Ultrafast lattice disordering can be accelerated by electronic collisional forces

Abstract

In the prevalent picture of ultrafast structural phase transitions, the atomic motion occurs in a slowly varying potential energy surface determined adiabatically by the fast electrons. However, this ignores non-conservative forces caused by electron-lattice collisions, which can significantly influence atomic motion. Most ultrafast techniques only probe the average structure and are less sensitive to random displacements, and therefore do not detect the role played by non-conservative forces in phase transitions. Here we show that the lattice dynamics of the prototypical insulator-to-metal transition of VO2 cannot be described by a potential energy alone. We use the sample temperature to control the preexisting lattice disorder before ultrafast photoexcitation across the phase transition and our ultrafast diffuse scattering experiments show that the fluctuations characteristic of the rutile metal develop equally fast (120 fs) at initial temperatures of 100 K and 300 K. This indicates that additional non-conservative forces are responsible for the increased lattice disorder. These results highlight the need for more sophisticated descriptions of ultrafast phenomena beyond the Born-Oppenheimer approximation as well as ultrafast probes of spatial fluctuations beyond the average unit cell measured by diffraction.

References in corpus (7)

• Evidence for a Structurally-driven Insulator-to-metal Transition in VO2: a View from the Ultrafast Timescale
• Ultrafast changes in lattice symmetry probed by coherent phonons
• How optical excitation controls the structure and properties of vanadium dioxide
• Mapping momentum-dependent electron-phonon coupling and non-equilibrium phonon dynamics with ultrafast electron diffuse scattering
• Langevin dynamics with spatial correlations as a model for electron-phonon coupling
• Uniting the order and disorder dynamics in photoexcited VO2
• Stochastic semiclassical theory for non-equilibrium electron-phonon coupled systems

Cited by in corpus (14)

• Photo-induced nonequilibrium states in Mott insulators
• All-optical seeding of a light-induced phase transition with correlated disorder
• The photoinduced hidden metallic phase of monoclinic VO2 driven by local nucleation via a self-amplification process
• Decoupled few-femtosecond phase transitions in vanadium dioxide
• Picosecond-scale Heterogeneous Melting of Metals at Extreme Non-equilibrium States
• Dynamical decoding of the competition between charge density waves in a kagome superconductor
• Tunable Spatiotemporal Orders in Driven Insulators
• Non-ionizing cross section of electron scattering on atoms in matter accounting for dynamical screening effect
• Light-induced phase transitions in vanadium dioxide: a tensor network study
• Pausing ultrafast melting by timed multiple femtosecond-laser pulses
• Ultrafast surface melting of orbital order in La0.5Sr1.5MnO4
• Local structural disorder in crystalline materials
• Nonequilibrium control of kagome metals
• Ultrafast dynamics of atomic correlated disordering in photoinduced VO${}_2$