Physicists have done something that has remained elusive until now. By working on tantalum disulfide, they were able to see the hidden quantum phase of the substance. This achievement could translate into building quantum computers and optoelectronic technologies.
Thanks to the development of powerful high-speed photography in the 1960s by Prof. Harold “Doc” Edgerton allowed us to visualize events very fast to the eye. We can see a bullet piercing an apple or a drop hitting a pond. Using a similar set of tools, Scientists at the Massachusetts Institute of Technology The University of Texas at Austin went one step further. They captured a light-induced snapshot of an unstable phase viewed in real time. Details are described in the magazine science progress.
Usually, the luminosity of the laser on the material is the same as heating it, but not in this case. Here, the crystal irradiation rearranges the electronic system, creating a completely new phase, different from the high temperature phase.Zhuquan Zhang of the Massachusetts Institute of Technology
Understanding the origins of these unstable quantum phases is important to solve long-standing fundamental questions in thermodynamics.
Key to this result was the development of a modern laser method that can record videos of irreversible processes in quantum materials with a time resolution of 100 femtoseconds.Eduardo Baldini of the Massachusetts Institute of Technology
Unusual manipulations of light
Tantalum disulfide consists of covalently bonded layers of tantalum and sulfur atoms arranged loosely on top of each other. Below the critical temperature, the material’s atoms and electrons were formed on a “Star of David” nanoscale – an unconventional electronic distribution known as a “charge density wave”.
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Creating a new phase makes the material an insulator, but it is enough to apply light to it to turn it into a hidden, stable metal.
It is a quantum transient frozen in time. Humans have observed this previously hidden light-induced phase, but the ultrafast quantum processes behind its origin are still unknown.Eduardo Baldini
Physicists have been able to come up with an innovative way of splitting a single laser pulse into several hundred smaller pulses that arrive at the sample at different times before and after the start of the measurement. Based on the measurements, the film provides insight into the mechanisms by which changes occur in the material.
Although the study was conducted on only one material – tantalum disulfide – the same methodology can be used to study other exotic phenomena in quantum materials. The discovery could also aid the development of on-demand photoelectronic devices.
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