Nav: Home

Chirality yields colossal photocurrent

March 04, 2019

Chestnut Hill, Mass. (3/4/2019) - A recently discovered Weyl semimetal delivers the largest intrinsic conversion of light to electricity of any material, an international team lead by a group of Boston College researchers reports today in the journal Nature Materials.

The discovery is based on a unique aspect of the material where electrons can be separated by their chirality, or handedness -- similar to DNA. The findings may offer a new route to efficient generation of electricity from light, as well as for thermal or chemical sensing. 

"We discovered that the Weyl semimetal Tantalum Arsenide, has a colossal bulk photovoltaic effect - an intrinsic, or non-linear, generation of current from light more than ten times larger than ever previously achieved," said Boston College Associate Professor of Physics Kenneth Burch, a lead author of the article, titled "Colossal mid-infrared bulk photovoltaic effect in a type-I Weyl semimetal."

"Furthermore this is in the mid-infrared regime, which means this material can also be used for chemical or thermal sensing, as well as waste heat recovery," Burch added.

Typically, light is converted to electricity by creating a built-in electric field in a semiconductor, Burch said. "This is achieved through chemical modulation, and results in a fundamental upper limit to the potential efficiency - known as the Shockley-Queisser limit."

The alternative approach taken by the team explored exploiting the handedness of the electrons in the material to intrinsically generate direct current through the nonlinear mixing of the waves of light, Burch said.

This approach has typically been too small to be useful. But researchers recently realized it is closely connected to the topological properties of the electrons. That prompted predictions that the unique, DNA-like behavior of electrons in Weyl semimetals could produce enormous nonlinear effects.

"We focused on answering whether Weyl semimetals live up to the predictions of large, intrinsic nonlinear responses to generate current," said Burch, co-author of the paper with Philip Moll of Ecole Polytechnique Federale de Lausanne, and Ni Ni of UCLA.

He added that the team was surprised at the magnitude of the electronic effect, which was provoked by a new fabrication approach.

"The size of the effect was far larger than we dreamed," said Burch. "A previous group from MIT found their response was dominated by thermal, or extrinsic, terms, our use of the focused ion beam fabricated devices and symmetry allowed us to uncover the colossal bulk photovoltaic effect at room temperature."

Burch said the team is working to determine the "sweet spot" for the effect, specifically what is the ideal device configuration and wavelength of light.
-end-


Boston College

Related Electrons Articles:

Deceleration of runaway electrons paves the way for fusion power
Fusion power has the potential to provide clean and safe energy that is free from carbon dioxide emissions.
Shining light on low-energy electrons
The classic method for studying how electrons interact with matter is by analyzing their scattering through thin layers of a known substance.
Ultrafast nanophotonics: Turmoil in sluggish electrons' existence
An international team of physicists has monitored the scattering behavior of electrons in a non-conducting material in real-time.
NASA mission uncovers a dance of electrons in space
NASA's MMS mission studies how electrons spiral and dive around the planet in a complex dance dictated by the magnetic and electric fields, and a new study revealed a bizarre new type of motion exhibited by these electrons.
'Hot' electrons don't mind the gap
Rice University scientists discover that 'hot' electrons can create a photovoltage about a thousand times larger than ordinary temperature differences in nanoscale gaps in gold wires.
Electrons used to control ultrashort laser pulses
We may soon get better insight into the microcosm and the world of electrons.
Supercool electrons
Study of electron movement on helium may impact the future of quantum computing.
Two electrons go on a quantum walk and end up in a qudit
There is a variety of physical systems that can be used to implement a separate quantum bit, but significantly less research has been done into systems of several qubits or qudits.
Radiation that knocks electrons out and down, one after another
Researchers at Japan's Tohoku University are investigating novel ways by which electrons are knocked out of matter.
Controlling electrons in time and space
A new method has been developed to control electrons being emitted from metal tips.

Related Electrons Reading:

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

Digital Manipulation
Technology has reshaped our lives in amazing ways. But at what cost? This hour, TED speakers reveal how what we see, read, believe — even how we vote — can be manipulated by the technology we use. Guests include journalist Carole Cadwalladr, consumer advocate Finn Myrstad, writer and marketing professor Scott Galloway, behavioral designer Nir Eyal, and computer graphics researcher Doug Roble.
Now Playing: Science for the People

#529 Do You Really Want to Find Out Who's Your Daddy?
At least some of you by now have probably spit into a tube and mailed it off to find out who your closest relatives are, where you might be from, and what terrible diseases might await you. But what exactly did you find out? And what did you give away? In this live panel at Awesome Con we bring in science writer Tina Saey to talk about all her DNA testing, and bioethicist Debra Mathews, to determine whether Tina should have done it at all. Related links: What FamilyTreeDNA sharing genetic data with police means for you Crime solvers embraced...