ترغب بنشر مسار تعليمي؟ اضغط هنا

Evolution of Paramagnetic Quasiparticle Excitations Emerged in the High-Field Superconducting Phase of CeCoIn5

187   0   0.0 ( 0 )
 نشر من قبل Yuji Matsuda
 تاريخ النشر 2011
  مجال البحث فيزياء
والبحث باللغة English




اسأل ChatGPT حول البحث

We present In NMR measurements in a novel thermodynamic phase of CeCoIn5 in high magnetic field, where exotic superconductivity coexists with the incommensurate spin-density wave order. We show that the NMR spectra in this phase provide direct evidence for the emergence of the spatially distributed normal quasiparticle regions. The quantitative analysis for the field evolution of the paramagnetic magnetization and newly-emerged low-energy quasiparticle density of states is consistent with the nodal plane formation, which is characterized by an order parameter in the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state. The NMR spectra also suggest that the spatially uniform spin-density wave is induced in the FFLO phase.



قيم البحث

اقرأ أيضاً

We report on a study of thermal Hall conductivity k_xy in the superconducting state of CeCoIn_5. The scaling relation and the density of states of the delocalized quasiparticles, both obtained from k_xy, are consistent with d-wave superconducting sym metry. The onset of superconductivity is accompanied by a steep increase in the thermal Hall angle, pointing to a striking enhancement in the quasiparticle mean free path. This enhancement is drastically suppressed in a very weak magnetic field. These results highlight that CeCoIn_5 is unique among superconductors. A small Fermi energy, a large superconducting gap, a short coherence length, and a long mean free path all indicate that CeCoIn_5 is clearly in the superclean regime (E_F/Delta<<l/xi), in which peculiar vortex state is expected.
In the heavily hole-doped iron-based superconductors $A$Fe$_2$As$_2$ ($A=$ K, Rb, and Cs), the electron effective mass increases rapidly with alkali-ion radius. To study how the mass enhancement affects the superconducting state, we measure the Londo n penetration depth $lambda(T)$ in clean crystals of $A$Fe$_2$As$_2$ down to low temperature $Tsim0.1$ K. In all systems, the superfluid stiffness $rho_s(T)=lambda^2(0)/lambda^2(T)$ can be approximated by a power-law $T$ dependence at low temperatures, indicating the robustness of strong momentum anisotropy in the superconducting gap $Delta(k)$. The power $alpha$ increases from $sim1$ with mass enhancement and approaches an unconventional exponent $alphasim 1.5$ in the heaviest CsFe$_2$As$_2$. This appears to be a hallmark of superconductors near antiferromagnetic quantum critical points, where the quasiparticles excited across the anisotropic $Delta(k)$ are significantly influenced by the momentum dependence of quantum critical fluctuations.
Superconducting (SC) gap symmetry and magnetic response of cubic U0.97Th0.03Be13 are studied by means of high-precision heat-capacity and dc magnetization measurements using a single crystal, in order to address the long-standing question of its seco nd phase transition at Tc2 in the SC state below Tc1. The absence (presence) of an anomaly at Tc2 in the field-cooling (zero-field-cooling) magnetization indicates that this transition is between two different SC states. There is a qualitative difference in the field variation of the transition temperatures; Tc2(H) is isotropic whereas Tc1(H) exhibits a weak anisotropy between [001] and [111] directions. In the low temperature phase below Tc2(H), the angle-resolved heat-capacity $C(T,H, phi)$ reveals that the gap is fully opened over the Fermi surface, narrowing down the possible gap symmetry.
Using small-angle neutron scattering, we have studied the flux-line lattice (FLL) in superconducting CeCoIn5. The FLL is found to undergo a first-order symmetry and reorientation transition at ~0.55 T at 50 mK. The FLL form factor in this material is found to be independent of the applied magnetic field, in striking contrast to the exponential decrease usually observed in superconductors. This result is consistent with a strongly field-dependent coherence length in CeCoIn5, in agreement with recent theoretical predictions for superclean, high-kappa superconductors.
101 - Nan Zhou , Yue Sun , C. Y. Xi 2021
When exposed to high magnetic fields, certain materials manifest an exotic superconducting (SC) phase that attracts considerable attention. A proposed explanation of the origin of the high-field phase is the Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) sta te. This state is characterized by inhomogeneous superconductivity, where the Cooper pairs have finite center-of-mass momenta. Recently, the high-field phase has been observed in FeSe, and it was deemed to originate from the FFLO state. Here, we synthesized FeSe single crystals with different levels of disorders. The level of disorder is expressed by the ratio of the mean free path to the coherence length and ranges between 35 and 1.2. The upper critical field $B_{rm{c}2}$ was systematically studied over a wide range of temperatures, which went as low as $sim$ 0.5 K, and magnetic fields, which went up to $sim$ 38 T along the $c$ axis and in the $ab$ plane. In the high-field region parallel to the $ab$ plane, an unusual SC phase was confirmed in all the crystals, and the phase was found to be robust to disorders. This result suggests that the high-filed SC state in FeSe may not be a FFLO state, which should be sensitive to disorders.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا