Iron Based Superconductors

@article{Vinograd2021,

title = {Inhomogeneous Knight shift in vortex cores of superconducting FeSe},

author = {I. Vinograd and S. P. Edwards and Z. Wang and T. Kissikov and J. K. Byland and J. R. Badger and V. Taufour and N. J. Curro},

doi = {10.1103/physrevb.104.014502},

year  = {2021},

date = {2021-07-01},

journal = {Phys. Rev. B},

volume = {104},

number = {1},

pages = {014502},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{NMRnematicStrainBa122PRB2016,

title = {NMR study of nematic spin fluctuations in a detwinned single crystal of underdoped Ba(Fe$_1-x$Co$_x$)$_2$As$_2$},

author = {T. Kissikov and A. P. Dioguardi and E. I. Timmons and M. A. Tanatar and R. Prozorov and S. L. Bud'ko and P. C. Canfield and R. M. Fernandes and N. J. Curro},

url = {http://link.aps.org/doi/10.1103/PhysRevB.94.165123},

doi = {10.1103/PhysRevB.94.165123},

year  = {2016},

date = {2016-10-01},

journal = {Phys. Rev. B},

volume = {94},

pages = {165123},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{DioguardiPdoped2015,

title = {NMR Evidence for Inhomogeneous Nematic Fluctuations in BaFe$_2$As$_2-x$P$_x$},

author = {A. P. Dioguardi and T. Kissikov and C. H. Lin and K. R. Shirer and M. M. Lawson and H. -J. Grafe and J. -H. Chu and I. R. Fisher and R. M. Fernandes and N. J. Curro},

url = {http://link.aps.org/doi/10.1103/PhysRevLett.116.107202},

doi = {10.1103/PhysRevLett.116.107202},

year  = {2016},

date = {2016-03-01},

journal = {Phys. Rev. Lett.},

volume = {116},

pages = {107202},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Dioguardi2015,

title = {NMR evidence for inhomogeneous glassy behavior driven by nematic fluctuations in iron arsenide superconductors},

author = {A. P. Dioguardi and M. M. Lawson and B. T. Bush and J. Crocker and K. R. Shirer and D. M. Nisson and T. Kissikov and S. Ran and S. L. Budko and P. C. and Canfield},

url = {http://dx.doi.org/10.1103/PhysRevB.92.165116},

doi = {10.1103/physrevb.92.165116},

issn = {1550-235X},

year  = {2015},

date = {2015-10-01},

journal = {Phys. Rev. B},

volume = {92},

number = {16},

pages = {165116},

publisher = {American Physical Society (APS)},

abstract = {We present As75 nuclear magnetic resonance spin-lattice and spin-spin relaxation rate data in Ba(Fe1-xCox)2As2 and Ba(Fe1-xCux)2As2 as a function of temperature, doping, and magnetic field. The relaxation curves exhibit a broad distribution of relaxation rates, consistent with inhomogeneous glassy behavior up to 100 K. The doping and temperature response of the width of the dynamical heterogeneity is similar to that of the nematic susceptibility measured by elastoresistance measurements. We argue that quenched random fields which couple to the nematic order give rise to a nematic glass that is reflected in the spin dynamics.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{HajoPRB2014,

title = {Identical spin fluctuations in Cu- and Co-doped BaFe$_2$As$_2$ independent of electron doping},

author = {H. -J. Grafe and U. Gräfe and A. P. Dioguardi and N. J. Curro and S. Aswartham and S. Wurmehl and B. Büchner},

url = {http://link.aps.org/doi/10.1103/PhysRevB.90.094519},

doi = {10.1103/PhysRevB.90.094519},

year  = {2014},

date = {2014-09-01},

journal = {Phys. Rev. B},

volume = {90},

pages = {094519},

publisher = {American Physical Society},

abstract = {We present As75 nuclear magnetic resonance measurements on single crystals of BaFe2As2, BaFe1.8Co0.2As2, and BaFe1.82Cu0.18As2. While only Co doping induces bulk superconductivity on a broad doping range, the spin fluctuations probed by the nuclear spin-lattice relaxation rate (T1T)^-1 are identical for both dopings down to Tc. Below this temperature, (T1T)^-1 of the Cu-doped sample continues to rise, proving that (a) there is a quantum critical point below the superconducting dome, and (b) adding electrons does not affect the spin fluctuations. Consequently, we analyze the Knight shift data in terms of a two-component scenario, with one hyperfine coupling to an itinerant degree of freedom and the other to Fe moments.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Xiao2012,

title = {Evidence for filamentary superconductivity nucleated at antiphase domain walls in antiferromagnetic CaFe$_2$As$_2$},

author = {H. Xiao and T. Hu and A. P. Dioguardi and N. apRoberts-Warren and A. C. Shockley and J. Crocker and D. M. Nisson and Z. Viskadourakis and Xianyang Tee and I. Radulov and C. C. Almasan and N. J. Curro and C. Panagopoulos},

doi = {10.1103/PhysRevB.85.024530},

issn = {1098-0121},

year  = {2012},

date = {2012-01-01},

journal = {Phys. Rev. B},

volume = {85},

number = {2},

pages = {024530},

abstract = {Resistivity, magnetization, and microscopic As-75 nuclear magnetic resonance (NMR) measurements in the antiferromagnetically ordered state of the iron-based superconductor parent material CaFe2As2 exhibit anomalous features that are consistent with the collective freezing of domain walls. Below T* approximate to 10 K, the resistivity exhibits a peak and downturn, the bulk magnetization exhibits a sharp increase, and As-75 NMR measurements reveal the presence of slow fluctuations of the hyperfine field. These features in both the charge and spin response are strongly field dependent, are fully suppressed by H* approximate to 15 T, and suggest the presence of filamentary superconductivity nucleated at the antiphase domain walls in this material.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Dioguardi2012,

title = {Local magnetic inhomogeneities observed via $^75$As NMR in Ba(Fe$_1-x$Ni$_x$)$_2$As$_2$ with $H_0 perp c$-axis},

author = {A P Dioguardi and N apRoberts-Warren and A C Shockley and S L Bud'ko and N Ni and P C Canfield and N J Curro},

doi = {10.1088/1742-6596/344/1/012022},

year  = {2012},

date = {2012-01-01},

journal = {J. Phys: Conf. Ser.},

volume = {344},

number = {1},

pages = {012022},

abstract = {We present field-swept 75 As Nuclear Magnetic Resonance (NMR) measurements in the spin-density wave (SDW) state of Ba(Fe,Ni)2As2 for x = 0.0072. The large single crystals were aligned with the external field H0 perpendicular to the c axis. The spectra are increasingly broadened as a function of doping, and are well fit by a model of a commensurate SDW with local impurities.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Baek2009d,

title = {NMR Investigation of Superconductivity and Antiferromagnetism in CaFe$_2$As$_2$ under Pressure},

author = {S. -H. Baek and H. Lee and S. E. Brown and N. J. Curro and E. D. Bauer and F. Ronning and T. Park and J. D. Thompson},

doi = {10.1103/PhysRevLett.102.227601},

issn = {0031-9007},

year  = {2009},

date = {2009-06-01},

journal = {Phys. Rev. Lett.},

volume = {102},

number = {22},

pages = {227601},

abstract = {We report As-75 NMR measurements in CaFe2As2, made under applied pressures up to 0.83 GPa produced by a standard clamp pressure cell. Our data reveal phase segregation of paramagnetic and antiferromagnetic (AFM) phases over a range of pressures, with the AFM phase more than 90% dominant at low temperatures. In situ rf susceptibility measurements indicate the presence of superconductivity. As-75 spin-lattice relaxation experiments indicate that the As-75 nuclei sample the superconductivity while in the magnetically ordered environment.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Grafe2008,

title = {$^75$As NMR studies of superconducting LaFeAsO$_0.9$F$_0.1$},

author = {H. -J. Grafe and D. Paar and G. Lang and N. J. Curro and G. Behr and J. Werner and J. Hamann-Borrero and C. Hess and N. Leps and R. Klingeler and B. Buechner},

doi = {10.1103/PhysRevLett.101.047003},

issn = {0031-9007},

year  = {2008},

date = {2008-07-01},

journal = {Phys. Rev. Lett.},

volume = {101},

number = {4},

pages = {047003},

abstract = {We have performed (75)As nuclear magnetic resonance measurements on aligned powders of the new LaFeAsO(0.9)F(0.1) superconductor. In the normal state, we find a strong temperature dependence of the spin shift and Korringa behavior of the spin lattice relaxation rate. In the superconducting state, we find evidence for line nodes in the superconducting gap and spin-singlet pairing. Our measurements reveal a strong anisotropy of the spin lattice relaxation rate, which suggests that superconducting vortices contribute to the relaxation rate when the field is parallel to the c axis but not for the perpendicular direction.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}