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@ARTICLE{Kafle:626185,
      author       = {Kafle, Tika R and Zhang, Yingchao and Wang, Yi-yan and Shi,
                      Xun and Li, Na and Sapkota, Richa and Thurston, Jeremy and
                      You, Wenjing and Gao, Shunye and Dong, Qingxin and
                      Rossnagel, Kai and Chen, Gen-Fu and Freericks, James and
                      Kapteyn, Henry C and Murnane, Margaret M},
      title        = {{N}on-equilibrium states and interactions in the
                      topological insulator and topological crystalline insulator
                      phases of {N}a{C}d$_4${A}s$_3$},
      journal      = {Structural dynamics},
      volume       = {12},
      number       = {1},
      issn         = {2329-7778},
      address      = {Melville, NY},
      publisher    = {AIP Publishing LLC},
      reportid     = {PUBDB-2025-01328},
      pages        = {014501},
      year         = {2025},
      note         = {M.M.M. and H.C.K. acknowledge support by the U.S.Department
                      of Energy, Office of Science, Basic Energy Sciences x-ray
                      Scattering Program Award DE-SC0002002 for this research.The
                      ARPES setup was supported by the NSF through JILA
                      PhysicsFrontiers Center PHY-2317149. J.K.F. was supported by
                      theDepartment of Energy, Basic Energy Sciences under Award
                      DE-FG02-08ER46542. J.K.F. was also supported by the
                      McDevittbequest at Georgetown University.},
      abstract     = {Topological materials are of great interest because they
                      can support metallic edge or surface states that are robust
                      against perturbations, with the potential for technological
                      applications. Here, we experimentally explore the
                      light-induced non-equilibrium properties of two distinct
                      topological phases in NaCd$_4$As$_3$: a topological
                      crystalline insulator (TCI) phase and a topological
                      insulator (TI) phase. This material has surface states that
                      are protected by mirror symmetry in the TCI phase at room
                      temperature, while it undergoes a structural phase
                      transition to a TI phase below 200 K. After exciting the
                      TI phase by an ultrafast laser pulse, we observe a leading
                      band edge shift of >150 meV that slowly builds up and
                      reaches a maximum after ∼0.6 ps and that persists for ∼8
                      ps. The slow rise time of the excited electron population
                      and electron temperature suggests that the electronic and
                      structural orders are strongly coupled in this TI phase. It
                      also suggests that the directly excited electronic states
                      and the probed electronic states are weakly coupled. Both
                      couplings are likely due to a partial relaxation of the
                      lattice distortion, which is known to be associated with the
                      TI phase. In contrast, no distinct excited state is observed
                      in the TCI phase immediately or after photoexcitation, which
                      we attribute to the low density of states and phase space
                      available near the Fermi level. Our results show how
                      ultrafast laser excitation can reveal the distinct excited
                      states and interactions in phase-rich topological
                      materials.},
      cin          = {FS-SXQM},
      ddc          = {500},
      cid          = {I:(DE-H253)FS-SXQM-20190201},
      pnm          = {632 - Materials – Quantum, Complex and Functional
                      Materials (POF4-632)},
      pid          = {G:(DE-HGF)POF4-632},
      experiment   = {EXP:(DE-MLZ)NOSPEC-20140101},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {39935451},
      UT           = {WOS:001416704800003},
      doi          = {10.1063/4.0000273},
      url          = {https://bib-pubdb1.desy.de/record/626185},
}