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Title: Elucidating the local atomic and electronic structure of amorphous oxidized superconducting niobium films

Journal Article · · Applied Physics Letters
DOI: https://doi.org/10.1063/5.0069549 · OSTI ID:1861062
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [3]; ORCiD logo [4]; ORCiD logo [1];  [1];  [1];  [5]; ORCiD logo [1];  [6]; ORCiD logo [1]
  1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); King's College, London (United Kingdom)
  3. Univ. of California, Berkeley, CA (United States)
  4. National Institute of Standards and Technology, Gaithersburg, MD (United States)
  5. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States)
  6. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
+ Show Author Affiliations

Qubits made from superconducting materials are a mature platform for quantum information science application, such as quantum computing. However, material-based losses are now a limiting factor in reaching the coherence times needed for applications. In particular, knowledge of the atomistic structure and properties of the circuit materials is needed to identify, understand, and mitigate material-based decoherence channels. Here, we characterize the atomic structure of the native oxide film formed on Nb resonators by comparing fluctuation electron microscopy experiments to density functional theory calculations, finding that an amorphous layer is consistent with an Nb2O5 stoichiometry. Comparing x-ray absorption measurements at the Oxygen K edge with first-principles calculations, we find evidence of d-type magnetic impurities in our sample, known to cause impedance in proximal superconductors. This work identifies the structural and chemical composition of the oxide layer grown on Nb superconductors and shows that soft x-ray absorption can fingerprint magnetic impurities in these superconducting systems.

Research Organization:
Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
Sponsoring Organization:
Engineering and Physical Sciences Research Council (EPSRC); National Science Foundation (NSF); US Air Force Office of Scientific Research (AFOSR); US-Irish Fulbright Commission; USDOE; USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division
Grant/Contract Number:
AC02-05CH11231
OSTI ID:
1861062
Journal Information:
Applied Physics Letters, Journal Name: Applied Physics Letters Journal Issue: 24 Vol. 119; ISSN 0003-6951
Publisher:
American Institute of Physics (AIP)Copyright Statement
Country of Publication:
United States
Language:
English

References (40)

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Amorphous Niobium Oxide Structures Calculated from First Principles using Density Functional Theory and Molecular Dynamics dataset January 2021
Calculated O K-edge XAS Spectra of Niobium Oxide Phases using Bethe-Salpeter equation dataset January 2021
Calculated O K-edge XAS Spectra of Niobium Oxide Phases using Bethe-Salpeter equation dataset January 2021

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75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
density functional theory
electron microscopy
electronic structure
emerging qubit systems - novel materials, encodings, and architectures
first-principle calculations
machine learning
quantum computing
quantum information
superconductors
thin films
x-ray absorption spectroscopy