Search

In a conventional superconductor, the binding of electrons into the paired states that collectively carry the supercurrent is mediated by phonons — vibrations of the crystal lattice. Here we argue that, in the case of the heavy fermion superconductors CePd2Si2 and CeIn3, the charge carriers are bound together in pairs by magnetic spin–spin interactions. The existence of magnetically mediated superconductivity in these compounds could help shed light on the question of whether magnetic interactions are relevant for describing the superconducting and normal-state properties of other strongly correlated electron systems, perhaps including the high-temperature copper oxide superconductors.

Close to the border of antiferromagnetic order at high pressure the cubic stoichiometric compound CeIn 3 displays an unconventional normal-state resistivity followed by superconductivity at low temperatures. The superconducting transition temperature varies rapidly with pressure near the critical pressure where the Neel temperature collapses towards absolute zero.

The magnetic ordering temperature of some rare earth based heavy fermion compounds is strongly pressure-dependent and can be completely suppressed at a critical pressure, p$_c$, making way for novel correlated electron states close to this quantum critical point. We have studied the clean heavy fermion antiferromagnets CePd$_2$Si$_2$ and CeIn$_3$ in a series of resistivity measurements at high pressures up to 3.2 GPa and down to temperatures in the mK region. In both materials, superconductivity appears in a small window of a few tenths of a GPa on either side of p$_c$. We present detailed measurements of the superconducting and magnetic temperature-pressure phase diagram, which indicate that superconductivity in these materials is enhanced, rather than suppressed, by the closeness to magnetic order., Comment: 11 pages, including 9 figures

Metals on the border of magnetism have attracted great attention in recent times, as a number of them exhibit a superconducting phase at low temperatures in the vicinity of the critical pressure at which the magnetic transition temperature is suppressed to zero. We present a brief overview and comparison of the body centred tetragonal compounds CePd2Si2 and CeNi2Ge2, and the simple cubic CeIn3. In spite of the differences in structure and the detailed behaviour in the unconventional normal state near the critical pressure, these compounds share the existence of superconductivity at the border of antiferromagnetic order, and therefore are prime candidates for the study of a possible magnetic pairing mechanism. In this paper, we will solely present a comparison of the normal state properties of these materials.