Abstract
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.
| Original language | English |
|---|---|
| Article number | 047001 |
| Journal | Physical Review Letters |
| Volume | 123 |
| Issue number | 4 |
| DOIs | |
| Publication status | Published - Jul 24 2019 |
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ASJC Scopus subject areas
- Physics and Astronomy(all)
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Tuning the Distance to a Possible Ferromagnetic Quantum Critical Point in A2Cr3As3. / Luo, J.; Yang, J.; Zhou, R.; Mu, Q. G.; Liu, T.; Ren, Zhi An; Yi, C. J.; Shi, Y. G.; Zheng, Guo-Qing.
In: Physical Review Letters, Vol. 123, No. 4, 047001, 24.07.2019.Research output: Contribution to journal › Article
}
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
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
VL - 123
JO - Physical Review Letters
JF - Physical Review Letters
SN - 0031-9007
IS - 4
M1 - 047001
ER -