta reproduces the Nb/Ta TLS contrast.

From Atomistic Impurity Landscapes to Two-Level-System Distributions and Microwave Loss: Hydrogen-Induced Losses in Nb2​O5−δ​ and Ta2​O5−δ​

Abstract

From Atomistic Impurity Landscapes to Two-Level-System Distributions and Microwave Loss: Hydrogen-Induced Losses in Nb $_{2}$ O $_{5 - δ}$ and Ta $_{2}$ O $_{5 - δ}$