磁场对非寻常超导体小晶体的作用

研究了外磁场作用下的小晶体序参量的各种模式配对破坏效应。对于偶和奇宇称超导体的小晶体，磁场的作用具有定性的差别，并具正常和超态的转变可以是一致的。     

Crystal Electric Field Excitations in the Non-Fermy Liquid Compound YbRh<Subscript>2</Subscript>Si<Subscript>2</Subscript>

We have calculated the crystalline electric field (CEF) splitting of the energy levels of Yb³⁺ (4f¹³) in the clean Yb-based heavy fermion compound YbRh₂Si₂. The data of inelastic neutron scattering and electron spin resonance measurements in YbRh₂Si₂, together with relevant structural, thermodynamic, and magnetic properties, were used as input in the calculations of the possible CEF level scheme in this non-Fermi-liquid compound. Two possible sets of the CEF parameters with the Γ₆ or Γ₇ ground-state symmetry are discussed. PACS: 71.27.+a; 75.20.Hr; 76.30.−v.     

Surface Superconducting State of Heavy-Fermion Superconductor CeIrIn5 Probed by CeIrIn5-Ag Junctions

The CeIrIn₅-Ag junctions of about 2×10^–9 cm^–2 area have been made using microfabrication techniques, and the surface superconducting state of CeIrIn₅, which has two characteristic temperatures T ₀ and T _c, has been investigated, where T ₀ and T _c are the transition temperature to zero-resistivity state and the bulk, thermodynamic transition temperature, respectively. The temperature, below which superconducting anomalies are observed, varies from junction to junction, and yet it is always well above T _c=0.4 K. This result, together with no indication of transition at T _c, suggests that at least the surface of CeIrIn₅ is in the superconducting state above T _c. The data on the critical current I _c in superconducting anomalies point to the possibility to define a local transition temperature for each junction.     

Implications of Tc-Variation in UBe13 for a Possible Fulde–Ferrell–Larkin–Ovchinnikov Phase

We measure the heat capacity of a UBe₁₃ sample with an unusually low T _c for a polycrystal. We find an upturn in the upper critical field H _c2(T) below about T _c/2, much as for higher-T _c samples. Comparing the critical fields in our sample and in samples with higher T _c's shows that the low temperature limit of H _c2 is proportional to T _c(H = 0), as expected if the upturn comes from an FFLO phase and strong coupling.