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Indigenous people have been on the far northeastern edge of Canada for most of the last 10,000 years, moving in shortly after the ice retreated from the Last Glacial Maximum. Archaeological evidence suggests that people with distinct cultural traditions inhabited the region at least three different times with a possible hiatus for a period between 2,000 and 3,000 years ago. Now, researchers who’ve examined genetic evidence from mitochondrial DNA provide evidence that two of those groups, known as the Maritime Archaic and Beothuk, brought different matrilines to the island, adding further support to the notion that those groups had distinct population histories. The findings are published in Current Biology on October 12. “Our paper suggests, based purely on mitochondrial DNA, that the Maritime Archaic were not the direct ancestors of the Beothuk and that the two groups did not share a very recent common ancestor,” says Ana Duggan of McMaster University. “This in turn implies that the island of Newfoundland was populated multiple times by distinct groups.” The relationship between the older Maritime Archaic population and Beothuk hadn’t been clear from the archaeological record. With permission from the current-day indigenous community, Duggan and her colleagues, led by Hendrik Poinar, examined the mitochondrial genome diversity of 74 ancient remains from the island together with the archaeological record and dietary isotope profiles. All samples were collected from tiny amounts of bone or teeth. The sample set included a Maritime Archaic subadult more than 7,700 years old found in the L’Anse Amour burial mound, the oldest known burial mound in North America and one of the first manifestations of the Maritime Archaic tradition. The majority of the Beothuk samples came from the Notre Dame Bay area, where the Beothuk retreated in response to European expansions. Most of those samples are from people that lived on the island within the last 300 years. The DNA evidence showed that the two groups didn’t share a common maternal ancestor in the recent past, but rather one that coalesces sometime in the more distant past. “These data clearly suggest that the Maritime Archaic people are not the direct maternal ancestors of the Beothuk and thus that the population history of the island involves multiple independent arrivals by indigenous peoples followed by habitation for many generations,” the researchers write. “This shows the extremely rich population dynamics of early peoples on the furthest northeastern edge of the continent.”

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Indigenous people have been on the far northeastern edge of Canada for most of the last 10,000 years, moving in shortly after the ice retreated from the Last Glacial Maximum. Archaeological evidence suggests that people with distinct cultural traditions inhabited the region at least three different times with a possible hiatus for a period between 2,000 and 3,000 years ago.

Now, researchers who’ve examined genetic evidence from mitochondrial DNA provide evidence that two of those groups, known as the Maritime Archaic and Beothuk, brought different matrilines to the island, adding further support to the notion that those groups had distinct population histories.

“Our paper suggests, based purely on mitochondrial DNA, that the Maritime Archaic were not the direct ancestors of the Beothuk and that the two groups did not share a very recent common ancestor,” says Ana Duggan of McMaster University. “This in turn implies that the island of Newfoundland was populated multiple times by distinct groups.”

The relationship between the older Maritime Archaic population and Beothuk hadn’t been clear from the archaeological record. With permission from the current-day indigenous community, Duggan and her colleagues, led by Hendrik Poinar, examined the mitochondrial genome diversity of 74 ancient remains from the island together with the archaeological record and dietary isotope profiles. All samples were collected from tiny amounts of bone or teeth.

The sample set included a Maritime Archaic subadult more than 7,700 years old found in the L’Anse Amour burial mound, the oldest known burial mound in North America and one of the first manifestations of the Maritime Archaic tradition. The majority of the Beothuk samples came from the Notre Dame Bay area, where the Beothuk retreated in response to European expansions. Most of those samples are from people that lived on the island within the last 300 years. The DNA evidence showed that the two groups didn’t share a common maternal ancestor in the recent past, but rather one that coalesces sometime in the more distant past.

“These data clearly suggest that the Maritime Archaic people are not the direct maternal ancestors of the Beothuk and thus that the population history of the island involves multiple independent arrivals by indigenous peoples followed by habitation for many generations,” the researchers write. “This shows the extremely rich population dynamics of early peoples on the furthest northeastern edge of the continent.”

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Brain waves reflect different types of learning

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Figuring out how to pedal a bike and memorizing the rules of chess require two different types of learning, and now for the first time, researchers have been able to distinguish each type of learning by the brain-wave patterns it produces.

When neurons fire, they produce electrical signals that combine to form brain waves that oscillate at different frequencies. “Our ultimate goal is to help people with learning and memory deficits,” notes Miller. “We might find a way to stimulate the human brain or optimize training techniques to mitigate those deficits.”

The neural signatures could help identify changes in learning strategies that occur in diseases such as Alzheimer’s, with an eye to diagnosing these diseases earlier or enhancing certain types of learning to help patients cope with the disorder, says Roman F. Loonis, a graduate student in the Miller Lab and first author of the paper. Picower Institute research scientist Scott L. Brincat and former MIT postdoc Evan G. Antzoulatos, now at the University of California at Davis, are co-authors.

Explicit versus implicit learning

Scientists used to think all learning was the same, Miller explains, until they learned about patients such as the famous Henry Molaison or “H.M.,” who developed severe amnesia in 1953 after having part of his brain removed in an operation to control his epileptic seizures. Molaison couldn’t remember eating breakfast a few minutes after the meal, but he was able to learn and retain motor skills that he learned, such as tracing objects like a five-pointed star in a mirror.

“H.M. and other amnesiacs got better at these skills over time, even though they had no memory of doing these things before,” Miller says.

The divide revealed that the brain engages in two types of learning and memory — explicit and implicit.

Explicit learning “is learning that you have conscious awareness of, when you think about what you’re learning and you can articulate what you’ve learned, like memorizing a long passage in a book or learning the steps of a complex game like chess,” Miller explains.

“Implicit learning is the opposite. You might call it motor skill learning or muscle memory, the kind of learning that you don’t have conscious access to, like learning to ride a bike or to juggle,” he adds. “By doing it you get better and better at it, but you can’t really articulate what you’re learning.”

Many tasks, like learning to play a new piece of music, require both kinds of learning, he notes.

Brain waves from earlier studies

When the MIT researchers studied the behavior of animals learning different tasks, they found signs that different tasks might require either explicit or implicit learning. In tasks that required comparing and matching two things, for instance, the animals appeared to use both correct and incorrect answers to improve their next matches, indicating an explicit form of learning. But in a task where the animals learned to move their gaze one direction or another in response to different visual patterns, they only improved their performance in response to correct answers, suggesting implicit learning.

What’s more, the researchers found, these different types of behavior are accompanied by different patterns of brain waves.

During explicit learning tasks, there was an increase in alpha2-beta brain waves (oscillating at 10-30 hertz) following a correct choice, and an increase delta-theta waves (3-7 hertz) after an incorrect choice. The alpha2-beta waves increased with learning during explicit tasks, then decreased as learning progressed. The researchers also saw signs of a neural spike in activity that occurs in response to behavioral errors, called event-related negativity, only in the tasks that were thought to require explicit learning.

The increase in alpha-2-beta brain waves during explicit learning “could reflect the building of a model of the task,” Miller explains. “And then after the animal learns the task, the alpha-beta rhythms then drop off, because the model is already built.”

By contrast, delta-theta rhythms only increased with correct answers during an implicit learning task, and they decreased during learning. Miller says this pattern could reflect neural “rewiring” that encodes the motor skill during learning.

“This showed us that there are different mechanisms at play during explicit versus implicit learning,” he notes.

Future Boost to Learning

Loonis says the brain wave signatures might be especially useful in shaping how we teach or train a person as they learn a specific task. “If we can detect the kind of learning that’s going on, then we may be able to enhance or provide better feedback for that individual,” he says. “For instance, if they are using implicit learning more, that means they’re more likely relying on positive feedback, and we could modify their learning to take advantage of that.”

The neural signatures could also help detect disorders such as Alzheimer’s disease at an earlier stage, Loonis says. “In Alzheimer’s, a kind of explicit fact learning disappears with dementia, and there can be a reversion to a different kind of implicit learning,” he explains. “Because the one learning system is down, you have to rely on another one.”

Earlier studies have shown that certain parts of the brain such as the hippocampus are more closely related to explicit learning, while areas such as the basal ganglia are more involved in implicit learning. But Miller says that the brain wave study indicates “a lot of overlap in these two systems. They share a lot of the same neural networks.”

New type of stem cell line produced offers expanded potential for research and treatments

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Researchers at the Wellcome Trust Sanger Institute and their collaborators have created Expanded Potential Stem Cells (EPSCs) in mice, for the first time, that have a greater potential for development than current stem cell lines. These stem cells have the features of the very first cells in the developing embryo, and can develop into any type of cell.

The researchers also believe that their study could have implications for human regenerative medicine and for understanding miscarriage and developmental disorders.

Stem cells have the ability to develop into other cell types, and existing stem cell lines are already extremely useful for research into development, disease and treatments. However, the two currently available types of stem cell lines — Embryonic Stem cells (ES) and induced Pluripotent Stem cells (iPS) — have certain limitations. It is not currently possible for them to form every type of cell since they are already excluded from developing certain cell lineages.

To discover new stem cells for use in research and regenerative medicine, the researchers created a way of culturing cells from the earliest stage of development, when the fertilised egg has only divided into 4 or 8 cells that are still considered to retain some totipotency — the ability to produce all cell types. Their hypothesis was that these cells should be less programmed than ES cells, which are taken from the around-100-cell stage of development — called a blastocyst. They grew these early cells in a special growth condition that inhibited key development signals and pathways.

The scientists discovered that their new cultured cells kept the desired development characteristics of the earliest cells and named them Expanded Potential Stem Cells (EPSCs). Importantly, they were also able to reprogramme mouse ES cells and iPS cells in the new condition and create EPSCs from these cells, turning back the development clock to the very earliest cell type.

Dr Pentao Liu, lead researcher of this project, from the Wellcome Trust Sanger Institute and an affiliate faculty member of the Wellcome Trust-MRC Stem Cell Institute, University of Cambridge, said: “The earliest cell is like a blank piece of paper, in theory it should have the greatest development potential. This is the first time that stable stem cell lines of these earliest mouse cells have been possible, and we see that they do indeed keep the molecular features of the 4-8 cell embryo and can develop into any cell type.”

As a fertilised egg develops into a blastocyst, it produces cells that will form the embryo — where ES cells come from — and two other types of cell that will develop into the placenta or the yolk sac. It is possible to establish three different types of stem cells — including ES cells — from these three cell types in the blastocyst. EPSCs are the first stem cells that are able to produce all three types of blastocyst stem cells, which gives them much greater potential for development.

Dr Jian Yang, a first author on the paper from the Wellcome Trust Sanger Institute, said: “EPSCs provide a platform to study early embryo cells in detail at the molecular level to understand development, not only in mouse, but ultimately in future in humans. This new method of producing stem cells could be enormously helpful for studying development, more efficiently generating functional human cells, and researching treatments for pregnancy problems such as pre-eclampsia and miscarriages.”

Professor Hiro Nakauchi, a co-author on the paper from Stanford University, said: “This is a fantastic achievement, by working with the very earliest cells, this study has created stem cell lines that can form both embryonic and all the extra-embryonic cells. The methods and insights from this study in mice could be used to help establish cultures of similar stem cells from other mammalian species, including those where no ES or iPS cell lines are available yet. The research also has great implications for human regenerative medicine as stem cells with improved development potential open up new opportunities. Further research in this area is vital, so that we can properly explore the potential of these cells.”

Baby talk in any language: Shifting the timbre of our voices

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When talking with their young infants, parents instinctively use “baby talk,” a unique form of speech including exaggerated pitch contours and short, repetitive phrases. Now, They shift the timbre of their voice in a rather specific way. The findings hold true regardless of a mother’s native language.

“We use timbre, the tone color or unique quality of a sound, all the time to distinguish people, animals, and instruments,” says Elise Piazza from Princeton University. “We found that mothers alter this basic quality of their voices when speaking to infants, and they do so in a highly consistent way across many diverse languages.”

Timbre is the reason it’s so easy to discern idiosyncratic voices — the famously velvety sound of Barry White, the nasal tone of Gilbert Gottfried, and the gravelly sound of Tom Waits — even if they’re all singing the same note, Piazza explains.

Piazza and her colleagues at the Princeton Baby Lab, including Marius Catalin Iordan and Casey Lew-Williams, are generally interested in the way children learn to detect structure in the voices around them during early language acquisition. In the new study, they decided to focus on the vocal cues that parents adjust during baby talk without even realizing they’re doing it.

The researchers recorded 12 English-speaking mothers while they played with and read to their 7- to 12-month-old infants. They also recorded those mothers while they spoke to another adult.

After quantifying each mother’s unique vocal fingerprint using a concise measure of timbre, the researchers found that a computer could reliably tell the difference between infant- and adult-directed speech. In fact, using an approach called machine learning, the researchers found that a computer could learn to differentiate baby talk from normal speech based on just one second of speech data. The researchers verified that those differences couldn’t be explained by pitch or background noise.

The next question was whether those differences would hold true in mothers speaking other languages. The researchers enlisted another group of 12 mothers who spoke nine different languages, including Spanish, Russian, Polish, Hungarian, German, French, Hebrew, Mandarin, and Cantonese. Remarkably, they found that the timbre shift observed in English-speaking mothers was highly consistent across those languages from around the world.

“The machine learning algorithm, when trained on English data alone, could immediately distinguish adult-directed from infant-directed speech in a test set of non-English recordings and vice versa when trained on non-English data, showing strong generalizability of this effect across languages,” Piazza says. “Thus, shifts in timbre between adult-directed and infant-directed speech may represent a universal form of communication that mothers implicitly use to engage their babies and support their language learning.”

The researchers say the next step is to explore how the timbre shift helps infants in learning. They suspect that the unique timbre fingerprint could help babies learn to differentiate and direct their attention to their mother’s voice from the time they are born.

And don’t worry, dads. While the study was done in mothers to keep the pitches more consistent across study participants, the researchers say it’s likely the results will apply to fathers, too.

Paleogenomic analysis sheds light on Easter Island mysteries

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Easter Island is a place of mystery that has captured the public imagination. Famous for ancient carved statues and a location so remote it boggles the mind, the island presents a captivating puzzle for researchers eager to understand how and when it became inhabited, and by whom.

New paleogenomic research conducted by an international team led by UC Santa Cruz sheds light on those questions by ruling out the likelihood that inhabitants of Easter Island intermixed with South Americans prior to the arrival of Europeans on the island in 1722.

The team analyzed bone fragments from the ancient skeletal remains of five individuals that were excavated in the 1980s and became part of the Kon-Tiki Museum’s collection in Oslo. Each sample, which had been used in a previous study, yielded less than 200 milligrams of material. Three individuals lived prior to European contact, and two lived after.

“We found no evidence of gene flow between the inhabitants of Easter Island and South America,” said Fehren-Schmitz. “We were really surprised we didn’t find anything. There’s a lot of evidence that seems plausible, so we were convinced we would find direct evidence of pre-European contact with South America, but it wasn’t there.”

Questions surrounding Pacific islanders’ contact with South Americans are hotly debated among anthropologists. An earlier study found genetic traces of early inhabitants of the Americas in present-day indigenous residents of Easter Island. Those researchers posited that the intermixing most likely occurred between 1280 and 1425. Fehren-Schmitz was the first to use paleogenomic analysis to directly test that hypothesis; his findings indicate that contact must have taken place after 1722.

Slavery, whaling, mass deportations, and other activities that followed European contact gave rise to opportunities for intermixing that likely left the genetic imprint seen in islanders today, he said.

“The most likely scenario is that there wasn’t a single episode,” said Fehren-Schmitz. Acknowledging that his results answer one question but leave many others unanswered, he said, “The story is simply more complicated than we expected.”

A member of the UC Santa Cruz Paleogenomics Laboratory, Fehren-Schmitz uses DNA sequences recovered from preserved biological remains to trace molecular evolutionary processes through time. The analysis of DNA from ancient humans sheds light on human evolution, researchers’ understanding of how humans diverged and interacted over time, and how the forces of culture and biology have shaped human genetic diversity.

“This study highlights the value of ancient DNA to test hypotheses about past population dynamics,” said Fehren-Schmitz. “We know the island’s modern populations have some Native American ancestry, and now we know that early inhabitants did not. So the big questions remain: Where and when did these groups interact to change the genetic signature of Easter Islanders?”

One of the mysteries of Easter Island — also called Rapa Nui — is how the island came to be populated. Located nearly 1,300 miles from the nearest inhabited island, it is 2,200 miles from central Chile on the nearest continent of South America. Some archaeologists have suggested that sea travel between Polynesia and the Americas was plausible, leading to the intermingling of those populations and perhaps even the peopling of the Americas. But plausibility isn’t proof, noted Fehren-Schmitz.

“We want to do more work to determine more precisely when this gene flow between Native Americans and the people of Rapa Nui occurred, and where in the Americas it originated,” he said. “The population dynamics of these regions are fascinating. We need to study the ancient populations of other islands — if remains exist.”

This project also demonstrates the value of using recently developed research methods on materials from older museum collections. Tropical conditions make preservation difficult, and rib fragments are generally too soft to be desirable, but recent technological advances opened up new possibilities, said Fehren-Schmitz.

“Our methodologies have evolved so much in the last five years that we might need to re-study samples we gave up on in the past to see if we can get DNA out of them,” he added.

 

‘Turbo charge’ for your brain?

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Two brain regions — the medial frontal and lateral prefrontal cortices — control most executive function. Researchers used high-definition transcranial alternating current stimulation (HD-tACS) to synchronize oscillations between them, improving brain processing. De-synchronizing did the opposite.

Robert Reinhart calls the medial frontal cortex the “alarm bell of the brain.”

“If you make an error, this brain area fires,” says Reinhart, an assistant professor of psychological and brain sciences at Boston University. “If I tell you that you make an error, it also fires. If something surprises you, it fires.” Hit a sour note on the piano and the medial frontal cortex lights up, helping you correct your mistake as fast as possible. In healthy people, this region of the brain works hand in hand (or perhaps lobe in lobe) with a nearby region, the lateral prefrontal cortex, an area that stores rules and goals and also plays an important role in changing our decisions and actions.

“These are maybe the two most fundamental brain areas involved with executive function and self-control,” says Reinhart, who used a new technique called high-definition transcranial alternating current stimulation (HD-tACS) to stimulate these two regions with electrodes placed on a participant’s scalp. Using this new technology, he found that improving the synchronization of brain waves, or oscillations, between these two regions enhanced their communication with each other, allowing participants to perform better on laboratory tasks related to learning and self-control. Conversely, de-synchronizing or disrupting the timing of the brain waves in these regions impaired participants’ ability to learn and control their behavior, an effect that Reinhart could quickly fix by changing how he delivered the electrical stimulation.  suggests that electrical stimulation can quickly — and reversibly — increase or decrease executive function in healthy people and change their behavior. These findings may someday lead to tools that can enhance normal brain function, possibly helping treat disorders from anxiety to autism.

“We’re always looking for a link between brain activity and behavior — it’s not enough to have just one of those things. That’s part of what makes this finding so exciting,” says David Somers, a BU professor of psychological and brain sciences, who was not involved with the study. Somers likens the stimulation to a “turbo charge” for your brain. “It’s really easy to mess things up in the brain but much harder to actually improve function.”

Research has recently suggested that populations of millions of cells in the medial frontal cortex and the lateral prefrontal cortex may communicate with each other through the precise timing of their synchronized oscillations, and these brain rhythms appear to occur at a relatively low frequency (about four to eight cycles per second). While scientists have studied these waves before, Reinhart is the first to use HD-tACS to test how these populations of cells interact and whether their interactions are behaviorally useful for learning and decision-making. In his work, funded by the National Institutes of Health, Reinhart is able to use HD-tACS to isolate and alter these two specific brain regions, while also recording participants’ electrical brain activity via electroencephalogram (EEG).

“The science is much stronger, much more precise than what’s been done earlier,” says Somers.

In his first round of studies, Reinhart tested 30 healthy participants. Each subject wore a soft cap fitted with electrodes that stimulated brain activity, while additional electrodes monitored brain waves. (The procedure is safe, noninvasive, and doesn’t hurt, says Reinhart. “There’s a slight tingling for the first 30 seconds,” he says, “and then people habituate to it.”) Then, for 40 minutes, participants performed a time-estimation learning task, pressing a button when they thought 1.7 seconds had passed. Each time, the computer gave them feedback: too fast, too slow, or just right.

Reinhart tested each of the 30 participants three times, once up-regulating the oscillations, once disrupting them, and once doing nothing. In tests where Reinhart cranked up the synchrony between the two brain regions, people learned faster, made fewer errors, and — when they did make an error — adjusted their performance more accurately. And, when he instead disrupted the oscillations and decreased the synchrony — in a very rough sense, flicking the switch from “smart” to “dumb” — subjects made more errors and learned slower. The effects were so subtle that the people themselves did not notice any improvement or impairment in the task, but the results were statistically significant.

Reinhart then replicated the experiment in 30 new participants, adding another study parameter by looking at only one side of the brain at a time. In all cases, he found that the right hemisphere of the brain was more relevant to changing behavior.

Then came the most intriguing part of the study. Thirty more participants came in and tried the task. First, Reinhart temporarily disrupted each subject’s brain activity, watching as their brain waves de-synchronized and their performance on the task declined. But this time, in the middle of the task, Reinhart switched the timing of the stimulation — again, turning the knob from “dumb” to “smart.” Participants recovered their original levels of brain synchrony and learning behavior within minutes.

“We were shocked by the results and how quickly the effects of the stimulation could be reversed,” says Reinhart.

Though Reinhart cautions that these results are very preliminary, he notes that many psychiatric and neurological disorders — including anxiety, Parkinson’s, autism, schizophrenia, ADHD, and Alzheimer’s — demonstrate disrupted oscillations. Currently, most of these disorders are treated with drugs that act on receptors throughout the brain. “Drugs are really messy,” says Reinhart. “They often affect very large regions of brain.” He imagines, instead, a future with precisely targeted brain stimulation that acts only on one critical node of a brain network, “like a finer scalpel.” Reinhart’s next line of research will test the technology on people with anxiety disorders.

There is also, of course, the promise of what the technology might offer to healthy brains. Several companies already market brain stimulation devices that claim to both enhance learning and decrease anxiety. YouTube videos show how to make your own, with double-A batteries and off-the-shelf electronics, a practice Reinhart discourages. “You can hurt yourself,” he says. “You can get burned and have current ringing around your head for days.”

He does, however, see the appeal. “I had volunteers in previous research who came back and said, ‘Hey, where can I get one of these? I’d love to have it prior to an exam,'” he says. “That was after we debriefed them and they were reading the papers about it.”

Somers notes that there are still many questions to answer about the technology before it goes mainstream: How long can the effect last? How big can you make it? Can you generalize from a simple laboratory task to much more complicated endeavors? “But the biggest question,” says Somers, “is how far you can go with this technology.”

“Think about any given workday,” says Somers. “You need to be really ‘on’ for one meeting, so you set aside some time on your lunch break for some brain stimulation. I think a lot of people would be really into that — it would be like three cups of coffee without the jitters.”

Exotic quantum particle observed in bilayer graphene

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Wang Fong-Jen Professor of Mechanical Engineering at Columbia Engineering, has definitively observed an intensely studied anomaly in condensed matter physics the even-denominator fractional quantum Hall (FQH) state — via transport measurement in bilayer graphene.

“Observing the 5/2 state in any system is a remarkable scientific opportunity, since it encompasses some of the most perplexing concepts in modern condensed matter physics, such as emergence, quasi-particle formation, quantization, and even superconductivity,” Dean says. “Our observation that, in bilayer graphene, the 5/2 state survives to much higher temperatures than previously thought possible not only allows us to study this phenomenon in new ways, but also shifts our view of the FQH state from being largely a scientific curiosity to now having great potential for real-world applications, particularly in quantum computing.”

First discovered in the 1980s in gallium arsenide (GaAs) heterostructures, the 5/2 fractional quantum hall state remains the singular exception to the otherwise strict rule that says fractional quantum hall states can only exist with odd denominators. Soon after the discovery, theoretical work suggested that this state could represent an exotic type of superconductor, notable in part for the possibility that such a phase could enable a fundamentally new approach to quantum computation. However, confirmation of these theories has remained elusive, largely due to the fragile nature of the state; in GaAs it is observable only in the highest quality samples and even then appearing only at milikelvin temperaures (as much as 10,000 times colder than the freezing point of water).

The Columbia team has now observed this same state in bilayer graphene and appearing at much higher temperatures??reaching several Kelvin. “While it’s still 100 times colder than the freezing point of water, seeing the even-denominator state at these temperatures opens the door to a whole new suite of experimental tools that previously were unthinkable,” says Dean. “After several decades of effort by researchers all over the world, we may finally be close to solving the mystery of the 5/2.”

One of the outstanding problems in the field of modern condensed matter physics is understanding the phenomenon of “emergence,” the result of a large collection of quantum particles behaving in concert due to interactions between the particles and giving rise to new characteristics that are not a feature of the individual parts. For instance, in superconductors, a large number of electrons all collapse to a single quantum state, which can then propagate through a metal without any energy loss. The fractional quantum Hall effect is another state in which electrons collude with one another, in the presence of a magnetic field, resulting in quasiparticles with potentially exotic quantum properties.

Very difficult to predict theoretically, emergence often challenges our foundational understanding of how particles behave. For example, since any two electrons have the same charge, we think of electrons as objects that want to repel each other. However, in a superconducting metal, electrons unexpectedly pair up, forming a new object known as a cooper pair. Individual electrons scatter when moving through a metal, giving rise to resistance, but spontaneously formed cooper pairs behave collectively in such a way that they move through the material with no resistance at all.

“Think of trying to make your way through a crowd at a rock concert where everyone is dancing with a lot of energy and constantly bumping into you, compared to a ballroom dance floor where pairs of dancers are all moving in the same, carefully choreographed way, and it is easy to avoid each other,” says Dean. “One of the reasons that makes the even-denominator fractional quantum Hall effect so fascinating is that its origin is believed to be very similar to that of a superconductor, but, instead of simply forming cooper pairs, an entirely new kind of quantum particle emerges.”

According to quantum mechanics, elementary particles fall into two categories, Fermions and Bosons, and behave in very different ways. Two Fermions, such as electrons, cannot occupy the same state, which is why, for example, the electrons in atoms fill successive orbitals. Bosons, such as photons, or particles of light, can occupy the same state, allowing them to act coherently as in the light emission from a laser. When two identical particles are interchanged, the quantum mechanical wave-function describing their combined state is multiplied by a phase factor of 1 for Bosons, and -1 for Fermions.

Soon after the discovery of the fractional quantum hall effect, it was suggested on theoretical grounds that the quasiparticles associated with this state behave neither as Bosons nor Fermions but instead what is called an anyon: when anyon quasiparticles are interchanged, the phase factor is neither 1 nor -1 but is fractional. Despite several decades of effort, there still is no conclusive experimental proof confirming that these quasiparticles are anyons. The 5/2 state?a non-abelian anyon?is thought to be even more exotic. In theory, non-abelian anyons obey anyonic statistics as in other fractional quantum Hall states, but with the special feature that this phase cannot simply be undone by reversing the process. This inability to simply unwind the phase would make any information stored in the system uniquely stable, and is why many people believe the 5/2 could be a great candidate for quantum computation.

“Demonstration of the predicted 5/2 statistics would represent a tremendous achievement,” says Dean. “In many regards, this would confirm that, by fabricating a material system with just the right thickness and just the right number of electrons, and then applying just the right magnetic fields, we could effectively engineer fundamentally new classes of particles, with properties that do not otherwise exist among known particles naturally found in the universe. We still have no conclusive evidence that the 5/2 state exhibits non-abelian properties, but our discovery of this state in bilayer graphene opens up exciting new opportunities to test these theories.”

Until now, all of those conditions have needed to be not only just right but also extreme. In conventional semi-conductors, the even-denominator states are very difficult to isolate, and exist only for ultra-pure materials, at extremely low temperatures and high magnetic fields. While certain features of the state have been observable devising experiments that could investigate the state without destroying it, has been challenging.

“We needed a new platform,” says Hone. “With the successful isolation of graphene, these atomically thin layers of carbon atoms emerged as a promising platform for the study of electrons in 2D in general. One of the keys is that electrons in graphene interact even more strongly than in conventional 2D electron systems, theoretically making effects such as the even-denominator state even more robust. But while there have been predictions that bilayer graphene could host the long-sought even-denominator states, at higher temperatures than seen before, these predictions have not been realized due mostly the difficulty of making graphene clean enough.”

The Columbia team built on many years of pioneering work to improve the quality of graphene devices, creating ultra-clean devices entirely from atomically flat 2D materials: bilayer graphene for the conducting channel, hexagonal boron nitride as a protective insulator, and graphite used for electrical connections and as a conductive gate to change the charge carrier density in the channel.

A crucial component of the research was having access to the high magnetic fields tools available at the National High Magnetic Field Laboratory in Tallahassee, Fla., a nationally funded user facility with which Hone and Dean have had extensive collaborations. They studied the electrical conduction through their devices under magnetic fields up to 34 Tesla, and achieved clear observation of the even-denominator states.

“By tilting the sample with respect to the magnetic field, we were able to provide new confirmation that this FQH state has many of the properties predicted by theory, such as being spin-polarized,” says Jia Li, the paper’s lead author and post-doctoral researcher working with Dean and Hone. “We also discovered that in bilayer graphene, this state can be manipulated in ways that are not possible in conventional materials.”

The Columbia team’s result, which demonstrates measurement in transport — how electrons flow in the system — is a crucial step forward towards confirming the possible exotic origin of the even denominator state. Their findings are reported contemporaneously with a similar report by a research group at University of California, Santa Barbara. The UCSB study observed the even denominator state by capacitance measurement, which probes the existence of an electrical gap associated with the onset of the state.

“For many decades now it has been thought that if the 5/2 state does indeed represent a non-abelian anyon, it could theoretically revolutionize efforts to build a quantum computer,” Dean observes. “In the past, however, the extreme conditions necessary to see the state at all, let alone use it for computation, were always a major concern of practicality. Our results in bilayer graphene suggest that this dream may now not actually be so far from reality.”