Quasi-two-dimensional Fermi surfaces of the heavy-fermion superconductorCe2PdIn8

Abstract

We report low-temperature de Haas-van Alphen (dHvA) effect measurements in magnetic fields up to 35 T of the heavy-fermion superconductor Ce2PdIn8. The comparison of the experimental results with band-structure calculations implies that the 4f electrons are itinerant rather than localized. The cyclotron masses estimated at high field are only moderately enhanced, 8 and 14 m0, but are substantially larger than the corresponding band masses. The observed angular dependence of the dHvA frequencies suggests quasi-two-dimensional Fermi surfaces in agreement with band-structure calculations. However, the deviation from ideal two dimensionality is larger than in CeCoIn5, with which Ce2PdIn8 bears a lot of similarities. This subtle distinction accounts for the different superconducting critical temperatures of the two compounds. The appearance of unconventional superconductivity in the vicinity of a quantum critical point (QCP) is a common trend in Ce-based heavy-fermion (HF) compounds. A more recent and still somewhat controversial issue is the influence of the Fermi-surface (FS) dimensionality on unconventional superconductivity. Indeed, reduced dimensionality of the FS leads to nesting-type magnetic instabilities [1] and thus enhances the superconductivity [2,3]. The exact knowledge of the FS topology of HF systems is, therefore, essential. In addition, this information allows distinguishing if the f electrons are itinerant or localized, i.e. whether they contribute to the FS or not.Ce 2 PdIn 8 is a recently discovered HF superconductor with T c = 0.7 K and a non-magnetic ground state [4,5]. Non-Fermi-liquid behavior was observed in both macroscopic [6-10] and microscopic [11,12] measurements at low temperature, implying that Ce 2 PdIn 8 is located very close to a QCP. It was further suggested that a twodimensional (2D) SDW-type QCP is induced by magnetic field near the upper critical field, H c2 ≈ 2 T [9]. Unconventional superconductivity was demonstrated to be due to antiferromagnetic quantum fluctuations [13]. These unusual properties are strikingly similar to those of the well-studied HF superconductor CeCoIn 5 [14-17], which is also located very close to a QCP at ambient pressure. However, the superconducting critical temperature T c = 2.3 K of CeCoIn 5 [18] is considerably higher than that of Ce 2 PdIn 8 .Ce 2 PdIn 8 crystallizes into a tetragonal Ho 2 CoGa 8 -type crystal structure with space group P 4/mmm. It belongs to the larger family of Ce n T In 3n+2 (T : transition metal, n = 1, 2, and ∞) systems, containing a sequence of n CeIn 3 layers intercalated by a T In 2 layer along the c axis. While cubic CeIn 3 (n = ∞) is a completely isotropic system, the layered structures with n = 1 and 2 are expected to lead to anisotropic properties and quasi-2D FSs. Indeed, quasi-2D FS sheets were observed in both n = 1 systems CeCoIn 5 [19,20] [24,25]. The degree of two dimensionality is expected to be larger in monolayer systems with alternating layers of CeIn 3 and T In 2 than in their bilayer counterparts, in which t...

Specific heat in high magnetic fields and magnetic phase diagram ofCePt2In7

“…While cubic CeIn 3 (n = 1, m = 0) is a completely isotropic system, the layered structures with m = 0 lead to strongly anisotropic properties and quasi-two-dimensional Fermi surfaces. Indeed, quasi-two-dimensional Fermi surface sheets were observed in both monolayer (n = 1, m = 1) systems CeCoIn 5 9,10 , CeIrIn 5 11 , CeRhIn 5 12,13 and bilayer (n = 2, m = 1) compounds Ce 2 RhIn 8 14,15 and Ce 2 PdIn 8 16 . The degree of two dimensionality is expected to increase with increasing the distance between CeIn 3 layers.…”

Fermi-surface topology of the heavy-fermion system Ce2PtIn8

“…This implies that there is a significant mass enhancement due to many-body interactions, which are not included in the LDA calculations. Effective masses much higher than calculated were observed in other non-magnetic HF compounds with itinerant 4f electrons, such as CeCoIn 5 9 and Ce 2 PdIn 8 39 . For the α 1 and α 2 orbits, both lying on the same FS sheet, the mass-enhancement factors are 9.5 and 30, respectively.…”

“…Presumably, this is due to an unfavorable curvature factor. We note, that the calculated frequency branches from band 72 were not observed in the isostructural compound Ce 2 PdIn 8 as well 39 .…”

Quasi-two-dimensional Fermi surfaces with localized f electrons in the layered heavy-fermion compound CePt2In7

“…The reduced dimensionality of the FS is also expected to enhance unconventional superconductivity 13 , which is often observed in HF systems in the vicinity of a QCP. It has been demonstrated experimentally that the FS dimensionality is indeed one of the key parameters determining the superconducting critical temperature in HF materials 14 , so precise knowledge of the topology, particularly the dimensionality, of the FS of HF materials close to a QCP is of primary importance.…”