اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدSimultaneous Superconducting and Antiferroquadrupolar Transitions in PrRh$_{2}$Zn$_{20}$
450
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
Superconducting and antiferroquadrupolar (AFQ) transitions in a Pr-based compound PrRh2Zn20 have been found to occur simultaneously at Tc=TQ=0.06 K. The superconducting transition manifests itself by zero resistance and large diamagnetic susceptibility. The specific heat exhibits a Schottky anomaly peaking at 14 K and magnetization curves measured at 2 K show anisotropic behaviors. The analysis of these data indicates that the crystalline electric field (CEF) ground state of the trivalent Pr ion is the non-Kramers Gamma3 doublet with the quadrupolar degrees of freedom. A sharp peak in the specific heat at 0.06 K has been attributed not to the superconducting transition but to the AFQ transition because the ordering temperature TQ decreases in B || [100] but increases in B || [110] and B || [111] with increasing B up to 6 T. This anisotropic behavior of TQ(B) can be well explained by a two-sublattice mean-field calculation, which corroborates the AFQ ordered state below TQ. The entropy release at TQ is only 10% of Rln2 expected for the Gamma3 doublet, suggesting possible interplay between the quadrupolar degrees of freedom and the superconductivity.
قيم البحث
اقرأ أيضاً
Superconductivity in PrIr$_{2}$Zn$_{20}$ appears at $T_{rm c} = 0.05$ K in the presence of an antiferroquadrupolar order below $T_{rm Q} = 0.11$ K. We have studied pressure dependences of $T_{rm c}$, $T_{rm Q}$, and non-Fermi liquid behaviors in the
resistivity $rho (T)$ by using two pressure transmitting media: argon maintaining highly hydrostatic pressure, and glycerol, which solidifies above 5 GPa producing nonhydrostatic pressure. Upon applying $P$ with argon up to 10.6 GPa, $T_{rm c}$ hardly changes, while $T_{rm Q}$ monotonically increases from 0.11 to 0.23 K. With glycerol, however, $T_{rm Q}$ and $T_{rm c}$ simultaneously fall below 0.04 K at 6.3 GPa. The contrasting results indicate that onsite quadrupolar fluctuations induce superconductivity in this compound.
The results of DC magnetization measurements under hydrostatic (helium-gas) pressure are reported for an ambient pressure superconductor Na0.35CoO2.1.4D2O and its precursor compound, the gamma-phase Na0.75CoO2 that is known to combine a metallic cond
uctivity with an unusual magnetic state below ~22K. The obtained data allowed us to present for the first time the pressure dependence of the magnetic transition in a metallic sodium cobaltate system. This dependence appears to be positive, with the magnetic transition rapidly shifting towards higher temperatures when an applied pressure increases. We ascribe the observed effect to the pressure-induced enhancement of the out-of-plane antiferromagnetic coupling mediated by localized spins interactions (of either superexchange or RKKY type), the scenario consistent with the A-type antiferromagnetic state suggested by recent neutron-scattering data. As for the pressure effect on the superconductivity in Na0.35CoO2.1.4D2O, our measurements established negative and linear for the entire pressure range from 1 bar to 8.3 kbar pressure dependence of Tc, the behavior quite different from the reported by previous workers strong non-linearity of the Tc (P) dependence. (Dated September 12, 2005) PACS numbers: 74.62.Fj, 74.70.-b, 75.20. En, 75.50 Ee, 75.30 Kz.
Ultrafast broadband transient reflectivity experiments are performed to study the interplay between the non-equilibrium dynamics of the pseudogap and the superconducting phases in Bi$_{2}$Sr$_{2}$Ca$_{0.92}$Y$_{0.08}$Cu$_{2}$O$_{8+delta}$. Once super
conductivity is established the relaxation of the pseudogap proceeds $sim$ 2 times faster than in the normal state, and the corresponding transient reflectivity variation changes sign after $sim$ 0.5 ps. The results can be described by a set of coupled differential equations for the pseudogap and for the superconducting order parameter. The sign and strength of the coupling term suggest a remarkably weak competition between the two phases, allowing their coexistence.
Raman scattering experiments on LaFeAsO with splitted antiferromagnetic (T_AFM = 140 K) and tetragonal-orthorhombic (T_S = 155 K) transitions show a quasi-elastic peak (QEP) in B2g symmetry (2 Fe tetragonal cell) that fades away below ~T_AFM and is a
scribed to electronic nematic fluctuations. A scaling of the reported shear modulus with the T-dependence of the QEP height rather than the QEP area indicates that magnetic degrees of freedom drive the structural transition. The large separation between T_S and T_AFM in LaFeAsO compared with their coincidence in BaFe2As2 manifests itself in slower dynamics of nematic fluctuations in the former.
The tilted balance among competing interactions can yield a rich variety of ground states of quantum matter. In most Ce-based heavy fermion systems, this can often be qualitatively described by the famous Doniach phase diagram, owing to the competiti
on between the Kondo screening and the Ruderman-Kittel-Kasuya-Yoshida exchange interaction. Here, we report an unusual pressure-temperature phase diagram beyond the Doniach one in CeCuP2. At ambient pressure, CeCuP2 displays typical heavy-fermion behavior, albeit with a very low carrier density. With lowering temperature, it shows a crossover from a non Fermi liquid to a Fermi liquid at around 2.4 K. But surprisingly, the Kondo coherence temperature decreases with increasing pressure, opposite to that in most Ce-based heavy fermion compounds. Upon further compression, two superconducting phases are revealed. At 48.0 GPa, the transition temperature reaches 6.1 K, the highest among all Ce-based heavy fermion superconductors. We argue for possible roles of valence tuning and fluctuations associated with its special crystal structure in addition to the hybridization effect. These unusual phase diagrams suggest that CeCuP2 is a novel platform for studying the rich heavy fermions physics beyond the conventional Doniach paradigm.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
