Picosecond Laser Provides New Insights to Elicit Useful Electronic Properties in Materials

6 months ago by Luke James

Researchers in Canada have used laser pulses to record, frame-by-frame, how electrons react with atomic vibrations in solids. This could reveal new superconductivity mechanisms that may shed light on previously unknown properties of quantum materials.

As recently published in Science, researchers from the Stewart Blusson Quantum Matter Institute (SBQMI) at the University of British Columbia in Canada have developed a new extreme-ultraviolet (EUV) laser source to enable a technique known as time-resolved photoemission spectroscopy. 

This technique visualizes how electrons are scattered from atoms in solid materials at ultrafast timescales and could provide new insights into superconductivity. 

 

Ultrafast laser used on fluctuating copper pairs.

A laser used in a previous experiment conducted by the (UBC) University of British Columbia on superconductivity research development in the scientific community. Image Credit: UBC Science.

 

Time-resolved Photoemission Spectroscopy

It is the electron-phonon coupling in solids that is responsible for macroscopic quantum properties such as superconductivity—the set of physical properties in certain materials where electrical resistance vanishes and from which magnetic flux fields are expelled. Superconductors are used to make extremely powerful electromagnets to accelerated charged particles. 

However, measuring this electron-phonon coupling as a function is difficult.  

As such, spectroscopies have become an important tool for making clear the microscopic description and dynamic properties of quantum materials. By tracking the dynamics of nonthermal electrons, the dominant scattering processes of a material can be revealed.  

Time-resolved photoemission spectroscopy techniques are a new tool for the investigation of scattering processes in complex quantum materials. 

“Using an ultrashort laser pulse, we excited individual electrons away from their usual equilibrium environment,” said MengXing Na, a PhD student at SBQMI. “Using a second laser pulse as an effective camera shutter, we captured how the electrons scatter with surrounding atoms on timescales faster than a trillionth of a second. Owing to the very high sensitivity of our setup, we were able to measure directly—for the first time—how the excited electrons interacted with a specific atomic vibration, or phonon.”

The Canadian research team performed their experiments using graphite and a laser facility developed by Arthur Mills, one of the Science paper’s co-authors.

David Jones, an SBQMI professor, said, “Thanks to recent advances in pulsed-laser sources, we’re only just beginning to visualize the dynamic properties of quantum materials,”.

By applying these new techniques, the Canadian team is on track to reveal new information surrounding high-temperature superconductivity and many other properties of quantum matter. If the team is able to identify dominant microscopic interactions that define a material’s properties, they “can find ways to ‘turn up’ or ‘down’ the interaction to elicit useful electronic properties”, said Na. 

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