title: Coherent optical phonon oscillation and possible electronic softening in WTe2 crystals.
abstract: A rapidly-growing interest in WTe2 has been triggered by the giant magnetoresistance effect discovered in this unique system. While many efforts have been made towards uncovering the electron- and spin-relevant mechanisms, the role of lattice vibration remains poorly understood. Here, we study the coherent vibrational dynamics in WTe2 crystals by using ultrafast pump-probe spectroscopy. The oscillation signal in time domain in WTe2 has been ascribed as due to the coherent dynamics of the lowest energy A1 optical phonons with polarization- and wavelength-dependent measurements. With increasing temperature, the phonon energy decreases due to anharmonic decay of the optical phonons into acoustic phonons. Moreover, a significant drop (15%) of the phonon energy with increasing pump power is observed which is possibly caused by the lattice anharmonicity induced by electronic excitation and phonon-phonon interaction.
authors.affiliation: National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China.
authors.forename: Bin
authors.initials: B
authors.lastname: He
authors.affiliation: National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China.|Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
authors.forename: Chunfeng
authors.initials: C
authors.lastname: Zhang
authors.affiliation: National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China.
authors.forename: Weida
authors.initials: W
authors.lastname: Zhu
authors.affiliation: National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China.
authors.forename: Yufeng
authors.initials: Y
authors.lastname: Li
authors.affiliation: National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China.
authors.forename: Shenghua
authors.initials: S
authors.lastname: Liu
authors.affiliation: National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China.
authors.forename: Xiyu
authors.initials: X
authors.lastname: Zhu
authors.affiliation: National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China.
authors.forename: Xuewei
authors.initials: X
authors.lastname: Wu
authors.affiliation: National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China.
authors.forename: Xiaoyong
authors.initials: X
authors.lastname: Wang
authors.affiliation: National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China.
authors.forename: Hai-Hu
authors.initials: HH
authors.lastname: Wen
authors.affiliation: National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China.|Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.|Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701, United States.
authors.forename: Min
authors.initials: M
authors.lastname: Xiao