Emergent States in Photoinduced Charge-Density-Wave Transitions

Speaker:  Alfred Zong, MIT

Program Description:
Upon excitation with an intense laser pulse, a symmetry-broken ground state can undergo a non-equilibrium phase transition through pathways different from those in thermal equilibrium. In this talk, we will explore the dynamics under this non-adiabatic regime in charge-density-wave (CDW) compounds, which serve as a model system with long-range order. Using a suite of time-resolved probes – electron diffraction, photoemission, and optical spectroscopy – we find that topological defects play a central role in the evolution of the order parameter [1], whose dynamics exhibits critical behavior near the phase boundary [2]. Remarkably, light can manipulate defects to form metastable structures [3] and unleash a competing CDW order that is absent in equilibrium [4].

[1] Zong*, Kogar* et al. Nat. Phys. 15, 27 (2019)

[2] Zong et al. Phys. Rev. Lett. 123, 097601 (2019)

[3] Zong*, Shen* et al. Sci. Adv. 4, eaau5501 (2018)

[4] Kogar*, Zong* et al. Nat. Phys. in press (2019) [arXiv:1904.07472]