Birender Singh

Iron isotope effect in SmFeAsO0.65 and SmFeAsO0.77H0.12 superconductors: A Raman study

We report the inelastic light scattering studies on SmFeAsO0.65 and SmFeAsO0.77H0.12 with iron isotopes namely 54Fe and 57Fe. In both of these systems under investigation we observed a significant shift in the frequency of the phonon modes associated with the displacement of Fe atoms around ∼ 200 cm-1. The observed shift in the Fe mode (B1g) for SmFeAsO0.65 is ∼ 1.4 % and lower in case of SmFeAsO0.77H0.12, which is ∼ 0.65 %, attributed to the lower percentage of isotopic substitution in case of SmFeAsO0.77H0.12. Our study reveals the significant iron isotope effect in these systems hinting towards the crucial role of electron-phonon coupling in the pairing mechanism of iron based superconductors.

Structural and electronic properties of LaPd2As2 superconductor: First-principle calculations

In present work we have studied electronic and structural properties of superconducting LaPd2As2 compound having collapsed tetragonal structure using first-principle calculations. The band structure calculations show that the LaPd2As2 is metallic consistent with the reported experimental observation, and the density of states plots clearly shows that at the Fermi level major contribution to density of states arises from Pd 4d and As 4p states, unlike the Fe-based superconductors where major contribution at the Fermi level comes from Fe 3d states. The estimated value of electron-phonon coupling is found to be ~ 0.37, which gives the upper bound of superconducting transition temperature of ~ 5K, suggesting the conventional nature of this superconductor.

Phonon dynamics in LiZr1.9Al0.1(PO4)3: A temperature dependent Raman study

In this work, we report a detailed temperature dependent inelastic light scattering study on a solid electrolyte LiZr1.9Al0.1(PO4)3 as a function of temperature, from 20 °C to 400 °C, in a wide spectral range of 60 - 1250u2005cm-1. We observed a clear signature of structural phase transition around ∼ 220 °C marked by the renormalization of the phonon frequencies and integrated intensity. The phonon modes frequencies above the transition temperature showed nearly temperature independent behaviour reflecting the disordered nature of the phase transition.In this work, we report a detailed temperature dependent inelastic light scattering study on a solid electrolyte LiZr1.9Al0.1(PO4)3 as a function of temperature, from 20 °C to 400 °C, in a wide spectral range of 60 - 1250u2005cm-1. We observed a clear signature of structural phase transition around ∼ 220 °C marked by the renormalization of the phonon frequencies and integrated intensity. The phonon modes frequencies above the transition temperature showed nearly temperature independent behaviour reflecting the disordered nature of the phase transition.

Density functional study of ACa2Fe4As4F2 (A = K, Rb): Electronic structure, unconventional superconductors

In this work, we have studied the structural and electronic properties of new-type of iron based superconductors ACa2Fe4As4F2 (A = K, Rb) with first principles density functional theory based calcu...

Unconventional iron-based superconductor CsCa2Fe4As4F2: A first-principle study

In the present work, we have investigated the structural and electronic properties of newly discovered iron based superconductor CsCa2Fe4As4F2 using first principles calculations. Analysis of the density of states at the Fermi levelxa0suggests that Fe-3d states have dominating contribution, and within these 3d states contribution of eg states is significantxa0suggesting multi-band nature of this superconductor. The upper bound of superconducting transition temperature, estimated using electron-phonon coupling constant is found to be ∼2.6u2005K. To produce the experimental value of transition temperature (28.2u2005K), a 4-5 times increase in the electron-phonon constant is necessary, hinting that conventional electron-phonon coupling is not enough to explain the origin of superconductivity.