Fig. 3

NAQMD simulations of bilayer MoSe₂. a Debye–Waller factor for the MoSe₂ bilayer as a function of delay time for the {110} and {300} planes calculated from NAQMD simulations at carrier density of 0 cm⁻² (black) and 1.2 × 10¹⁴ cm⁻² (red and blue lines). Photoexcitation results in a marked increase in structural disorder and a reduction in the Bragg peak intensity. Exponential fits to the simulations yield a time constant of ~1 ps, as shown in the gray curves. The experimental results shown in circles are the bilayer MoSe₂ at a carrier density of 1.2 × 10¹⁴ cm⁻². Note that there are no normalization factors between the experimental and simulation results. b Instantaneous temperature in the NAQMD simulation cell due to photoexcitation at time t = 0 shows a transient temperature increase from 10 K to 300 K over 1.5 ps. c, d display phonon dispersion curves for the MoSe₂ bilayer at the photoexcited carrier density of c 0 cm⁻², (d) 1.2 × 10¹⁴ cm⁻², respectively. e, f Eigenvectors for the soft acoustic modes at the M-point and K-point, respectively