Electrons losing weight

May 1, 2017

The measured mass of electrons in solids is always larger than the value predicted by theory. The reason for this is that theoretical calculations do not account properly for various interactions with other electrons or lattice vibrations – that "dress" the electrons. EPFL scientists have now carried out a study on a lithium-containing copper oxide and have found that its electrons are 2.5 times lighter than was predicted by theoretical calculations. The work is published in Physical Review Letters and has made the cover.

The lab of Marco Grioni at EPFL used a spectroscopy technique called ARPES (), which allows researchers to "track" electron behavior in a solid material. In this case, the solid material was a copper oxide, a member of the transition-metal oxide family of materials, which have wide-ranging applications for their electronic, magnetic and catalytic properties. In this type of copper oxide Cu atoms have two different values of valence, making it a "mixed-valence" compound.

The researchers used ARPES to measure the energy of the electron bands in the copper oxide. This then helped them calculate the mass of its . Simply put, the broader the band, the smaller the electron's mass.

Running the measurements, the scientists found that the 's electrons are actually 2.5 times lighter than the values given by theoretical predictions. "This is rather unique and unexpected," says Marco Grioni. "It goes against a widely accepted tenet of many-body theory that says that correlation effects generally yield narrower bands and larger electron masses."

The authors state that present-day electronic structure calculation techniques may provide an intrinsically inappropriate description of ligand-to-d hybridizations in late transition metal oxides.

Explore further: Prediction of superconductivity in compounds based on iridium oxide opens a new chapter for superconductors

More information: S. Moser et al. Electronic Phase Separation and Dramatic Inverse Band Renormalization in the Mixed-Valence Cuprate, Physical Review Letters (2017). DOI: 10.1103/PhysRevLett.118.176404

Related Stories

Measuring time without a clock

February 8, 2017

EPFL scientists have been able to measure the ultrashort time delay in electron photoemission without using a clock. The discovery has important implications for fundamental research and cutting-edge technology.

Elusive metal discovered

August 22, 2012

Carnegie scientists are the first to discover the conditions under which nickel oxide can turn into an electricity-conducting metal. Nickel oxide is one of the first compounds to be studied for its electronic properties, ...

Recommended for you

On the rebound

January 22, 2018

Our bodies have a remarkable ability to heal from broken ankles or dislocated wrists. Now, a new study has shown that some nanoparticles can also "self-heal" after experiencing intense strain, once that strain is removed.

Nanoparticle gel controls twisted light with magnetism

January 22, 2018

"Help me, Obi Wan Kenobi. You're my only hope." For many of those around at the release of Star Wars in 1977, that scene was a first introduction to holograms—a real technology that had been around for roughly 15 years.

Information engine operates with nearly perfect efficiency

January 19, 2018

Physicists have experimentally demonstrated an information engine—a device that converts information into work—with an efficiency that exceeds the conventional second law of thermodynamics. Instead, the engine's efficiency ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.