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Single crystals of Ce2PdIn8 were studied by means of magnetic susceptibility, electrical resistivity, and specific heat measurements. The compound was found to be a heavy fermion clean-limit superconductor with Tc=0.68 K. Most remarkably, the superconductivity in this system emerges out of the antiferromagnetic state that sets in at TN=10 K, and both cooperative phenomena coexist in a bulk at ambient pressure conditions.

The in-plane resistivity and thermal conductivity of the heavy-fermion superconductor Ce 2 PdIn 8 single crystals were measured down to 50 mK. A field-induced quantum critical point, occurring at the upper critical field H c2 , is demonstrated from the ðTÞ $ T near H c2 and ðTÞ $ T 2 when further increasing the field. The large residual linear term 0 =T at zero field and the rapid increase of ðHÞ=T at low field give evidence for nodal superconductivity in Ce 2 PdIn 8 . The jump of ðHÞ=T near H c2 suggests a first-order-like phase transition at low temperature. These results mimic the features of the famous CeCoIn 5 superconductor, implying that Ce 2 PdIn 8 may be another interesting compound to investigate for the interplay between magnetism and superconductivity. The interplay between magnetism and superconductivity has been a central issue for heavy-fermion superconductors [1], high-T c cuprates [2], and iron pnictides [3]. Among them, one particularly interesting case is the heavy-fermion superconductor CeCoIn 5 , with T c ¼ 2:3 K at ambient pressure [4]. Its superconducting gap has d-wave symmetry [5,6]. While there is no static magnetism in CeCoIn 5 at zero field, a field-induced antiferromagnetic (AF) quantum critical point (QCP) has been clearly demonstrated by resistivity and specific heat measurements [7,8]. Initially, it was very puzzling why the AF QCP is located right at the upper critical field H c2 .Meanwhile, the observations of first-order phase transition at low temperature and H c2 and a second magnetization and specific heat anomaly well inside the superconducting state have been interpreted as the signature of a Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) superconducting state [5,[9][10][11][12]. The novel FFLO state with broken spatial symmetry was predicted in the 1960s [13,14], but it has never been experimentally verified before. The possible FFLO state at the low-temperaturehigh-field (LTHF) corner of the H À T phase diagram of CeCoIn 5 has stimulated extensive studies [15].More recently, NMR, neutron scattering, and muon spin rotation ( SR) experiments have provided clear evidence for a field-induced magnetism in this LTHF part of the phase diagram [16][17][18][19][20][21]. It was identified as a spin-density wave (SDW) order with an incommensurate modulation Q ¼ ð0:44; 0:44; 0:5Þ. Interestingly, this SDW order disappears in the normal state above H c2 , showing that magnetic order and superconductivity in CeCoIn 5 are directly coupled [16,17]. While this has nicely explained the field-induced AF QCP at H c2 [7,8], the physical origin of this LTHF superconducting Q phase is still under debate. For example, Yanase and Sigrist have suggested that the incommensurate SDW order is stabilized in the FFLO state by the appearance of the Andreev bound state localized around the zeros of the FFLO order parameter [22]. Aperis, Varelogiannis, and Littlewood have argued that the Q phase is a pattern of coexisting condensates: a d-wave singlet superconducting state, a staggered -triplet superconducting s...

When a second-order magnetic phase transition is tuned to zero temperature by a nonthermal parameter, quantum fluctuations are critically enhanced, often leading to the emergence of unconventional superconductivity. In these "quantum critical" superconductors it has been widely reported that the normal-state properties above the superconducting transition temperature T c often exhibit anomalous non-Fermi liquid behaviors and enhanced electron correlations. However, the effect of these strong critical fluctuations on the superconducting condensate below T c is less well established. Here we report measurements of the magnetic penetration depth in heavy-fermion, iron-pnictide, and organic superconductors located close to antiferromagnetic quantum critical points, showing that the superfluid density in these nodal superconductors universally exhibits, unlike the expected T-linear dependence, an anomalous 3/2 power-law temperature dependence over a wide temperature range. We propose that this noninteger power law can be explained if a strong renormalization of effective Fermi velocity due to quantum fluctuations occurs only for momenta k close to the nodes in the superconducting energy gap Δ(k). We suggest that such "nodal criticality" may have an impact on low-energy properties of quantum critical superconductors. T he physics of materials located close to a quantum critical point (QCP) are an important issue because the critical fluctuations associated with this point may produce unconventional high-temperature superconductivity (1, 2). Quantum oscillations (3, 4) and specific heat measurements (5) have shown that, in some systems, as the material is tuned toward the QCP by controlling an external parameter such as doping, pressure, or magnetic field, the effective mass strongly increases due to enhanced correlation effects. Along with this the temperature dependence of the resistivity shows a strong deviation from the standard AT 2 dependence in the Fermi liquid (FL) theory of metals and often shows an anomalous T-linear behavior that corresponds to the A coefficient diverging as zero temperature is approached.Although there are many studies of non-FL behavior in the normal metallic state (1, 2), relatively little is known about how the QCP affects the superconducting properties below the critical temperature T c . The superconducting dome often develops around the putative QCP so that when the temperature is lowered below T c , the superconducting order parameter starts to develop and the Fermi surface becomes gapped. It is therefore natural to consider that the low-energy quantum critical fluctuations are quenched by the formation of the superconducting gap Δ, which means that the system avoids the anomalous singularities associated with the QCP. Perhaps because of this reasoning the superconducting properties are usually analyzed by the conventional theory without including temperature/field-dependent renormalization effects resulting from the proximity to the QCP. For example, in refs. 6 and 7 the NMR relaxat...