Ahmad, Tarek Mohamed Fayez
(2013)
Determination Of Energy Gap Of The Iron-Based Oxypnictide And Laofege Superconductors Using Specific Heat Capacity.
PhD thesis, Universiti Sains Malaysia.
Abstract
The most prominent indicators of superconductivity are the superconducting transition temperature (Tc) and the superconducting energy gap (Δ). These indicators associated with electronic state of temperature dependence of resistivity and specific heat measurements, respectively. The specific heat is a bulk measurement that reflects the behavior of the entire sample response. Here, we introduce a model that examines the transition characteristic to a normal/superconducting state at a critical temperature of the electron and phonon contributions of specific heat. Three basic postulates were adopted. First is that the transition of the system from normal to superconducting state, which allows phonons to bind electrons to form Cooper pairs, requiring a change in energy differences appearing in a specific heat behavior. Second, specific heat has different contributions, changing differently at Tc. This change is possibly a result of the physical function on such contributions. The third postulate is that phonon behavior can manifest superconductive property, particularly in the coexisting state.
Based on the suggested superconducting transition model, which was constructed depending on the superconductive behavior of specific heat in accordance with above postulates, energy scales were obtained at normal state for iron-based oxypnictides. The pseudogap 2Δ was 14.26 meV for the SmO0.80F0.20FeAs compound, which was determined from the far-infrared reflectance spectra based on the phonon state at room temperature.
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