Nonlocal Probing of Amplitude Mode Dynamics in Charge-Density-Wave Phase of EuTe4  

作　　者：Ranjana Rathore Himanshu Singhal Vivek Dwij Mayanak K Gupta Abhishek Pathak juzer Ali Chakera Ranjan Mittal Aditya Prasad Roy Arun Babu Ruta Kulkarni A Thamizhavel Ayman H Said Dipanshu Bansal 

机构地区：[1]Laser Plasma Division,Raja Ramanna Centre for Advanced Technology,Indore,MP 452013,India [2]Homi Bhabha National Institute,Training School Complex,Anushaktinagar,Mumbai,MH 400094,India [3]Department of Mechanical Engineering,Indian Institute of Technology Bombay,Mumbai,MH 400076,India [4]Department of Condensed Matter Physics&Materials Science,Tata Institute of Fundamental Research,Mumbai,MH 400005,India [5]Solid State Physics Division,Bhabha Atomic Research Centre,Mumbai,MH 400085,India [6]Advanced Photon Source,Argonne National Laboratory,9700 South Cass Avenue,Lemont,IL 60439,USA [7]Center for Research in Nano Technology and Science,Indian Institute of Technology Bombay,Mumbai,MH 400076,India

出　　处：《Ultrafast Science》2023年第6期25-37,共13页超快科学（英文）

基　　金：D.B.thanks the financial support from the Science&Engineering Research Board(SERB)under project no.CRG/2022/001317,BRNS-DAE under project no.58/14/30/2019-BRNS/11117, MoE/STARS under project no.MoE/STARS-1/345.

摘　　要：Amplitude mode is collective excitation emerging from frozen lattice distortions below the charge-density-wave(CDW)transition temperature TCDW and relates to the order parameter.Generally,the amplitude mode is non-polar(symmetry-even)and does not interact with incoming infrared photons.However,if the amplitude mode is polar(symmetry-odd),it can potentially couple with incoming photons,thus forming a coupled phonon-polariton quasiparticle that can travel with light-like speed beyond the optically excited region.Here,we present the amplitude mode dynamics far beyond the optically excited depth of ∼150 nm in the CDW phase of ∼10-μm-thick single-crystal EuTe4 using time-resolved x-ray diffraction.The observed oscillations of the CDW peak,triggered by photoexcitation,occur at the amplitude mode frequency ωAM.However,the underdamped oscillations and their propagation beyond the optically excited depth are at odds with the observation of the overdamped nature of the amplitude mode measured using meV-resolution inelastic x-ray scattering and polarized Raman scattering.The ωAM is found to decrease with increasing fluence owing to a rise in the sample temperature,which is independently confirmed using polarized Raman scattering and ab-initio molecular dynamics simulations.We rationalize the above observations by explicitly calculating two coupled quasiparticles—phonon-polariton and exciton-polariton.Our data and simulations cannot conclusively confirm or rule out the one but point toward the likely origin from propagating phonon-polariton.The observed non-local behavior of amplitude mode thus provides an opportunity to engineer material properties at a substantially faster time scale with optical pulses.

关 键 词：EXCITED PHONON excitation 

分 类 号：O441[理学—电磁学]