Unconventional Coherence Peak in Cuprate Superconductors
The Hebel-Slichter coherence peak, observed in the spin-lattice relaxation rate 1/T_{1} just below the critical temperature T_{c}, serves as a crucial experimental validation of the Bardeen-Cooper-Schrieffer pairing symmetry in conventional superconductors. However, no coherence peak in 1/T_{1} has...
Saved in:
| Main Authors: | , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
American Physical Society
2024-12-01
|
| Series: | Physical Review X |
| Online Access: | http://doi.org/10.1103/PhysRevX.14.041072 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Summary: | The Hebel-Slichter coherence peak, observed in the spin-lattice relaxation rate 1/T_{1} just below the critical temperature T_{c}, serves as a crucial experimental validation of the Bardeen-Cooper-Schrieffer pairing symmetry in conventional superconductors. However, no coherence peak in 1/T_{1} has been observed in unconventional superconductors like cuprates. In this study, an unconventional coherence peak is identified for the first time using nuclear quadrupole resonance on YBa_{2}Cu_{4}O_{8}, pointing to a distinctive pairing symmetry. The spin-lattice relaxation rate in nuclear quadrupole resonance and nuclear magnetic resonance with nuclear spin I>1/2 comprises the magnetic relaxation rate 1/T_{1}^{mag}, which probes magnetic fluctuations, and the quadrupole relaxation rate 1/T_{1}^{quad}, which probes charge fluctuations. By utilizing ^{63}Cu and ^{65}Cu isotopes, we successfully distinguish 1/T_{1}^{mag} and 1/T_{1}^{quad} of YBa_{2}Cu_{4}O_{8} and reveal the presence of the coherence peak in 1/T_{1}^{quad} but not in 1/T_{1}^{mag}, in contrast to conventional superconductors. Our finding demonstrates that unconventional superconductors do not exhibit a coherence peak in 1/T_{1} when the relaxation is due to fluctuations of the hyperfine field. Conversely, a coherence peak is expected when the relaxation is caused by electric field gradient fluctuations, due to the different coherence factors between charge and magnetic fluctuations. Our successful measurements of 1/T_{1} for the chains of YBa_{2}Cu_{4}O_{8} suggest that, should the conditions for predominant quadrupole relaxation be satisfied, this phenomenon could provide a novel approach to exploring the unconventional nature of the pairing mechanism in other superconductors. |
|---|---|
| ISSN: | 2160-3308 |