Relation between Crystal Structure and Transition Temperature of Superconducting Metals and Alloys

Michael Rudolf Koblischka,Masato Murakami,Xian Lin Zeng,Susanne Roth,Stefanos Fasoulas,Alex Wiederhold,Anjela Koblischka-Veneva,Thomas Karwoth

doi:10.3390/met10020158

Michael Rudolf Koblischka, Masato Murakami + Show 6 more

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https://doi.org/10.3390/met10020158

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Abstract

Using the Roeser–Huber equation, which was originally developed for high temperature superconductors (HTSc) (H. Roeser et al., Acta Astronautica 62 (2008) 733), we present a calculation of the superconducting transition temperatures, T c , of some elements with fcc unit cells (Pb, Al), some elements with bcc unit cells (Nb, V), Sn with a tetragonal unit cell and several simple metallic alloys (NbN, NbTi, the A15 compounds and MgB 2 ). All calculations used only the crystallographic information and available data of the electronic configuration of the constituents. The model itself is based on viewing superconductivity as a resonance effect, and the superconducting charge carriers moving through the crystal interact with a typical crystal distance, x. It is found that all calculated T c -data fall within a narrow error margin on a straight line when plotting ( 2 x ) 2 vs. 1 / T c like in the case for HTSc. Furthermore, we discuss the problems when obtaining data for T c from the literature or from experiments, which are needed for comparison with the calculated data. The T c -data presented here agree reasonably well with the literature data.

Highlights

In 1908, Dutch physicist Heike Kamerlingh Onnes succeeded in liquefying helium 4 He, which extended the lowest temperature achievable in a laboratory from 14 K [1] to slightly belowIn the following years, more and more superconductors have been found, first in pure metals and later in alloys and compounds
The breakthrough came with the discovery of superconductivity in a ceramic material containing lanthanum (La), barium (Ba), copper (Cu) and oxygen (O) with the full formula La2− x Bax CuO4 (LBCO), with a critical temperature around 30 K by Bednorz and Müller in 1986 [6]
As the charge carriers in the metallic superconductors are always Cooper pairs formed by electrons or by holes, we introduce here the abbreviation, ML, not to be confused with Meff used in the band structure calculations

Summary

Introduction

More and more superconductors have been found, first in pure metals and later in alloys and compounds. With 9.2 K, the highest critical temperature observed in a natural element belongs to niobium (Nb). Before 1950, this critical temperature was the highest of all superconducting materials until the alloy NbN0.96 was found to superconduct at 15.2 K, and in 1954, the A15-structured compound Nb3 Sn broke the record with 18.1 K [4]. It became clear that practical applications would require the discovery of materials that will become superconducting at significantly higher temperatures. The breakthrough came with the discovery of superconductivity in a ceramic material containing lanthanum (La), barium (Ba), copper (Cu) and oxygen (O) with the full formula La2− x Bax CuO4

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