On the Intersecting Temperature in Presence of Several Normal State Conduction Mechanisms in High- T c Superconductors
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ORIGINAL PAPER
On the Intersecting Temperature in Presence of Several Normal State Conduction Mechanisms in High-Tc Superconductors I. Mukherjee 1 & Ajay Kumar Ghosh 1 Received: 27 June 2020 / Accepted: 26 September 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract An intersection temperature of the normal state conduction and a state which follows the three-dimensional Aslamazov-Larkin (3DAL) has been studied in several high-temperature superconductors (HTS). Extraction of the coherence length by using the 3DAL equation depends on the existing normal state conduction mechanism. We have used bulk HTS having normal states of different types which can be explained either by using the metallic behavior or the variable range hopping (VRH) conduction. In presence of the several coherence lengths, the shifting of the intersecting point has been studied. Keywords Superconductors . Transport properties . Aslamazov-Larkin . Coherence length
1 Introduction The three-dimensional Aslamazov-Larkin (AL) equation is generally used for the determination of the coherence length in the layered superconducting systems [1–10]. Below the onset transition temperature, there are several characteristic temperatures other than the zero resistive transition temperature. In the broader phase transition, several such characteristic temperatures have been used for the better understanding of the phase transition. In the analysis of the transport properties in hightemperature superconductors (HTS), the mean field transition temperature (Tcmf) is such an important temperature for the determination of coherence length [11, 12]. Normal states can be either metallic or nonmetallic in HTS. If the normal state is extrapolated below the onset transition temperature and the fluctuation region described by 3DAL is extended, there is an intersecting temperature Ti. Around Ti, there is an overlapping of the normal state conduction mechanism and the superconducting fluctuat-
* Ajay Kumar Ghosh [email protected] 1
Department of Physics, Jadavpur University, Kolkata 700032, India
ing state [13, 14]. Even though the overlapping is very narrow in conventional superconductors, it will be comparatively broader in HTS because of its very short coherence length [15]. Understanding the shifting of Ti is therefore an important aspect in explaining the phase transition via any intermediate states in the zero magnetic field. An intersecting temperature has been suggested in the presence of the upturn in resistivity in several cuprate superconductors recently [16]. It has been observed that the coherence length affects the intersecting temperature in case of the normal state following the variable range hopping (VRH) conduction. The intersecting temperature in the presence of the metallic normal state is also an interesting and important subject. Because the coherence length of HTS affects Ti, it will be very important to understand how carrier concentration affects the intersecting temperature. Tuning the carrier
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