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Title: London penetration depth measurements in Ba (Fe 1-xT x) 2As 2(T=Co,Ni,Ru,Rh,Pd,Pt,Co+Cu) superconductors

Abstract

The London penetration depth has been measured in various doping levels of single crystals of Ba(Fe 1-xT x) 2As 2 (T=Co,Ni,Ru,Rh,Pd,Pt,Co+Cu) superconductors by utilizing a tunnel diode resonator (TDR) apparatus. All in-plane penetration depth measurements exhibit a power law temperature dependence of the form Δλ ab(T) = CT n, indicating the existence of low-temperature, normal state quasiparticles all the way down to the lowest measured temperature, which was typically 500 mK. Several different doping concentrations from the Ba(Fe 1-xT x) 2As 2 (T=Co,Ni) systems have been measured and the doping dependence of the power law exponent, n, is compared to results from measurements of thermal conductivity and specific heat. In addition, a novel method has been developed to allow for the measurement of the zero temperature value of the in-plane penetration depth, λ ab(0), by using TDR frequency shifts. By using this technique, the doping dependence of λ ab(0) has been measured in the Ba(Fe 1-xCo x) 2As 2 series, which has allowed also for the construction of the doping-dependent superfluid phase stiffness, ρ s(T) = [λ(0)/λ(T)] 2. By studying the effects of disorder on these superconductors using heavy ion irradiation, it has been determined that the observed power lawmore » temperature dependence likely arises from pair-breaking impurity scattering contributions, which is consistent with the proposed s±-wave symmetry of the superconducting gap in the dirty scattering limit. This hypothesis is supported by the measurement of an exponential temperature dependence of the penetration depth in the intrinsically clean LiFeAs, indicative of a nodeless superconducting gap.« less

Authors:
 [1]
  1. Iowa State Univ., Ames, IA (United States)
Publication Date:
Research Org.:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1029556
Report Number(s):
IS-T 3019
DOE Contract Number:  
AC02-07CH11358
Resource Type:
Thesis/Dissertation
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY

Citation Formats

Gordon, Ryan T. London penetration depth measurements in Ba (Fe1-xTx)2As2(T=Co,Ni,Ru,Rh,Pd,Pt,Co+Cu) superconductors. United States: N. p., 2011. Web. doi:10.2172/1029556.
Gordon, Ryan T. London penetration depth measurements in Ba (Fe1-xTx)2As2(T=Co,Ni,Ru,Rh,Pd,Pt,Co+Cu) superconductors. United States. doi:10.2172/1029556.
Gordon, Ryan T. Sat . "London penetration depth measurements in Ba (Fe1-xTx)2As2(T=Co,Ni,Ru,Rh,Pd,Pt,Co+Cu) superconductors". United States. doi:10.2172/1029556. https://www.osti.gov/servlets/purl/1029556.
@article{osti_1029556,
title = {London penetration depth measurements in Ba (Fe1-xTx)2As2(T=Co,Ni,Ru,Rh,Pd,Pt,Co+Cu) superconductors},
author = {Gordon, Ryan T.},
abstractNote = {The London penetration depth has been measured in various doping levels of single crystals of Ba(Fe1-xTx)2As2 (T=Co,Ni,Ru,Rh,Pd,Pt,Co+Cu) superconductors by utilizing a tunnel diode resonator (TDR) apparatus. All in-plane penetration depth measurements exhibit a power law temperature dependence of the form Δλab(T) = CTn, indicating the existence of low-temperature, normal state quasiparticles all the way down to the lowest measured temperature, which was typically 500 mK. Several different doping concentrations from the Ba(Fe1-xTx)2As2 (T=Co,Ni) systems have been measured and the doping dependence of the power law exponent, n, is compared to results from measurements of thermal conductivity and specific heat. In addition, a novel method has been developed to allow for the measurement of the zero temperature value of the in-plane penetration depth, λab(0), by using TDR frequency shifts. By using this technique, the doping dependence of λab(0) has been measured in the Ba(Fe1-xCox)2As2 series, which has allowed also for the construction of the doping-dependent superfluid phase stiffness, ρs(T) = [λ(0)/λ(T)]2. By studying the effects of disorder on these superconductors using heavy ion irradiation, it has been determined that the observed power law temperature dependence likely arises from pair-breaking impurity scattering contributions, which is consistent with the proposed s±-wave symmetry of the superconducting gap in the dirty scattering limit. This hypothesis is supported by the measurement of an exponential temperature dependence of the penetration depth in the intrinsically clean LiFeAs, indicative of a nodeless superconducting gap.},
doi = {10.2172/1029556},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2011},
month = {1}
}

Thesis/Dissertation:
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