A team of scientists from the Massachusetts Institute of Technology and the University of Texas at Austin
The method developed by scientists involves the separationone scanning laser pulse into several hundred separate ones. Each of them reaches the test sample at a different time. By measuring the reflected and transmitted waves, and then combining the results of the observations as separate frames, physicists have created a film that gives a microscopic view of the mechanisms through which the transformations occur.
The sample is photoexcited by a laser pulsepumping with an energy of 1.55 eV (vertical beam). With a single reflection, the probing beam with an energy of 1.55 eV (incident from the top left) passes through a set of double 20-step levels and is divided into a 20 by 20 grid of 400 pulses with different time delays. These probe pulses are focused on the sample along with the pump pulse. Reflected probing pulses are detected in different areas of the chamber. Image: Gao et al., Science Advances
In their work, scientists used disulfidetantalum. It consists of covalently bonded layers of tantalum and sulfur atoms loosely stacked on top of each other. Below the critical temperature, the atoms and electrons of this material form nanosized structures - a charge density wave. The formation of this new phase makes the material an insulator, but a single intense light pulse turns it into a metastable hidden metal.
Usually shining a laser on materials is the samethe most that heat them, but not in this case. Here, the irradiation of the crystal rearranges the electronic order, creating a completely new phase, different from the high-temperature one.
Zhuquan Zhang, researcher at the Massachusetts Institute of Technology, co-author of the work
With the help of new technology, scientists have succeeded inobserve the dynamics of this complex phase transformation. They saw that the melting and reordering of the charge density wave leads to the formation of a hidden quantum state.
Physicists believe that understanding the originsuch metastable quantum phases will help to solve fundamental questions of non-equilibrium thermodynamics. Also, while the study was done with one specific material, the scientists say the same methodology can be used to study other exotic phenomena in quantum materials.
Cover image: Frank Yi Gao, MIT
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