Pressure-induced superconductivity in an antiferromagnet CeRh2Si2

Abstract

We studied the pressure effect by measuring the electrical resistivity for a high-quality single crystal of an antiferromagnet CeRh 2 Si 2 with the tetragonal structure. The Néel temperature becomes zero around 1 GPa. An onset of superconductivity appears below 0.5 K in a relatively wide pressure region from 0.97 to 1.20 GPa, while the resistivity zero, which appears below 0.4 K, is found to be located in an extremely narrow region from 1.03 to 1.08 GPa. Correspondingly the A value of the Fermi liquid relation in the electrical resistivity (ρ = ρ 0 +AT 2 ) becomes maximum around 1 GPa. Superconductivity is realized in a heavy fermion state.The f electrons of cerium and uranium compounds exhibit a variety of characteristics including spin and valence fluctuations, heavy fermions, Kondo insulators and anisotropic superconductivity [1]. Recently, a new aspect of these compounds with magnetic ordering has been discovered. When pressure P is applied to the cerium compounds with antiferromagnetic ordering such as CeIn 3 , CePd 2 Si 2 [2], CeCu 2 Ge 2 [3] and CeRhIn 5 [4], the Néel temperature T N → 0 is reached at the quantum critical pressure P c . Superconductivity and/or the non-Fermi liquid nature are observed around P c . Very recently superconductivity was also found in a ferromagnetic state in UGe 2 [5] and URhGe [6]. The crossover from the magnetic ordered state to the non-magnetic state under pressure, crossing the quantum critical point, is the most interesting issue in strongly correlated f-electron systems.CeRh 2 Si 2 crystallizes in the tetragonal ThCr 2 Si 2 -type structure and orders antiferromagnetically below the Néel temperature T N1 = 36 K at ambient pressure. Its magnetic structure was investigated by the neutron diffraction measurements [7]. Below T N1 , the propagation

Fermi surface instabilities inCeRh2Si2at high magnetic field and pressure

“…1 in good agreement with previous measurements 5,7,13,14 . S(T ) and S(T )/T at low temperature for different pressures are represented in figure 3b) and c) respectively.…”

“…Up to now, the CeRu 2 Si 2 series is the fingerprint example of these phenomena 2,3 . Here we present the effects of H an P on the thermoelectric power (TEP) of the compound CeRh 2 Si 2 with the aim to observe the response on a system where a FS instability under pressure is well established by previous de Haas van Alphen (dHvA) experiments [4][5][6] and where the magnetic structure of the AF phase has been fully determined 7 . Figure 1 represents the main features of the CeRh 2 Si 2 (H, T , P ) phase diagram as measured from our TEP.…”

Non-centrosymmetric Heavy-Fermion Superconductors

“…Assuming that magnetic fluctuations stabilize the superconducting phase and become stronger at the QCP, P * 3 should be regarded as a virtual QCP. In the vicinity of the QCP some pressure-induced HF superconductors display a strong enhancement of the effective mass of the conduction electrons; namely, via the γ n value and the coefficient A of the T 2 term of the electrical resistivity [79,80,81]. In the cases of CeRhSi 3 and CeIrSi 3 , however, such an enhancement is less obvious.…”

Commensurate and incommensurate spin-density waves in heavy electron systems

“…This leads to a superconducting phase of the S + type above the QCP. Superconducting domes of this type have been observed in CeRh 2 Si 2 , 16,17 CePd 2 Si 2 and CeIn 3 18,19 under pressure. Due to the competition between the SDW and the S + order the dome is split into two regions, 9 one with a pure S + phase and the other with coexisting S + and SDW, in agreement with NMR experiments for CeIn 3 , 20 for CeCu 2 (Si 0.98 Ge 0.02 ) 2 , 21 and CeRhIn 5 .…”