We have been pioneering the application of RIXS to transient states using x-ray free electron lasers.
Figure 1: An illustration of time-resolved RIXS. See M. P. M. Dean et al., Nature Materials 15, 601–605 (2016) for more details.
Example papers
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Ultrafast dynamics of spin and orbital correlations in quantum materials: an energy-and momentum-resolved perspective
Y Cao,
DG Mazzone,
D Meyers,
JP Hill,
X Liu,
S Wall,
and MPM Dean
Philosophical Transactions of the Royal Society A
377,
20170480
(2019)
[Abs]
[PDF]
[HTML]
[Supp]
Many remarkable properties of quantum materials emerge from states with intricate coupling between the charge, spin and orbital degrees of freedom. Ultrafast photo-excitation of these materials holds great promise for understanding and controlling the properties of these states. Here, we introduce time-resolved resonant inelastic X-ray scattering (tr-RIXS) as a means of measuring the charge, spin and orbital excitations out of equilibrium. These excitations encode the correlations and interactions that determine the detailed properties of the states generated. After outlining the basic principles and instrumentations of tr-RIXS, we review our first observations of transient antiferromagnetic correlations in quasi two dimensions in a photo-excited Mott insulator and present possible future routes of this fast-developing technique. The increasing number of X-ray free electron laser facilities not only enables tackling long-standing fundamental scientific problems, but also promises to unleash novel inelastic X-ray scattering spectroscopies.
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Ultrafast energy and momentum resolved dynamics of magnetic correlations in photo-doped Mott insulator Sr2IrO4
MPM Dean,
Yue Cao,
X Liu,
S Wall,
D Zhu,
Roman Mankowsky,
V Thampy,
XM Chen,
JG Vale,
D Casa,
Jungho Kim,
A. H. Said,
P. Juhas,
R. Alonso-Mori,
J. M. Glownia,
A. Robert,
J. Robinson,
M. Sikorski,
S. Song,
M. Kozina,
H. Lemke,
L. Patthey,
S. Owada,
T. Katayama,
M. Yabashi,
Yoshikazu Tanaka,
T. Togashi,
J. Liu,
C. Rayan Serrao,
B. J. Kim,
L. Huber,
C.-L. Chang,
D. F. McMorrow,
M. Först,
and J. P. Hill
Nature Materials
15,
601–605
(2016)
[Abs]
[HTML]
[arXiv]
[Featured in News and Views]
[BNL Press Release]
Measuring how the magnetic correlations evolve in doped Mott insulators has greatly improved our understanding of the pseudogap, non-Fermi liquids and higherature superconductivity. Recently, photo-excitation has been used to induce similarly exotic states transiently. However, the lack of available probes of magnetic correlations in the time domain hinders our understanding of these photo-induced states and how they could be controlled. Here, we implement magnetic resonant inelastic X-ray scattering at a free-electron laser to directly determine the magnetic dynamics after photo-doping the Mott insulator Sr2IrO4. We find that the non-equilibrium state, 2 ps after the excitation, exhibits strongly suppressed long-range magnetic order, but hosts photo-carriers that induce strong, non-thermal magnetic correlations. These two-dimensional (2D) in-plane Neel correlations recover within a few picoseconds, whereas the three-dimensional (3D) long-range magnetic order restores on a fluence-dependent timescale of a few hundred picoseconds. The marked difference in these two timescales implies that the dimensionality of magnetic correlations is vital for our understanding of ultrafast magnetic dynamics.