Nonthermal breaking of magnetic order via photogenerated spin defects in the spin-orbit coupled insulator Sr 3 Ir 2 O 7

Journal Article · 06 February 2022 · Physical Review. B

DOI: https://doi.org/10.1103/physrevb.105.064409 · OSTI ID:1854094

Pastor, Ernest  ^[1]; Moreno-Mencía, David  ^[1]; Monti, Maurizio  ^[2]; Johnson, Allan S.  ^[1]; Fleischmann, Nina ^[3]; Wang, Cuixiang ^[4]; Shi, Youguo ^[4]; Liu, Xuerong ^[5]; Mazzone, Daniel G. ^[6]; Dean, Mark M.  ^[7]; Wall, Simon  ^[3]

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1. Barcelona Institute of Science and Technology (BIST) (Spain)
2. Aarhus Univ. (Denmark)
3. Barcelona Institute of Science and Technology (BIST) (Spain); Aarhus Univ. (Denmark)
4. Chinese Academy of Sciences (CAS), Beijing (China). Inst. of Physics
5. ShanghaiTech Univ. (China)
6. Paul Scherrer Inst. (PSI), Villigen (Switzerland)
7. Brookhaven National Lab. (BNL), Upton, NY (United States). Condensed Matter Physics and Materials Science Dept.

In many strongly correlated insulators, antiferromagnetic order competes with exotic and technologically relevant phases, like superconductivity. While control of spin order is critical to stabilize different functional states, elucidating the mechanism of laser-induced demagnetization in complex oxides remains a challenge. It is unknown if the optical pulse can quench magnetization nonthermally or if it instead only acts as a heat source. In this study, we used ultrafast, broadband, optical spectroscopy to track the responses of the electronic, lattice, and spin degrees of freedom and their relation to antiferromagnetism in the strongly spin-orbit coupled insulator ${\mathrm{Sr}}_3{\mathrm{Ir}}_2{\mathrm{O}}_7$. We find that magnetization can be rapidly and strongly suppressed on a sub-150 fs timescale. At low excitation fluences, the magnetic recovery is fast; however, the recovery time increases dramatically with the magnitude of demagnetization. At the same time, we show that the lattice, evidenced through the $A_g$ phonon frequencies, appears to remain below $T_{\mathrm{N}}$, suggesting that the system remains nonthermal during the optical modulation of spin order. We suggest that photogenerated spin defects are responsible for the long-lived demagnetized state and discuss its implications for optical control of solids.

• Research Organization: Brookhaven National Laboratory (BNL), Upton, NY (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES); European Research Council (ERC); Spanish State Research Agency; National Natural Science Foundation of China (NSFC); K. C. Wong Education Foundation
• Grant/Contract Number: SC0012704
• OSTI ID: 1854094
• Report Number(s): BNL-222842-2022-JAAM
• Journal Information: Physical Review. B, Journal Name: Physical Review. B Journal Issue: 6 Vol. 105; ISSN 2469-9950
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English