Ultrafast charge localization in a stripe-phase nickelate

• Published in: Nature communications Vol. 4; no. 1; p. 2643
• Main Authors: Coslovich, G., Huber, B., Lee, W. -S., Chuang, Y. -D., Zhu, Y., Sasagawa, T., Hussain, Z., Bechtel, H. A., Martin, M. C., Shen, Z. -X., Schoenlein, R. W., Kaindl, R. A.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 24-10-2013; Nature Publishing Group; Nature Pub. Group
• Subjects: 140/125; 639/766/119; 639/766/400; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Correlated electron materials, Charge stripes, Mid-Infrared Spectroscopy, Ultrafast Science; Humanities and Social Sciences; MATERIALS SCIENCE; multidisciplinary; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms3643

Self-organized electronically ordered phases are a recurring feature in correlated materials, resulting in, for example, fluctuating charge stripes whose role in high-
T
C
superconductivity is under debate. However, the relevant cause–effect relations between real-space charge correlations and low-energy excitations remain hidden in time-averaged studies. Here we reveal ultrafast charge localization and lattice vibrational coupling as dynamic precursors of stripe formation in the model compound La
1.75
Sr
0.25
NiO
4
, using ultrafast and equilibrium mid-infrared spectroscopy. The opening of a pseudogap at a crossover temperature
T
*
far above long-range stripe formation establishes the onset of electronic localization, which is accompanied by an enhanced Fano asymmetry of Ni-O stretch vibrations. Ultrafast excitation triggers a sub-picosecond dynamics exposing the synchronous modulation of electron–phonon coupling and charge localization. These results illuminate the role of localization in forming the pseudogap in nickelates, opening a path to understanding this mysterious phase in a broad class of complex oxides.
In correlated materials, a universal yet elusive feature is the occurrence of self-organized electronically ordered phases. Using equilibrium and pump–probe spectroscopy of a nickelate, the authors reveal ultrafast charge localization and vibrational coupling as precursors of a charge-stripe phase.