Charge Density Waves and Superconductivity in Rare Earth Compounds from First Principles

High-temperature superconductivity at ambient pressures has been a major goal in condensed matter physics for decades. For conventional superconductors, strong electron-phonon coupling and high frequency phonons are the key ingredients to realizing this. However, strong electron-phonon coupling also leads to charge density waves and structural distortions which compete with superconductivity. To better understand this competition, I use first-principles simulations to study rare-earth tritellurides (RTe3) and doped rare-earth trihydrides (RH3), which host superconducting states when their charge-density-waves/structural transitions are suppressed. I develop useful computational tools for this purpose and find that the effects of strong correlation (captured with DFT+U simulations) has a nontrivial effect on the susceptibility of these materials to structural distortions. In doped rare earth trihydrides, nuclear quantum effects are found to stabilize the system against structural distortions and allow superconducting temperatures to reach above 120 K. We benchmark Tc estimation methods and use them for larger supercells which indicate Tc's up to 220 K may be possible in the doped RH3 system.