Probing non-equilibrium structural dynamics in low-dimensional and correlated materials using ultrafast diffraction

Novel phenomena arise from the non-equilibrium excitation of materials, and the complex interplay between their various degrees of freedom. Understanding this at a microscopic level requires detailed knowledge about a material’s atomic structure on fast timescales. In this talk, I will discuss the application of ultrafast diffraction techniques to probe structural dynamics in correlated oxides and two-dimensional (2D) materials. First, I will describe a new time-resolved ‘electrical-pump’ technique based on femtosecond electron diffraction, that enables direct measurements of atomic motions in microelectronic devices. In an archetypal correlated oxide, we discover signatures of a transient metastable phase under pulsed electrical bias [1]. Next, I will discuss phonon transport in van der Waals (vdW) heterostructures, which are promising candidates for phononics applications [2]. I will describe our efforts to rationally synthesize ‘3D’ solids with tailored thermal properties using layer-by-layer assembly of 2D crystals. Ultrafast X-ray diffraction is demonstrated as a useful technique to probe heat transport across buried interfaces in vdW stacks [3]. Finally, using ultrafast electron diffraction, I will show how we can interrogate the coupling between charge and lattice dynamics in photoexcited 2D heterostructures, enabling direct observations of heat flow across single vdW junctions on picosecond timescales.

[1] A. Sood et al. in review (2020)
[2] A. Sood*, F. Xiong* et al., Nature Comm. 9, 4510 (2018)
[3] C. Nyby*, A. Sood* et al., Adv. Func. Mater. 30, 2002282 (2020)