Physicists solve a 140-year-old mystery

Scientists discover the inner workings of an effect that will lead to a new generation of devices.

Carrier-resolved photo-Hall effect.

Credit: IBM
  • Researchers discover a method of extracting previously unavailable information from superconductors.
  • The study builds on a 19th-century discovery by physicist Edward Hall.
  • The research promises to lead to a new generation of semiconductor materials and devices.


New research, led by IBM, made a breakthrough in resolving a mystery that has baffled physicists for 140 years. It promises to lead to a new generation of semiconductor materials and devices that use them.

The invention of semiconductors was instrumental in bringing on our digital age. You can find these electricity-carrying substances in your smartphone and computer. An improvement in this field could have major ramifications for future gadgetry.

In 1879, the American physicist Edward Hall discovered the Hall effect, showing that you can measure how electricity in a conductor flows. He found that because a magnetic field deflects the movement of electronic charges in a conductor, you can measure the amount of that deflection. This number will describe the voltage perpendicular (or transverse) to the flow of charge.

Modern researchers recognized, that you can also make Hall effect measurements using light in so-called photo-Hall experiments that generate multiple carriers (or electron-hole pairs) in superconductors. Unfortunately, while the Hall voltage provides crucial information about these charge carriers in a semiconductor, it is limited to the properties of the dominant (or majority) charge carrier, explain contributing authors Oki Gunawan and Doug Bishop in a post on IBM's research blog.

Figuring out the information about both the majority and minority charge carriers, which impact changes in conductivity, would be key to advancing applications utilizing light, including optoelectronic devices like solar cells, LEDs, and lasers as well as artificial intelligence tech.

Now a new formula and technique for getting both the majority and minority carrier information was developed by researchers from KAIST (Korea Advanced Institute of Science and Technology), KRICT (Korea Research Institute of Chemical Technology), Duke University, and IBM.

The method, dubbed Carrier-Resolved Photo Hall (CRPH), measurement, can simultaneously extract information about the majority and minority carriers like density and mobility, carrier lifetimes and lengths of diffusion. In fact, compared to the three parameters of measurement traditionally derived by engaging the Hall effect, the novel technique can get up to seven parameters of information.

Credit: Gunawan/Nature magazine

The approach also takes advantage of a tool developed by IBM called the parallel dipole line (PDL) trap, which generates an oscillating magnetic field. It works as an ideal system for photo-Hall experiments because of the large amount of space it allocates for sample illumination.

If you'd like to dive more into the subject, check out the new study published in Nature magazine.

Higher ed isn’t immune to COVID-19, but the crisis will make it stronger

The pandemic reminds us that our higher education system, with all its flaws, remains a key part of our strategic reserve.

Sponsored by Charles Koch Foundation
  • America's higher education system is under great scrutiny as it adapts to a remote-learning world. These criticisms will only make higher ed more innovative.
  • While there are flaws in the system and great challenges ahead, higher education has adapted quickly to allow students to continue learning. John Katzman, CEO of online learning organization Noodle Partners, believes this is cause for optimism not negativity.
  • Universities are pillars of scientific research on the COVID-19 frontlines, they bring facts in times of uncertainty and fake news, and, in a bad economy, education is a personal floatation device.
Keep reading Show less

An ancient device too advanced to be real gives up its secrets at last

Researchers present what they’ve learned now that they can read the tiny text inside the Antikythera mechanism.

Exploded view of Antikythera mechanism (Peulle/Wikimedia)
Surprising Science

Though it it seemed to be just a corroded lump of some sort when it was found in a shipwreck off the coast of Greece near Antikythera in 1900, in 1902 archaeologist Valerios Stais, looking at the gear embedded in it, guessed that what we now call the “Antikythera mechanism" was some kind of astronomy-based clock. He was in the minority—most agreed that something so sophisticated must have entered the wreck long after its other 2,000-year-old artifacts. Nothing like it was believed to have existed until 1,500 years later.

Keep reading Show less

Hyper-innovation: COVID-19 will forever change the way we teach kids

The institutional barriers that have often held creative teaching back are being knocked down by the coronavirus era.

Future of Learning
  • Long-held structures in the education system, like classroom confines and schedules, have held back innovation for a long time, says education leader Richard Culatta.
  • In the coronavirus era, we have been able to shake some of those rigid structures loose, making way for creativity and, ultimately, a more open mindset.
  • When creativity and technology combine, learning can become so much more than delivering content to a student. Culatta gives two stunning examples: one of a biotech class, and another involving a student discovering a star.
Keep reading Show less

Algorithms associating appearance and criminality have a dark past

We'd like to think that judging people's worth based on the shape of their head is a practice that's behind us.

PATRICK KOVARIK/AFP via Getty Images
Culture & Religion

'Phrenology' has an old-fashioned ring to it. It sounds like it belongs in a history book, filed somewhere between bloodletting and velocipedes.

Keep reading Show less
Scroll down to load more…