TY - JOUR
T1 - Disorder-induced topological change of the superconducting gap structure in iron pnictides
AU - Mizukami, Y.
AU - Konczykowski, M.
AU - Kawamoto, Y.
AU - Kurata, S.
AU - Kasahara, S.
AU - Hashimoto, K.
AU - Mishra, V.
AU - Kreisel, A.
AU - Wang, Y.
AU - Hirschfeld, P. J.
AU - Matsuda, Y.
AU - Shibauchi, T.
N1 - Funding Information:
We thank C.J. van der Beek, A. Carrington, H. Kontani and R. Prozorov for fruitful discussion. We also thank B. Boizot, J. Losco and V. Metayer for technical assistance. This work was supported by Grants-in-Aid for Scientific Research (KAKENHI) from Japan Society for the Promotion of Science (JSPS), and by the ‘Topological Quantum Phenomena’ (No. 25103713) Grant-in Aid for Scientific Research on Innovative Areas from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan. Irradiation experiments were supported by EMIR network, proposal No. 11-10-8071. V.M. acknowledges support from the Center for Emergent Superconductivity, an Energy Frontier Research Center funded by the US DOE, Office of Science, under Award No. DE-AC0298CH1088. A.K., Y.W. and P.J.H. were supported by DOE DE-FG02-05ER46236.
Publisher Copyright:
©2014 Macmillan Publishers Limited. All rights reserved.
PY - 2014/12
Y1 - 2014/12
N2 - In superconductors with unconventional pairing mechanisms, the energy gap in the excitation spectrum often has nodes, which allow quasiparticle excitations at low energies. In many cases, such as in d-wave cuprate superconductors, the position and topology of nodes are imposed by the symmetry, and thus the presence of gapless excitations is protected against disorder. Here we report on the observation of distinct changes in the gap structure of iron-pnictide superconductors with increasing impurity scattering. By the successive introduction of nonmagnetic point defects into BaFe2(As 1-x P x) 2 crystals via electron irradiation, we find from the low-temperature penetration depth measurements that the nodal state changes to a nodeless state with fully gapped excitations. Moreover, under further irradiation the gapped state evolves into another gapless state, providing bulk evidence of unconventional sign-changing s-wave superconductivity. This demonstrates that the topology of the superconducting gap can be controlled by disorder, which is a strikingly unique feature of iron pnictides.
AB - In superconductors with unconventional pairing mechanisms, the energy gap in the excitation spectrum often has nodes, which allow quasiparticle excitations at low energies. In many cases, such as in d-wave cuprate superconductors, the position and topology of nodes are imposed by the symmetry, and thus the presence of gapless excitations is protected against disorder. Here we report on the observation of distinct changes in the gap structure of iron-pnictide superconductors with increasing impurity scattering. By the successive introduction of nonmagnetic point defects into BaFe2(As 1-x P x) 2 crystals via electron irradiation, we find from the low-temperature penetration depth measurements that the nodal state changes to a nodeless state with fully gapped excitations. Moreover, under further irradiation the gapped state evolves into another gapless state, providing bulk evidence of unconventional sign-changing s-wave superconductivity. This demonstrates that the topology of the superconducting gap can be controlled by disorder, which is a strikingly unique feature of iron pnictides.
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U2 - 10.1038/ncomms6657
DO - 10.1038/ncomms6657
M3 - Article
AN - SCOPUS:84922672327
VL - 5
JO - Nature Communications
JF - Nature Communications
SN - 2041-1723
M1 - 5657
ER -