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Title: Lattice-mediated magnetic order melting in TbMnO 3

Recent ultrafast magnetic-sensitive measurements have revealed a delayed melting of the long-range cycloid spin order in TbMnO 3 following photoexcitation across the fundamental Mott-Hubbard gap. The microscopic mechanism behind this slow transfer of energy from the photoexcited carriers to the spin degrees of freedom is still elusive and not understood. Here, we address this problem by combining spectroscopic ellipsometry, ultrafast broadband optical spectroscopy, and ab initio calculations. Upon photoexcitation, we observe the emergence of a complex collective response, which is due to high-energy coherent optical phonons coupled to the out-of-equilibrium charge density. This response precedes the magnetic order melting and is interpreted as the fingerprint of the formation of anti-Jahn-Teller polarons. We propose that the charge localization in a long-lived self-trapped state hinders the emission of magnons and other spin-flip mechanisms, causing the energy transfer from the charge to the spin system to be mediated by the reorganization of the lattice. In conclusion, we provide evidence for the coherent excitation of a phonon mode associated with the ferroelectric phase transition.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ; ORCiD logo [6] ;  [3] ;  [2] ;  [7]
  1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
  2. Eidgenossische Technische Hochschule (ETH) Zurich, Zurich (Switzerland)
  3. Univ. of Fribourg, Fribourg (Switzerland)
  4. Hunan Univ., Changsha (China)
  5. Johns Hopkins Univ., Baltimore, MD (United States)
  6. Brookhaven National Lab. (BNL), Upton, NY (United States)
  7. Ecole Polytechnique Federale Lausanne (Switzlerland)
Publication Date:
Report Number(s):
BNL-205704-2018-JAAM
Journal ID: ISSN 2469-9950; PRBMDO
Grant/Contract Number:
SC0012704; FG02-08ER46544
Type:
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 97; Journal Issue: 12; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
OSTI Identifier:
1439296
Alternate Identifier(s):
OSTI ID: 1429944

Baldini, Edoardo, Kubacka, Teresa, Mallett, Benjamin P. P., Ma, Chao, Koohpayeh, Seyed M., Zhu, Yimei, Bernhard, Christian, Johnson, Steven L., and Carbone, Fabrizio. Lattice-mediated magnetic order melting in TbMnO3. United States: N. p., Web. doi:10.1103/PhysRevB.97.125149.
Baldini, Edoardo, Kubacka, Teresa, Mallett, Benjamin P. P., Ma, Chao, Koohpayeh, Seyed M., Zhu, Yimei, Bernhard, Christian, Johnson, Steven L., & Carbone, Fabrizio. Lattice-mediated magnetic order melting in TbMnO3. United States. doi:10.1103/PhysRevB.97.125149.
Baldini, Edoardo, Kubacka, Teresa, Mallett, Benjamin P. P., Ma, Chao, Koohpayeh, Seyed M., Zhu, Yimei, Bernhard, Christian, Johnson, Steven L., and Carbone, Fabrizio. 2018. "Lattice-mediated magnetic order melting in TbMnO3". United States. doi:10.1103/PhysRevB.97.125149.
@article{osti_1439296,
title = {Lattice-mediated magnetic order melting in TbMnO3},
author = {Baldini, Edoardo and Kubacka, Teresa and Mallett, Benjamin P. P. and Ma, Chao and Koohpayeh, Seyed M. and Zhu, Yimei and Bernhard, Christian and Johnson, Steven L. and Carbone, Fabrizio},
abstractNote = {Recent ultrafast magnetic-sensitive measurements have revealed a delayed melting of the long-range cycloid spin order in TbMnO3 following photoexcitation across the fundamental Mott-Hubbard gap. The microscopic mechanism behind this slow transfer of energy from the photoexcited carriers to the spin degrees of freedom is still elusive and not understood. Here, we address this problem by combining spectroscopic ellipsometry, ultrafast broadband optical spectroscopy, and ab initio calculations. Upon photoexcitation, we observe the emergence of a complex collective response, which is due to high-energy coherent optical phonons coupled to the out-of-equilibrium charge density. This response precedes the magnetic order melting and is interpreted as the fingerprint of the formation of anti-Jahn-Teller polarons. We propose that the charge localization in a long-lived self-trapped state hinders the emission of magnons and other spin-flip mechanisms, causing the energy transfer from the charge to the spin system to be mediated by the reorganization of the lattice. In conclusion, we provide evidence for the coherent excitation of a phonon mode associated with the ferroelectric phase transition.},
doi = {10.1103/PhysRevB.97.125149},
journal = {Physical Review B},
number = 12,
volume = 97,
place = {United States},
year = {2018},
month = {3}
}