An intrinsic order parameter relevant to quantum criticality, which leads to exotic nature of superconductivity, has been unidentified in the prototypical unconventional superconductor CeCoIn5. The authors demonstrate that heterogeneous antiferromagnetic order develops above superconducting upper critical fields when Zn ions are slightly doped into CeCoIn5. The breaking of the antiferromagnetic order by magnetic field yields logarithmic diverging behavior toward zero temperature in specific heat, which is a hallmark of quantum criticality. These findings provide evidence that the quantum criticality in CeCoIn5 originates from the order parameter corresponding to the field-induced antiferromagnetic state observed in the Zn-doped systems.
The article regarding this work:
M. Yokoyama, Y. Honma, Y. Oshima, Rahmanto, K. Suzuki, K. Tenya, Y. Shimizu, D. Aoki, A. Matsuo, K. Kindo, S. Nakamura, Y. Kono, S. Kittaka, and T. Sakakibara:
"Nature of field-induced antiferromagnetic order in Zn-doped CeCoIn5 and its connection to quantum criticality in the pure compound",
Physical Review B 105, 054515 (2022).
link to this paper