TY - JOUR
T1 - Tuning the Distance to a Possible Ferromagnetic Quantum Critical Point in A2Cr3As3
AU - Luo, J.
AU - Yang, J.
AU - Zhou, R.
AU - Mu, Q. G.
AU - Liu, T.
AU - Ren, Zhi An
AU - Yi, C. J.
AU - Shi, Y. G.
AU - Zheng, Guo Qing
N1 - Funding Information:
We thank G. H. Cao, Y. Haga, J. P. Hu, H. Kontani, K. Miyake, A. Sumiyama, Z. Q. Wang, H. M. Weng, G. M. Zhang, and Y. Zhou for helpful discussions, and C. G. Wang for technical assistance. This work was partially supported by NSFC Grants (No. 11674377, No. 11634015, and No. 11774399), MOST Grants (No. 2016YFA0300502, No. 2017YFA0302901, and No. 2017YFA0302904), as well as JSPS/MEXT Grants (No. JP15H05852 and No. JP19H00657). J. Y. also acknowledges support by the Youth Innovation Promotion Association of CAS.
Publisher Copyright:
© 2019 American Physical Society.
Copyright:
Copyright 2019 Elsevier B.V., All rights reserved.
PY - 2019/7/24
Y1 - 2019/7/24
N2 - Although superconductivity in the vicinity of an antiferromagnetic (AFM) instability has been extensively explored in the last three decades or so, superconductivity in compounds with a background of ferromagnetic (FM) spin fluctuations is still rare. We report As75 nuclear quadrupole resonance measurements on the A2Cr3As3 family, which is the first group of Cr-based superconductors at ambient pressure, with A being alkali elements. From the temperature dependence of the spin-lattice relaxation rate (1/T1), we find that by changing A in the order of A=Na, Na0.75K0.25, K, and Rb, the system is tuned to approach a possible FM quantum critical point (QCP). This may be ascribed to the Cr2-As2-Cr2 bond angle that decreases towards 90°, which enhances the FM interaction via the Cr2-As2-Cr2 path. Upon moving away from the QCP, the superconducting transition temperature Tsc increases progressively up to 8.0 K in Na2Cr3As3, which is in sharp contrast to the AFM case where Tsc usually shows a maximum around a QCP. The 1/T1 decreases rapidly below Tsc with no Hebel-Slichter peak, and ubiquitously follows a T5 variation below a characteristic temperature T∗≈0.6 Tsc, which indicates the existence of point nodes in the superconducting gap function commonly in the family. These results suggest that the A2Cr3As3 family is a possible solid-state analog of superfluid He3.
AB - Although superconductivity in the vicinity of an antiferromagnetic (AFM) instability has been extensively explored in the last three decades or so, superconductivity in compounds with a background of ferromagnetic (FM) spin fluctuations is still rare. We report As75 nuclear quadrupole resonance measurements on the A2Cr3As3 family, which is the first group of Cr-based superconductors at ambient pressure, with A being alkali elements. From the temperature dependence of the spin-lattice relaxation rate (1/T1), we find that by changing A in the order of A=Na, Na0.75K0.25, K, and Rb, the system is tuned to approach a possible FM quantum critical point (QCP). This may be ascribed to the Cr2-As2-Cr2 bond angle that decreases towards 90°, which enhances the FM interaction via the Cr2-As2-Cr2 path. Upon moving away from the QCP, the superconducting transition temperature Tsc increases progressively up to 8.0 K in Na2Cr3As3, which is in sharp contrast to the AFM case where Tsc usually shows a maximum around a QCP. The 1/T1 decreases rapidly below Tsc with no Hebel-Slichter peak, and ubiquitously follows a T5 variation below a characteristic temperature T∗≈0.6 Tsc, which indicates the existence of point nodes in the superconducting gap function commonly in the family. These results suggest that the A2Cr3As3 family is a possible solid-state analog of superfluid He3.
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U2 - 10.1103/PhysRevLett.123.047001
DO - 10.1103/PhysRevLett.123.047001
M3 - Article
C2 - 31491262
AN - SCOPUS:85069969101
VL - 123
JO - Physical Review Letters
JF - Physical Review Letters
SN - 0031-9007
IS - 4
M1 - 047001
ER -