Unconventional superconductivity differs from the conventional one by the pairing mechanism. In conventional or s wave superconductor electrons with opposite spin and momentum form cooper pair and superconductivity occurs as a result of electron phonon interaction. In the unconventional superconductor pairing mechanism is different than that of conventional one , for example p wave pairing where electrons with similar direction of spin forms the cooper pair. Unconventional superconductivity has been observed in systems such as heavy fermion,cuprates, iron based superconductors etc. In recent years topological superconductivity has gained attention due to the combination of topological states in the band sturucture and occurance of superconductivity simultaneously. The much studied PbTaSe2 is one of the topological superconductor which has been found to host nodal line in the band structure and superconductivity ocuurs at 3.72K .Theoretically predicted the structure ABSe2 is topological superconductor where A denotes the intercalate metal(Pb,Sn or In) and B is the transition metal(Nb or Ta). This thesis aims at exploring superconductivity in these systems. We have grown single crystals of SnxNbSe2 and polycrystals of InNbSe2, PbNbSe2 and SnTaSe2 .The transport properties of SnxNbse2 has been measured to gain insight on the superconductivity of this systems. Two samples with varied Sn concentration have been measured and found to superconduct around 5K(sample1) and 8K(sample2). In the conventional superconductor the upper critical field follows the WWH curve . Our samples have shown to contradict this behaviour . The upper critical field of sample1 exceeded than that of sample2.The anisotropy is larger in sample1 than in the sample2. This might imply unconventional pairing mechanism in these systems. In this theis we introduce the aspects of topological superconductivity in Chapter 1. Chapter 2 describes the sample growth and experimental technique. The characterisation of various samples through XRD and EDS have been described in Chapter 3 . On Chapter 4 we discuss the transport properties of samples through resistivity measurement . The upper critical field of these samples and possible pairing mechanism has been described in Chapter 5
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Doctor of Philosophy (Ph.D.)
College of Sciences
Length of Campus-only Access
Doctoral Dissertation (Campus-only Access)
Munir, Riffat, "Unusual Superconductivity in Topological nodal Line Semimetal" (2021). Electronic Theses and Dissertations, 2020-. 533.