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arXiv · 2409.11894

Origin of the non-Fermi-liquid behavior in CeRh2As2

P. Khanenko·D. Hafner·K. Semeniuk·J. Banda·T. Luehmann·F. Baertl·T. Kotte·J. Wosnitza·G. Zwicknagl·C. Geibel·J. F. Landaeta·S. Khim·E. Hassinger·M. Brando
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Abstract

Unconventional superconductivity in heavy-fermion systems appears often near magnetic quantum critical points (QCPs). This seems to be the case also for CeRh2As2 (Tc $\approx$ 0.31 K). CeRh2As2 shows two superconducting (SC) phases, SC1 and SC2, for a magnetic field along the c axis of the tetragonal unit cell, but only the SC1 phase is observed for a field along the basal plane. Furthermore, another ordered state (phase-I) is observed below T0 $\approx$ 0.48 K whose nature is still unclear: Thermodynamic and magnetic measurements pointed to a non magnetic multipolar state, but recent $μ$SR and NQR/NMR experiments have clearly detected antiferromagnetic (AFM) order below T0 . Also, quasi-two-dimensional AFM fluctuations were observed in NMR and neutron-scattering experiments above T0. The proximity of a QCP is indicated by non-Fermi-liquid (NFL) behavior observed above the ordered states in both specific heat $C(T)/T \propto T^{-0.6}$ and resistivity $ρ(T) \propto T^{0.5}$. These T-dependencies are not compatible with any generic AFM QCP. Because of the strong magnetic-field anisotropy of both the SC phase and phase I, it is possible to study a field-induced SC QCP as well a phase-I QCP by varying the angle $α$ between the field and the c axis. Thus, by examining the behavior of the electronic specific-heat coefficient C(T)/T across these QCPs, we can determine which phase is associated with the NFL behavior. Here, we present low-temperature specific-heat measurements taken in a magnetic field as high as 21 T applied at several angles $α$. We observe that the NFL behavior does very weakly depend on the field and on the angle $α$, a result that is at odd with that observations in standard magnetic QCPs. This suggests a nonmagnetic origin of the quantum critical fluctuations.

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P. Khanenko, D. Hafner, K. Semeniuk, J. Banda, T. Luehmann, F. Baertl, T. Kotte, J. Wosnitza, G. Zwicknagl, C. Geibel, J. F. Landaeta, S. Khim, E. Hassinger, M. Brando. 2024-09-18. Origin of the non-Fermi-liquid behavior in CeRh2As2. https://doi.org/10.1103/physrevb.111.045162

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