Strong interplay between stripe spin fluctuations, nematicity and superconductivity in FeSe

• Published in: Nature materials Vol. 15; no. 2; pp. 159 - 163
• Main Authors: Wang, Qisi, Shen, Yao, Pan, Bingying, Hao, Yiqing, Ma, Mingwei, Zhou, Fang, Steffens, P., Schmalzl, K., Forrest, T. R., Abdel-Hafiez, M., Chen, Xiaojia, Chareev, D. A., Vasiliev, A. N., Bourges, P., Sidis, Y., Cao, Huibo, Zhao, Jun
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01-02-2016; Nature Publishing Group
• Subjects: 639/766/119/1003; 639/766/119/997; Biomaterials; Condensed Matter; Condensed Matter Physics; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Cooling; Fluctuation; Fluctuations; Iron; Joining; letter; Magnetic properties and materials; Materials Science; Nanotechnology; Nematic; Neutrons; Optical and Electronic Materials; Order disorder; Physics; Proposals; Resonance; Spectrum analysis; Strongly Correlated Electrons; Superconducting properties and materials; Superconductivity; Superconductors
• ISSN: 1476-1122; 1476-4660
• DOI: 10.1038/nmat4492

Neutron scattering measurements provide evidence for strong coupling between stripe spin fluctuations, nematicity and superconductivity in single-crystalline FeSe.
In iron-based superconductors the interactions driving the nematic order (that breaks four-fold rotational symmetry in the iron plane) may also mediate the Cooper pairing
1
. The experimental determination of these interactions, which are believed to depend on the orbital or the spin degrees of freedom
1
,
2
,
3
,
4
, is challenging because nematic order occurs at, or slightly above, the ordering temperature of a stripe magnetic phase
1
,
5
. Here, we study FeSe (ref. 
6
)—which exhibits a nematic (orthorhombic) phase transition at
T
s
= 90 K without antiferromagnetic ordering—by neutron scattering, finding substantial stripe spin fluctuations coupled with the nematicity that are enhanced abruptly on cooling through
T
s
. A sharp spin resonance develops in the superconducting state, whose energy (∼4 meV) is consistent with an electron–boson coupling mode revealed by scanning tunnelling spectroscopy
7
. The magnetic spectral weight in FeSe is found to be comparable to that of the iron arsenides
8
,
9
. Our results support recent theoretical proposals that both nematicity and superconductivity are driven by spin fluctuations
1
,
10
,
11
,
12
,
13
.