Pressure induced evolution of anisotropic superconductivity and Fermi surface nesting in a ternary boride

Abstract: Using Migdal-Eliashberg theory implemented in Electron Phonon Wannier (EPW) code, we have investigated anisotropic superconductivity of a ternary boride $\mathrm{Ta(MoB)_2}$. The robust coupling between $\mathrm{\sigma}$-bonding states, primarily created by the d-orbitals of Mo atoms and the in-plane vibrations of Mo atoms, facilitates the generation of cooper pairs that make $\mathrm{Ta(MoB)_2}$ a single-gap anisotropic superconductor with a critical temperature ($\mathrm{T_c}\sim ) \, 19.3$ K. A weak Fermi surface nesting and the low value of electron-phonon coupling cannot induce charge density wave instabilities, as evidenced by the lack of a significant peak in the real part of total Lindhard susceptibility and the absence of phonon softening. Furthermore, the system is readily tunable by hydrostatic pressure up to 76.69 GPa, owing to its low bulk modulus and negative formation energy. The persistent reduction in the density of states at the Fermi level, Fermi nesting and the stiffening of phonon modes leads to a diminution of superconductivity under pressure up to 59.71 GPa. At 76.69 GPa, a modification in the topology of the Fermi surface, namely a Lifshitz transition, occurs resulting in a sudden improvement in the nesting condition. This enhanced nesting, in turn, induces an abrupt stabilisation of superconductivity at 76.69 GPa, resulting in a V-shaped response to pressure.