Effect of hole doping on superconductivity in compressed <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>CeH</mml:mi><mml:mn>9</mml:mn></mml:msub></mml:math> at high pressures
Chongze Wang, Shuyuan Liu, Hyunsoo Jeon, Seho Yi, Yunkyu Bang, Jun‐Hyung Cho
Abstract
The experimental realization of high-temperature superconductivity in compressed hydrides ${\mathrm{H}}_{3}\mathrm{S}$ and ${\mathrm{LaH}}_{10}$ under high pressures over 150 GPa has aroused great interest in reducing the stabilization pressure of superconducting hydrides. For cerium hydride ${\mathrm{CeH}}_{9}$ recently synthesized at $80--100$ GPa, our first-principles calculations reveal that the strongly hybridized electronic states of $\mathrm{Ce}\text{\ensuremath{-}}4f$ and $\mathrm{H}\text{\ensuremath{-}}1s$ orbitals produce the topologically nontrivial Dirac nodal lines around the Fermi energy ${E}_{F}$, which are protected by crystalline symmetries. By hole doping, ${E}_{F}$ shifts down toward the symmetry-driven van Hove singularity to increase the density of states, which in turn significantly raises a superconducting transition temperature ${T}_{c}$. We show that hole doping with ${\mathrm{Ce}}^{3+}$ ions can be very electronically miscible in ${\mathrm{CeH}}_{9}$ because both ${\mathrm{Ce}}^{3+}$ and Ce behave similarly as cations. Therefore, the interplay of crystalline symmetry, band topology, and hole doping contributes to enhance ${T}_{c}$ in compressed ${\mathrm{CeH}}_{9}$, which can also be demonstrated in another superconducting rare-earth hydride, ${\mathrm{LaH}}_{10}$.