Connecting two classes of unconventional superconductors: Pressure-tuning of CeFeAs

The understanding of unconventional superconductivity is one of the most challenging and fascinating tasks of solid-state physics. Different classes of unconventional superconductors share that superconductivity emerges near a magnetic phase despite the underlying physics appears to be different. Two of these are the heavy-fermion and the iron-based superconductors.
We present results of a hydrostatic pressure study on single crystals of CeFeAsO, a parent compound to iron-based superconductors, using diamond anvil pressure cells. By electrical, magnetic, and structural measurements, we show that upon increasing the applied pressure, the material characteristics of CeFeAsO change from that of an iron-pnictide material to that of a heavy-fermion metal [1]. In the border region, where the iron spin-density-wave magnetism disappears and signatures of Kondo-physics, a hallmark of Ce-based heavy-fermion metals, develop, a narrow superconducting phase emerges. This suggests that the two major phenomena characterizing iron-pnictides and heavy-fermions, iron spin-density-wave magnetism and the Kondo-effect, work together to produce superconductivity in CeFeAsO.

[1] K. Mydeen et al., Phys. Rev. Lett. 125, 207001 (2020).

In collaboration with K. Mydeen, A. Jesche, K. Meier-Kirchner, U. Schwarz, C. Geibel, and H. Rosner.

E-mail for corresponding author: [email protected]