Three-dimensional ultrafast electron and phonon dynamics in CuTe

Recently, low-dimensional materials have been the subject of many studies because they feature an unusual quantum state of charge density waves (CDWs), which renders them suited to applications in switchable electronics. However, there is no complete CDW phase diagram in three dimensions (3D), and the phase transition mechanism is currently moot. This study demonstrates the first detection and calculation of various-dimensional CDW phases in CuTe using the distinct temperature evolution of orientation-dependent ultrafast pump-probe spectroscopy. At T=280 K, electron-phonon coupling creates 1D collective modes along the a-axis and further synchronizes via an interchain interaction to establish a 2D CDW phase on the ab-plane while T<250 K. The 2D CDW phase planes are finally locked with each other in anti-phase to form a 3D CDW phase at temperatures of less than 220 K. This study shows the dimension evolution of CDW phases in one quantum system and their stabilized mechanisms in different temperature regimes.