title: Photoinduced Enhancement of the Charge Density Wave Amplitude.
abstract: Symmetry breaking and the emergence of order is one of the most fascinating phenomena in condensed matter physics. It leads to a plethora of intriguing ground states found in antiferromagnets, Mott insulators, superconductors, and density-wave systems. Exploiting states of matter far from equilibrium can provide even more striking routes to symmetry-lowered, ordered states. Here, we demonstrate for the case of elemental chromium that moderate ultrafast photoexcitation can transiently enhance the charge-density-wave (CDW) amplitude by up to 30% above its equilibrium value, while strong excitations lead to an oscillating, large-amplitude CDW state that persists above the equilibrium transition temperature. Both effects result from dynamic electron-phonon interactions, providing an efficient mechanism to selectively transform a broad excitation of the electronic order into a well-defined, long-lived coherent lattice vibration. This mechanism may be exploited to transiently enhance order parameters in other systems with coupled degrees of freedom.
authors: Department of Physics, University of California-San Diego, La Jolla, California 92093, USA.
authors: A
authors: A
authors: Singer
authors: Department of Physics, University of California-San Diego, La Jolla, California 92093, USA.|Center for Memory and Recording Research, University of California-San Diego, La Jolla, California 92093, USA.
authors: S K K
authors: SK
authors: Patel
authors: Department of Physics, University of California-San Diego, La Jolla, California 92093, USA.|Center for Memory and Recording Research, University of California-San Diego, La Jolla, California 92093, USA.
authors: R
authors: R
authors: Kukreja
authors: Center for Memory and Recording Research, University of California-San Diego, La Jolla, California 92093, USA.
authors: V
authors: V
authors: Uhlíř
authors: Department of Physics, University of California-San Diego, La Jolla, California 92093, USA.
authors: J
authors: J
authors: Wingert
authors: Institute for Experimental and Applied Physics, Kiel University, 24098 Kiel, Germany.
authors: S
authors: S
authors: Festersen
authors: LCLS, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors: D
authors: D
authors: Zhu
authors: LCLS, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors: J M
authors: JM
authors: Glownia
authors: LCLS, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors: H T
authors: HT
authors: Lemke
authors: LCLS, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors: S
authors: S
authors: Nelson
authors: LCLS, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors: M
authors: M
authors: Kozina
authors: Institute for Experimental and Applied Physics, Kiel University, 24098 Kiel, Germany.
authors: K
authors: K
authors: Rossnagel
authors: Institute for Experimental and Applied Physics, Kiel University, 24098 Kiel, Germany.
authors: M
authors: M
authors: Bauer
authors: Institute for Experimental and Applied Physics, Kiel University, 24098 Kiel, Germany.|Ruprecht Haensel Laboratory, Kiel University, 24098 Kiel, Germany.
authors: B M
authors: BM
authors: Murphy
authors: Institute for Experimental and Applied Physics, Kiel University, 24098 Kiel, Germany.|Ruprecht Haensel Laboratory, Kiel University, 24098 Kiel, Germany.
authors: O M
authors: OM
authors: Magnussen
authors: Center for Memory and Recording Research, University of California-San Diego, La Jolla, California 92093, USA.
authors: E E
authors: EE
authors: Fullerton
authors: Department of Physics, University of California-San Diego, La Jolla, California 92093, USA.
authors: O G
authors: OG
authors: Shpyrko