اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدDetermination of an onset of superconducting diamagnetism by scaling of the normal-state magnetization
108
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We propose a simple scaling procedure for the normal-state magnetization Mn data collected as functions of temperature T in different magnetic fields H. As a result, the Mn(T) curves collected in different fields collapse on to a single Msc(T) line. In this representation, the onset of superconducting diamagnetism manifests itself by a sharp divergence of the Msc(T) curves for different H values. As will be demonstrated, this allows for a reliable determination of temperature Tonset, at which superconducting diamagnetism become observable.
قيم البحث
اقرأ أيضاً
The recently discovered superconductor, UTe$_2$, has attracted immense scientific interest due to the experimental observations that suggest odd-parity superconductivity. It is believed that the material becomes a heavy-fermion metal at low temperatu
res although details of the normal state are unclear. Using Fourier transform infrared spectroscopy (FTIR), the normal state electronic structure of UTe$_2$ was investigated at zero applied magnetic field. Combining the measured reflectivity with the dc resistivity, the complex optical conductivity was obtained over a large frequency range. The frequency dependence of the real part of the optical conductivity exhibits a MIR peak around 4000 cm$^{-1}$ and a narrow Drude peak that develops below 40 K. A combination of density functional and dynamic mean field theory (DFT + DMFT) gives spectra in close correspondence to the experiment. Via this comparison we attribute the prominent MIR peak to inter-band transitions involving a narrow U 5$f$ feature that develops near the Fermi level. In this regard, our data gives spectroscopic evidence for the existence of a low energy Kondo resonance at temperatures just above the onset of superconductivity and implicates heavy electrons in the formation of the superconducting state. We find that the coherent Kondo resonance is primarily associated with a collapse of scattering and less with a transfer of spectral weight.
We report on muon spin rotation (muSR) studies of the superconducting and magnetic properties of the ternary intermetallic stannide Ca3Ir4Sn13. This material has recently been the focus of intense research activity due to a proposed interplay of ferr
omagnetic spin fluctuations and superconductivity. In the temperature range T=1.6-200 K, we find that the zero-field muon relaxation rate is very low and does not provide evidence for spin fluctuations on the muSR time scale. The field-induced magnetization cannot be attributed to localized magnetic moments. In particular, our muSR data reveal that the anomaly observed in thermal and transport properties at T*~38 K is not of magnetic origin. Results for the transverse-field muon relaxation rate at T=0.02-12 K, suggest that superconductivity emerges out of a normal state that is not of a Fermi-liquid type. This is unusual for an electronic system lacking partially filled f-electron shells. The superconducting state is dominated by a nodeless order parameter with a London penetration depth of lambda=385(1) nm and the electron-phonon pairing interaction is in the strong-coupling limit.
We discuss the analysis of mixed-state magnetization data of type-II superconductors using a recently developed scaling procedure. It is based on the fact that, if the Ginzburg-Landau parameter kappa does not depend on temperature, the magnetic susce
ptibility is a universal function of H/H_c2(T), leading to a simple relation between magnetizations at different temperatures. Although this scaling procedure does not provide absolute values of the upper critical fieldH_c2(T), its temperature variation can be established rather accurately. This provides an opportunity to validate theoretical models that are usually employed for the evaluation of H_c2(T) from equilibrium magnetization data. In the second part of the paper we apply this scaling procedure for a discussion of the notorious first order phase transition in the mixed state of high temperature superconductors. Our analysis, based on experimental magnetization data available in the literature, shows that the shift of the magnetization accross the transition may adopt either sign, depending on the particular chosen sample. We argue that this observation is inconsistent with the interpretation that this transition always represents the melting transition of the vortex lattice.
We compute the two-particle quantities relevant for superconducting correlations in the two-dimensional Hubbard model within the dynamical cluster approximation. In the normal state we identify the parameter regime in density, interaction, and second
-nearest-neighbor hopping strength that maximizes the $d_{x^2-y^2}$ superconducting transition temperature. We find in all cases that the optimal transition temperature occurs at intermediate coupling strength, and is suppressed at strong and weak interaction strengths. Similarly, superconducting fluctuations are strongest at intermediate doping and suppressed towards large doping and half-filling. We find a change in sign of the vertex contributions to $d_{xy}$ superconductivity from repulsive near half filling to attractive at large doping. $p$-wave superconductivity is not found at the parameters we study, and $s$-wave contributions are always repulsive. For negative second-nearest-neighbor hopping the optimal transition temperature shifts towards the electron-doped side in opposition to the van Hove singularity which moves towards hole doping. We surmise that an increase of the local interaction of the electron-doped compounds would increase $T_c$.
We report measurements of the specific heat, Hall effect, upper critical field and resistivity on bulk, B-doped diamond prepared by reacting amorphous B and graphite under high-pressure/high-temperature conditions. These experiments establish unambig
uous evidence for bulk superconductivity and provide a consistent set of materials parameters that favor a conventional, weak coupling electron-phonon interpretation of the superconducting mechanism at high hole doping.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
