Nav: Home

A quasiparticle collider

May 11, 2016

In the early 1900s, Ernest Rutherford shot alpha particles onto gold foils and concluded from their scattering properties that atoms contain their mass in a very small nucleus. A hundred years later, modern scientists took that concept to a new level, building the Large Hadron Collider in Switzerland to smash protons into each other, which led to the discovery of the Higgs boson.

However, what worked for particles like the Higgs hasn't translated to solids -- until now. Experiments conducted by UCSB physicist Mark Sherwin and an international team prove that basic collider concepts from particle physics can be transferred to solid-state research. Their findings appear in the journal Nature.

"Ultimately, this approach might lead to the clarification of some of the most outstanding enigmas of condensed matter physics," said co-author Sherwin, director of UCSB's Institute for Terahertz Science and Technology and a professor in the Department of Physics. "This is a fundamentally new concept that could lead to better-designed modern materials. Our results also may one day provide a better understanding of important phases of matter such as those found in high-temperature superconductors."

Despite the fact that modern technology depends on knowing the structural and electronic properties of solids, a parallel to the atomic-level collider has been lacking in solid-state research. Within a solid, the most useful analogs to particles like protons are called quasiparticles. Think of them this way: If each person in a very large stadium is like an atom in a solid, then the audience doing the "wave" is akin to a quasiparticle.

Earlier experiments by the Sherwin group at UCSB have created quasiparticles called excitons -- pairs of electrons and holes (electron vacancies) bound by the electrical force between them -- and continuously accelerated them using laser beams that remain on during the entire process. But without short pulses of laser light, actual collision events were not previously observable as distinct flashes of light.

This new research employed a unique laser source at the terahertz high-field lab in Regensburg, Germany, which enabled the investigators to directly observe quasiparticle collision events. Since the quasiparticle exists for an extremely short amount of time, it was crucial to operate on ultrashort timescales. If one second were stretched to the age of the universe, a quasiparticle would only exist for a few hours.

The scientists produced collisions within excitons in a thin flake of tungsten diselenide. A light wave of the terahertz pulse accelerated the electrons and holes of the exciton within a period shorter than a single oscillation of light (1 terahertz means 1 trillion oscillations per second).

The experiment demonstrates that only excitons created at the right time lead to electron-hole collisions, just as in conventional accelerators. However, this process of recollision generates ultrashort light bursts that encode key aspects of the solid. These laboratory observations have been supported and explained by a quantum mechanical simulation performed by co-authors at the University of Marburg in Germany.

"These time-resolved collision experiments in a solid prove that the basic collider concepts that have transformed our understanding of the subatomic world can be transferred from particle physics to solid-state research," Sherwin said. "They also shed new light on quasiparticles and many-body excitations in condensed matter systems."

University of California - Santa Barbara

Related Physics Articles:

Physics vs. asthma
A research team from the MIPT Center for Molecular Mechanisms of Aging and Age-Related Diseases has collaborated with colleagues from the U.S., Canada, France, and Germany to determine the spatial structure of the CysLT1 receptor.
2D topological physics from shaking a 1D wire
Published in Physical Review X, this new study propose a realistic scheme to observe a 'cold-atomic quantum Hall effect.'
Helping physics teachers who don't know physics
A shortage of high school physics teachers has led to teachers with little-to-no training taking over physics classrooms, reports show.
Physics at the edge
In 2005, condensed matter physicists Charles Kane and Eugene Mele considered the fate of graphene at low temperatures.
Using physics to print living tissue
3D printers can be used to make a variety of useful objects by building up a shape, layer by layer.
More Physics News and Physics Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Erasing The Stigma
Many of us either cope with mental illness or know someone who does. But we still have a hard time talking about it. This hour, TED speakers explore ways to push past — and even erase — the stigma. Guests include musician and comedian Jordan Raskopoulos, neuroscientist and psychiatrist Thomas Insel, psychiatrist Dixon Chibanda, anxiety and depression researcher Olivia Remes, and entrepreneur Sangu Delle.
Now Playing: Science for the People

#537 Science Journalism, Hold the Hype
Everyone's seen a piece of science getting over-exaggerated in the media. Most people would be quick to blame journalists and big media for getting in wrong. In many cases, you'd be right. But there's other sources of hype in science journalism. and one of them can be found in the humble, and little-known press release. We're talking with Chris Chambers about doing science about science journalism, and where the hype creeps in. Related links: The association between exaggeration in health related science news and academic press releases: retrospective observational study Claims of causality in health news: a randomised trial This...