Metallic crossover through the tilt-free transition in La 3 Ni 2 O 7 at high pressure and temperature

Abstract

La3Ni2O7, a bilayer nickelate with Ruddlesden-Popper structure, undergoes a pressure-induced structural transition from a tilted Amam phase to an untilted Fmmm (or I4/mmm) phase near 10-15 GPa, concomitant with the emergence of high-Tc superconductivity (Tc ∼ 80 K). Despite intense interest, the phase boundaries and the impact of structural changes on the electronic properties remain unclear. Here, we combine high-pressure and high-temperature Raman and synchrotron-based infrared spectroscopies to map the structural and electronic evolutions. Raman measurements confirm the pressure-driven structural transition and reveal the emergence of Fano line shapes, indicating enhanced electron-phonon coupling. High-temperature data show analogous spectral signatures above 544 K, suggesting an upper temperature limit of the Amam phase within the T-P phase diagram of this system. Infrared reflectivity measurements evidence a concomitant enhanced metallicity, with a tremendous two-order-of-magnitude increase in carrier density, marking a crossover from a weakly to highly metallic state. These results establish a unified picture of the structural transition and its strong coupling to the electronic properties.

Versions

Metallic crossover through the tilt-free transition in La 3 Ni 2 O 7 at high pressure and temperaturePublished versionPhysical Review B · 10.1103/832c-p7qj

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BibTeX RIS

BibTeX

@article{michon2026metallic,
  title = {{Metallic crossover through the tilt-free transition in La 3 Ni 2 O 7 at high pressure and temperature}},
  author = {Bastien Michon and Yingpeng Yu and Beatrice d'Alò and Elena Stellino and Gergely Németh and Bosen Wang and Jianping Sun and Jinguang Cheng and Paolo Postorino and Ferenc Borondics and Francesco Capitani},
  journal = {Physical Review B},
  year = {2026},
  month = sep,
  doi = {10.1103/832c-p7qj},
  eprint = {2605.01651},
  archivePrefix = {arXiv},
  url = {https://hal.science/hal-05795506v1},
  note = {CC BY 4.0},
}

RIS

TY  - JOUR
TI  - Metallic crossover through the tilt-free transition in La 3 Ni 2 O 7 at high pressure and temperature
AU  - Bastien Michon
AU  - Yingpeng Yu
AU  - Beatrice d'Alò
AU  - Elena Stellino
AU  - Gergely Németh
AU  - Bosen Wang
AU  - Jianping Sun
AU  - Jinguang Cheng
AU  - Paolo Postorino
AU  - Ferenc Borondics
AU  - Francesco Capitani
PY  - 2026
DA  - 2026/09/01
JO  - Physical Review B
DO  - 10.1103/832c-p7qj
UR  - https://hal.science/hal-05795506v1
AB  - La3Ni2O7, a bilayer nickelate with Ruddlesden-Popper structure, undergoes a pressure-induced structural transition from a tilted Amam phase to an untilted Fmmm (or I4/mmm) phase near 10-15 GPa, concomitant with the emergence of high-Tc superconductivity (Tc ∼ 80 K). Despite intense interest, the phase boundaries and the impact of structural changes on the electronic properties remain unclear. Here, we combine high-pressure and high-temperature Raman and synchrotron-based infrared spectroscopies to map the structural and electronic evolutions. Raman measurements confirm the pressure-driven structural transition and reveal the emergence of Fano line shapes, indicating enhanced electron-phonon coupling. High-temperature data show analogous spectral signatures above 544 K, suggesting an upper temperature limit of the Amam phase within the T-P phase diagram of this system. Infrared reflectivity measurements evidence a concomitant enhanced metallicity, with a tremendous two-order-of-magnitude increase in carrier density, marking a crossover from a weakly to highly metallic state. These results establish a unified picture of the structural transition and its strong coupling to the electronic properties.
SN  - 2469-9950
SN  - 2469-9969
ER  -

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