Grüner, Density Waves in Solids, Frontiers in Physics (Īddison-Wesley Pub. Specifically, CDWs constitute a periodic modulation of the charge density by electron–hole pairing, 12 12. Co., Advanced Book Program, Reading, MA, 1994), Vol. On the theory of superconductivity: The one-dimensional case,” Proc. Springer Science & Business Media, 2012).Įlectron–lattice interaction is an important source of symmetry breaking in solids, most prominently in superconductivity and the formation of charge-density wave (CDW) phases. Auerbach, Interacting Electrons and Quantum Magnetism ( Moreover, the degenerate ground state of such systems allows for non-trivial topological states, as in the case of magnetic vortices. Goldstone, “įield theories with superconductor solutions,” Il Nuovo Cimento 19, 154– 164 (1961). Quasi-particles and gauge invariance in the theory of superconductivity,” Phys. and massless Nambu–Goldstone bosons, 7,8 7. Higgs, “īroken symmetries and the masses of gauge bosons,” Phys. An essential consequence of this symmetry breaking is the emergence of new amplitude and phase excitations of the fields considered, exemplified in the Higgs mechanism 6 6. Simons, Condensed Matter Field Theory (Ĭambridge University Press, 2010). Springer Science & Business Media, 2012). Zurek, “Ĭosmological experiments in superfluid helium?,” Nature 317, 505– 508 (1985). Topology of cosmic domains and strings,” J. Weinberg, The Quantum Theory of Fields (Ĭambridge University Press, 1995). The spontaneous breaking of a continuous symmetry is a fundamental concept of physics with broad relevance in such diverse areas as particle physics, 1 1. Finally, a broadening of the superlattice peaks is observed at high fluences, pointing to a non-linear generation of phase fluctuations. The long-lived non-equilibrium order parameter suppression suggests hot populations of CDW-coupled lattice modes. This delayed return to a quasi-thermal level is controlled by lattice thermalization and coincides with the population of zone-center acoustic modes, as evidenced by a structured diffuse background. Fluence-dependent relaxation cycles reveal a long-lived partial suppression of the order parameter for up to 60 ps, far outlasting the initial amplitude recovery and electron-phonon scattering times. Comparing distinct groups of diffraction peaks, we disentangle the ultrafast quench of the PLD amplitude from phonon-related reductions of the diffraction intensity. Sequential structural relaxation processes are observed by tracking the intensities of main lattice as well as satellite diffraction peaks and the diffuse scattering background. Employing ultrafast low-energy electron diffraction with 1 ps temporal resolution, we investigate the ultrafast quench and recovery of the CDW-coupled periodic lattice distortion (PLD). We study the non-equilibrium structural dynamics of the incommensurate and nearly commensurate charge-density wave (CDW) phases in 1 T- TaS 2.
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