Optical spectroscopy and ultrafast pump-probe study of the structural phase transition in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mn>1</mml:mn><mml:msup><mml:mi>T</mml:mi><mml:mo>′</mml:mo></mml:msup><mml:mo>−</mml:mo><mml:msub><mml:mi mathvariant="normal">TaTe</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>
Tianchen Hu, Qiong Wu, Z. X. Wang, L. Y. Shi, Q. M. Liu, Li Yue, S. J. Zhang, Rongsheng Li, Xinyu Zhou, Shaolong Xu, Dong Wu, Tao Dong, Nanlin Wang
Abstract
$1{T}^{\ensuremath{'}}\text{\ensuremath{-}}\mathrm{Ta}{\mathrm{Te}}_{2}$ exhibits an intriguing first-order structural phase transition at around 170 K. Understanding the electronic structural properties is a crucial way to comprehend the origin of this structural phase transition. We performed a combined optical and ultrafast pump-probe study on the compound across the transition temperature. The phase transition leads to abrupt changes in both optical spectra and ultrafast electronic relaxation dynamics. The measurements revealed a sudden reconstruction of the band structure. We elaborate that the phase transition is of first order and cannot be attributed to a conventional density-wave type instability. Our work is illuminating for understanding the origin of the structural phase transition.