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Title:Resistance fluctuation spectroscopy and other transport behavior in lanthanum barium copper oxide
Author(s):Weis, Adam Cole
Director of Research:Van Harlingen, Dale J.
Doctoral Committee Chair(s):MacDougall, Gregory
Doctoral Committee Member(s):Phillips, Philip W.; Lorenz, Virginia O.
Department / Program:Physics
Degree Granting Institution:University of Illinois at Urbana-Champaign
High-temperature superconductivity
pulsed-laser deposition
1/f noise
resistance fluctuations
lanthanum barium copper oxide
thin films
Abstract:In phase diagrams of cuprate high-temperature superconductors, superconductivity often occurs close to other phases of strongly correlated electron matter. In La(2-x)Ba(x)CuO(4) (LBCO), the critical temperature for superconductivity is anomalously suppressed at x = 1/8, and at the same doping, a “striped” ordering of spin and charge emerges. Although the charge striped phase is expected to include local resistance anisotropy, this has not been observed, and LBCO’s stripe behavior has only been studied by scattering experiments at beamline facilities. In this work, pulsed-laser deposition and microfabrication were used to create small- volume LBCO wires at dopings near x = 1/8. In such wires, low-frequency resistance- fluctuation spectra were measured at various dopings, temperatures, and bias currents. Material characterization studies by X-ray diffraction, atomic force microscopy, magnetometry, and resistance measurements were used to determine an optimized laser deposition recipe for superconducting LBCO films. The observed low-frequency resistance fluctuations in LBCO wires had behavior consistent with an ordered charge-stripe state in small, fluctuating domains. In most samples, the power spectral density of resistance noise increases as temperature is lowered below the charge-ordering temperatures expected for LBCO. The power spectral density of resistance fluctuations is found to scale with inverse frequency, consistent with the “1/ f ” noise that the Dutta-Horn model predicts for an ensemble of two-level systems. Additional observations — suppressed power spectral density at high currents and variation of noise with in-plane current direction — suggest that the resistance fluctuations have a stripe-like character. In summary, a process has been developed for consistent superconducting thin-film LBCO, and in these films, low-frequency resistance fluctuation spectroscopy has been demonstrated as a tool to study stripe-like charge ordering.
Issue Date:2017-12-08
Rights Information:Copyright 2017 by Adam Cole Weis
Date Available in IDEALS:2018-03-13
Date Deposited:2017-12

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