The “nickelate family” has been the subject of interest in many studies due to its rich phase diagram, including metal-insulator transitions (MIT), magnetism, and superconductivity in topotactically reduced infinite-layer (IL) compounds and high-temperature superconductivity in Ruddlesden-Popper (RP) phases. Their pronounced structure-property relationship and high tolerance to structural and compositional changes allow tuning of the strength of electronic and magnetic correlations. The recent discovery of high-temperature superconductivity in La3Ni2O7 crystals – under high pressure – has rapidly accelerated the research in this field. By combining extensive STEM imaging and spectroscopy techniques, we are elucidating the fundamental properties of nickelates that exhibit high-temperature superconductivity, metallicity, and metal-insulator transition.

 

Selected Publications

  1. P. Puphal, P. Reiss, N. Enderlein, Y.-M. Wu, G. Khaliullin, V. Sundaramurthy, T. Priessnitz, M. Knauft, L. Richter, M. Isobe, P. A. van Aken, H. Takagi, B. Keimer, Y. E. Suyolcu*, B. Wehinger, P. Hansmann, M. Hepting*; "Unconventional crystal structure of the high-pressure superconductor La3Ni2O7", Physical Reviews Letters 133, 146002, 2024 (Cover Figure, Editor’s Suggestion).
  2. P. Puphal, Y.-M. Wu, K. Fürsich, H. L., M. Pakdaman, J. A. Bruin, J. Nuss, Y. E. Suyolcu, P. A. van Aken, B. Keimer, M. Isobe, M. Hepting*, "Topotactic transformation of single crystals: From perovskite to infinite-layer nickelates", Science Advances 7 (49) 2021.
  3. Y.-M. Wu*, P. Puphal, H. Lee, J. Nuss, M. Isobe, B. Keimer, M. Hepting, Y. E. Suyolcu* and P. A. van Aken; "Topotactically induced oxygen vacancy order in nickelate single-crystals", Physical Review Materials 7 (5), 053609, 2023.
  4. Y.-M. Wu, P. Puphal, M. Isobe, B. Keimer, M. Hepting, Y. E. Suyolcu* and Peter A van Aken; "Unraveling nano-scale effects of topotactic reduction in LaNiO2 crystals", APL Materials 12, 081117, 2024.
  5. S. Hayashida, V. Sundaramurthy, P. Puphal, M. Garcia-Fernandez, Ke-Jin Zhou, B. Fenk, M. Isobe, M. Minola, Y.-M. Wu, Y. E. Suyolcu, P. A. van Aken, B. Keimer*, and M. Hepting; "Investigation of spin excitations and charge order in bulk crystals of the infinite-layer nickelate LaNiO2", Physical Review B. 109, 235106, 2024. (Editor’s Suggestion)
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