Hun-ho Kim's doctoral dissertation "Uniaxial pressure study of charge density waves in a high-Tc cuprate superconductor" was selected for the Springer Thesis Award, which implies publication in book form in the Springer Theses
series. Hun-ho Kim had graduated with distinction from the University of Stuttgart in 2020.In this thesis work, Hun-ho Kim performed an elegant series of resonant and non-resonant x-ray scattering experiments on the high-temperature superconductor YBa2
under highly homogeneous uniaxial pressure and demonstrated the power of this method to modulate the interplay between superconducting and charge-density-wave (CDW) phases without introducing disorder and inhomogeneity. Specifically, he showed that uniaxial pressure enhances short-range-ordered CDWs in the copper-oxide planes and confirmed that the underlying order parameter is uniaxial, thus conclusively resolving a long-standing debate (H.H. Kim et al., Phys. Rev. Lett. 126, 037002 (2021)
). He also discovered a three-dimensionally long-range ordered CDW that competes strongly against superconductivity, and showed that it is induced by softening of an optical phonon, in close analogy to classical structural phase transitions (H.H. Kim, M. Souliou et al., Science 362, 6418, 1040-1044 (2018)
) His work on uniaxial pressure tuning opens up many new perspectives for research on high-temperature superconductors and other quantum materials.