Investigation of the Influence of Pressure on the Physical Properties and Superconducting Transition Temperature of Chiral Noncentrosymmetric TaRh₂B₂ and NbRh₂B₂

Abstract

TaRh 2 B 2 and NbRh 2 B 2 compounds exhibit noncentrosymmetric superconductivity with a chiral structure. Density functional theory-based ab-initio calculations have been executed to analyze the structural properties, mechanical stability, ductility/ brittleness behaviors, Debye temperature, melting temperature, optical response to incident photon energy, electronic characteristics, and superconducting transition temperature of chiral TaRh 2 B 2 and NbRh 2 B 2 compounds under pressure up to 16 GPa. Both the chiral phases are mechanically stable and exhibit ductile nature under the studied pressure. The maximum value of the Pugh ratio (an indicator of ductile/brittle behaviors) is observed to be 2.55 (for NbRh 2 B 2 ) and 2.52 (for TaRh 2 B 2 ) at 16 GPa. The lowest value of the Pugh ratio is noticed at 0 GPa for both these chiral compounds. The analysis of reflectivity spectra suggests that both the chiral compounds can be used as efficient reflecting materials in the visible energy region. At 0 GPa, the calculated densities of states (DOSs) at the Fermi level are found to be 1.59 and 2.13 states eV −1 per formula unit for TaRh 2 B 2 and NbRh 2 B 2 , respectively. The DOS values of both the chiral phases do not alter significantly with applied pressure. The shape of the DOS curve of both compounds remains almost invariant with applied pressure. The pressure-induced variation of Debye temperatures of both compounds is observed, which may cause the alternation of the superconducting transition temperature, T c , with applied pressure. The probable changing of T c with pressure has been analyzed from the McMillan equation.

Physical properties of newly synthesized noncentrosymmetric TaIr2B2 and NbIr2B2 superconductors: an extensive comparison of GGA and LDA functional investigations

“…This type of behavior of the Ta and Nb analogs was also observed in previous literature studies for the Rh-based NCS compounds, TaRh 2 B 2 and NbRh 2 B 2 . 12,13 The Ta-analog TaIr 2 B 2 also revealed a higher G compared to NbIr 2 B 2 , which indicates that the shear deformation is easier in NbIr 2 B 2 compared to TaIr 2 B 2 . The higher G value of TaIr 2 B 2 is also an indication of its higher hardness nature in comparison with NbIr 2 B 2 .…”

“…The highest values of v are found to be 0.344 for NbIr 2 B 2 and 0.330 for TaIr 2 B 2 using the GGA-PBE functional, which are somewhat higher than those of the Rh-based compounds NbRh 2 B 2 (v = 0.31) and TaRh 2 B 2 (v = 0.30). 12,13 The Vickers hardness (H v ) of the NCS compounds is estimated by the following model from Chen et al:…”

“…Such behavior is also observed in Rh-based NCS superconductors. 12,13 However, an extra absorption peak is observed at ∼35 eV for the NbIr 2 B 2 compound, and then the absorption spectra drop further. This extra absorption peak of NbIr 2 B 2 might be the result of an additional peak of the loss function at around 35 eV of photon energy, as observed in Fig.…”

“…2,3 The NCS superconductors have received enormous attention by the research community due to their unconventional nature of superconductivity with fascinating physical properties. [2][3][4][5][6][7][8][9][10][11][12][13] In 2021, Gao and his coworkers revealed the interesting topological properties in these Ir-based NCS TaIr 2 B 2 and NbIr 2 B 2 compounds. 4 In the normal state, they suggested that these two Ir-based compounds are topological Weyl metals.…”

“…12 These NCS compounds exhibited attractive properties such as their ductile nature, ease of machinability, anisotropic entity, notable values of melting temperature, and prominent reectivity prole. 12,13 To predict the practical application of newly synthesized materials, it is necessary to determine their fundamental physical properties, such as the mechanical performance (ductility/brittleness, hardness, and machinability), melting temperature, and optical properties (optical conductivity, reectivity, optical absorption, dielectric function, and loss function).…”