QMC Colloquium: Mariano Trigo - SLAC National Accelerator Laboratory
- Calendar
- Department of Physics Calendar
- Date
- Oct 15, 2026 2:00pm - 3:00pm
- Location
- 1410 John S. Toll Bldg
Description
Transient textured phases uncovered by ultrafast x-ray scattering
Ultrafast optical excitation can drive materials into novel states that cannot be accesed in equilibrium. Visualizing the pathways of transformation into those states can inspire rational ways to control materials’ functionality. In this talk will show two examples where femtosecond x-ray scattering at free-electron lasers (XFELs) uncovers hidden and transient orders.
First, strong terahertz (THz) pulses induce transient ferroelectricity in the quantum paraelectric SrTiO3, yet equilibrium studies hint at a hidden phase with spatially modulated polarization. Our results on THz-driven diffuse X-ray scattering uncovers hybrid polaracoustic modes that soften at wavelengths of tens of nanometers, precursors of an incipient phase with spatially modulated polarization [1]. Furthermore, under only moderate uniaxial strain a new amplitude mode emerges at finite wavevector while the crystal remains inversion-symmetric on long length scales, the signature of a strain-stabilized phase with nanoscale polar texture. This hints at unstrained SrTiO3 being the disordered side of this transition rather than a conventional incipient ferroelectric.
Second, fast non-adiabatic passage through a phase transition generates topological defects that govern the return to equilibrium, as well as phase competition, yet their dynamics have remained elusive. After strong photoexcitation of the incommensurate charge density waves (CDW) in SmTe3 and LaTe3, we directly observe the creation and evolution of such defects [2]. Scaling and self-similarity of the intensity identifies them as vortex strings, i.e. dislocations of the CDW. I will discuss the impact of these defects in the long-term stability of a competing CDW order recently observed in LaTe3.Â
Together, these results highlight momentum-resolved ultrafast probes as an incisive tool for uncovering hidden transient orders in quantum materials.
References
[1] G. Orenstein et al., Nat. Phys. 21, 961 (2025).
[2] G. Orenstein et al., Phys. Rev. X 15, 031058 (2025).
Host: Sternbach
Ultrafast optical excitation can drive materials into novel states that cannot be accesed in equilibrium. Visualizing the pathways of transformation into those states can inspire rational ways to control materials’ functionality. In this talk will show two examples where femtosecond x-ray scattering at free-electron lasers (XFELs) uncovers hidden and transient orders.
First, strong terahertz (THz) pulses induce transient ferroelectricity in the quantum paraelectric SrTiO3, yet equilibrium studies hint at a hidden phase with spatially modulated polarization. Our results on THz-driven diffuse X-ray scattering uncovers hybrid polaracoustic modes that soften at wavelengths of tens of nanometers, precursors of an incipient phase with spatially modulated polarization [1]. Furthermore, under only moderate uniaxial strain a new amplitude mode emerges at finite wavevector while the crystal remains inversion-symmetric on long length scales, the signature of a strain-stabilized phase with nanoscale polar texture. This hints at unstrained SrTiO3 being the disordered side of this transition rather than a conventional incipient ferroelectric.
Second, fast non-adiabatic passage through a phase transition generates topological defects that govern the return to equilibrium, as well as phase competition, yet their dynamics have remained elusive. After strong photoexcitation of the incommensurate charge density waves (CDW) in SmTe3 and LaTe3, we directly observe the creation and evolution of such defects [2]. Scaling and self-similarity of the intensity identifies them as vortex strings, i.e. dislocations of the CDW. I will discuss the impact of these defects in the long-term stability of a competing CDW order recently observed in LaTe3.Â
Together, these results highlight momentum-resolved ultrafast probes as an incisive tool for uncovering hidden transient orders in quantum materials.
References
[1] G. Orenstein et al., Nat. Phys. 21, 961 (2025).
[2] G. Orenstein et al., Phys. Rev. X 15, 031058 (2025).
Host: Sternbach