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Patience is a virtue— sometimes discovery is just the first step

Quick notes

  • A Harvard professor discovered unknown properties of electrical currents in 1879

  • That discovery left half the story untold

  • One hundred and forty years later, an IBM researcher discovered how to read the rest of the story

  • It will transform scientists’ understanding of semiconductors

1879, Harvard University physicist Ewin Hall made a discovery that is still revealing its secrets.

Hall discovered that electrical currents bend when placed in a magnetic field. When they do, they produce a voltage and a new electrical field. That new electrical field is perpendicular to the current. Let’s call it “The Hall Effect” for short. To the surprise of no one, has a much longer and more detailed explanation of The Hall Effect.

Scientists have taken advantage of the effect to study the properties of some materials. Perhaps most significantly, they are used to study the properties of semiconductors that make up microchips.

Seeing half of the picture

The Hall Effect has been useful in relation to semiconductors and microchips, but in a limited way. One hundred and forty years after Edwin Hall made his first discovery, though, that’s all changed. Much fuller knowledge of The Hall Effect has finally emerged.

But before that’ll make any sense, let’s look at how it was being used before. Spoiler alert: lots of physics language coming!

Long Zheng/Flickr

As I’m sure you know and remember, and as reminds us:

[E]lectrical charges move through semi-conductors as discrete units called charge carriers: negatively charged electrons and positively charged “holes,” electron voids in the material that can move the same way that electrons can. Scientists use the Hall effect to figure out the properties of the charge carriers in a material, like how fast they move and how densely packed they are. More recently, they used the Hall effect to understand the effect of light on the materials they were studying….

Here’s the limitation:  techniques based on The Hall Effect can only measure the properties of the more numerous charge carrier (the majority charge carrier) and not the properties of both the minority and majority carriers at the same time. If there are more electrons, measurements will tell you only about the electrons. If there are more holes, measurements will tell you only about the holes. One doesn’t get the whole (pun intended) picture.

Revealing the other half of the picture

IBM researcher Oki Gunawan devised a method of extracting: “minority charge carrier information at the same time as the majority charge carrier information.” Gunawan’s method was reported in a paper in Nature called “Carrier-resolved photo-Hall effect.” Gunawan’s innovation:

enables us to simultaneously obtain the mobility and concentration of both majority and minority carriers, as well as the recombination lifetime, diffusion length and recombination coefficient.

So what?

Not to be rude, but this innovation has given scientists access to information that has been hidden for at least 140 years. But, why does Gunawan’s development of Edwin Hall’s 1879 discovery matter? It all comes down to semi-conductors. Semiconductors are important chip materials for use in all our favorite gadgets: tablets, smartphones, and computers. says they’re going to remain “the key elements for the majority of electronic systems, serving communications, signal processing, computing, and control applications in both the consumer and industrial markets.” So what’s good for semi-conductors is good for us. And Gunawan’s revelation of physics mysteries within The Hall Effect is good for semi-conductors.

Just ask

This new discovery and technology will help push semiconductor advances in both existing and emerging technologies. …[T]his could accelerate development of next-generation semiconductor technology such as better solar cells, better optoelectronics devices and new materials and devices for artificial intelligence technology.

Edwin Hall could never have imagined what might be left lurking in his 1879 discovery. He certainly could not have imagined the implications of his work – known and only imagined – 140 years later. Imagine what other layers of mystery remain to be revealed in quantum physics.

A deeper dive – Related reading from the 101:

– ‘Quantum consciousness’ will blow your mind | Science 101

The mysteries of quantum physics are profound and startling, but consciousness? 

– Time travel? Well, sort of | Science 101

At the tiniest quantum level of things, has one of the biggest concepts ever – time travel – been shown to be possible?