��Ī - National University of Singapore

Diamonds and rust help unveil ‘impossible’ quasi-particles

sc604 — Tue, 05 Dec 2023 10:02:43 +0000

Researchers led by the ��Ī used a technique known as diamond quantum sensing to observe swirling textures and faint magnetic signals on the surface of hematite, a type of iron oxide.

The researchers observed that magnetic monopoles in hematite emerge through the collective behaviour of many spins (the angular momentum of a particle). These monopoles glide across the swirling textures on the surface of the hematite, like tiny hockey pucks of magnetic charge. This is the first time that naturally occurring emergent monopoles have been observed experimentally.

The research has also shown the direct connection between the previously hidden swirling textures and the magnetic charges of materials like hematite, as if there is a secret code linking them together. The results, which could be useful in enabling next-generation logic and memory applications, are reported in the journal Nature Materials.

According to the equations of James Clerk Maxwell, a giant of ��Ī physics, magnetic objects, whether a fridge magnet or the Earth itself, must always exist as a pair of magnetic poles that cannot be isolated.

“The magnets we use every day have two poles: north and south,” said Professor Mete Atatüre, who led the research. “In the 19th century, it was hypothesised that monopoles could exist. But in one of his foundational equations for the study of electromagnetism, James Clerk Maxwell disagreed.”

Atatüre is Head of ��Ī’s Cavendish Laboratory, a position once held by Maxwell himself. “If monopoles did exist, and we were able to isolate them, it would be like finding a missing puzzle piece that was assumed to be lost,” he said.

About 15 years ago, scientists suggested how monopoles could exist in a magnetic material. This theoretical result relied on the extreme separation of north and south poles so that locally each pole appeared isolated in an exotic material called spin ice.

However, there is an alternative strategy to find monopoles, involving the concept of emergence. The idea of emergence is the combination of many physical entities can give rise to properties that are either more than or different to the sum of their parts.

Working with colleagues from the University of Oxford and the National University of Singapore, the ��Ī researchers used emergence to uncover monopoles spread over two-dimensional space, gliding across the swirling textures on the surface of a magnetic material.

The swirling topological textures are found in two main types of materials: ferromagnets and antiferromagnets. Of the two, antiferromagnets are more stable than ferromagnets, but they are more difficult to study, as they don’t have a strong magnetic signature.

To study the behaviour of antiferromagnets, Atatüre and his colleagues use an imaging technique known as diamond quantum magnetometry. This technique uses a single spin – the inherent angular momentum of an electron – in a diamond needle to precisely measure the magnetic field on the surface of a material, without affecting its behaviour.

For the current study, the researchers used the technique to look at hematite, an antiferromagnetic iron oxide material. To their surprise, they found hidden patterns of magnetic charges within hematite, including monopoles, dipoles and quadrupoles.

“Monopoles had been predicted theoretically, but this is the first time we’ve actually seen a two-dimensional monopole in a naturally occurring magnet,” said co-author Professor Paolo Radaelli, from the University of Oxford.

“These monopoles are a collective state of many spins that twirl around a singularity rather than a single fixed particle, so they emerge through many-body interactions. The result is a tiny, localised stable particle with diverging magnetic field coming out of it,” said co-first author Dr Hariom Jani, from the University of Oxford.

“We’ve shown how diamond quantum magnetometry could be used to unravel the mysterious behaviour of magnetism in two-dimensional quantum materials, which could open up new fields of study in this area,” said co-first author Dr Anthony Tan, from the Cavendish Laboratory. “The challenge has always been direct imaging of these textures in antiferromagnets due to their weaker magnetic pull, but now we’re able to do so, with a nice combination of diamonds and rust.”

The study not only highlights the potential of diamond quantum magnetometry but also underscores its capacity to uncover and investigate hidden magnetic phenomena in quantum materials. If controlled, these swirling textures dressed in magnetic charges could power super-fast and energy-efficient computer memory logic.

The research was supported in part by the Royal Society, the Sir Henry Royce Institute, the European Union, and the Engineering and Physical Sciences Research Council (EPSRC), part of UK Research and Innovation (UKRI).

Reference:
K C Tan, Hariom Jani, Michael Högen et al. ‘Revealing Emergent Magnetic Charge in an Antiferromagnet with Diamond Quantum Magnetometry.’ Nature Materials (2023). DOI: 10.1038/s41563-023-01737-4.

For more information on energy-related research in ��Ī, please visit the Energy IRC, which brings together ��Ī’s research knowledge and expertise, in collaboration with global partners, to create solutions for a sustainable and resilient energy landscape for generations to come.

Researchers have discovered magnetic monopoles – isolated magnetic charges – in a material closely related to rust, a result that could be used to power greener and faster computing technologies.

If monopoles did exist, and we were able to isolate them, it would be like finding a missing puzzle piece that was assumed to be lost

Mete Atatüre

Anthony Tan and Michael Hoegen

Magnetic monopoles in hematite

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Taking ��Ī global

skbf2 — Fri, 01 Dec 2023 11:54:25 +0000

In 2013, ��Ī opened its first-ever overseas research centre, the ��Ī Centre for Advanced Research and Education in Singapore (CARES). Over the past decade, CARES has grown into a thriving community of 150 staff and researchers, working with partners to achieve scientific breakthroughs with a global impact.

Sleight-of-hand magic trick only fools monkeys with opposable thumbs

fpjl2 — Mon, 03 Apr 2023 14:27:26 +0000

By performing a famous magic trick for three species of monkey with differing hand structures, scientists have discovered that – in order to deceive – a conjuror needs the same anatomy as their audience.

Psychologists used a sleight-of-hand trick called the French drop, in which an object appears to vanish when a spectator assumes it is taken from one hand by the hidden thumb of the other hand.

The study, carried out by the ��Ī’s Comparative Cognition Lab, found that monkeys lacking opposable thumbs did not fall for the assumption – staying wise to the whereabouts of tasty treats a magician tried to make disappear.

The research suggest that sharing a biomechanical ability may be necessary for accurately anticipating the movements of those same limbs in other individuals.

This is true even when those apparently accurate predictions end in befuddlement at the hands of an illusionist. The study is published today in the journal Current Biology.

“Magicians use intricate techniques to mislead the observer into experiencing the impossible. It is a great way to study blind spots in attention and perception,” said Dr Elias Garcia-Pelegrin, who has practiced magic for a decade, and conducted the experimental work during his PhD at ��Ī.

“By investigating how species of primates experience magic, we can understand more about the evolutionary roots of cognitive shortcomings that leave us exposed to the cunning of magicians.”

“In this case, whether having the manual capability to produce an action, such as holding an item between finger and thumb, is necessary for predicting the effects of that action in others,” said Garcia-Pelegrin, recently appointed an assistant professor at the National University of Singapore.

The French drop is often the first trick any budding magician sets out to master.

A coin is displayed in one hand. The other hand reaches over and grabs it. The palm of the second hand faces inwards, with the magician’s thumb concealed behind fingers.

The audience knows the thumb is lurking – ready to grip – so assumes the coin has been taken when it is no longer visible. Their attention follows the second hand, only to find it empty at 'the reveal'. The magician had secretly dropped the coin into the palm of the original hand.

Food morsels replaced coins for the monkeys, and were given as rewards – but only if the animals guessed the correct hand. Scientists predicted that monkeys with opposable thumbs would act like human audiences: assume the hidden thumb had grabbed the item, and choose the wrong hand.

They repeatedly performed the French drop on 24 monkeys. Eight capuchins were dazzled with peanuts, eight squirrel monkeys with dried mealworms, and eight marmosets with marshmallows.

Capuchins are famed for dexterity, and use stone tools to crack nuts in the wild. They can waggle each finger, and have opposable thumbs allowing 'precision grip' between thumb and forefingers.

The capuchins were regularly fooled by the French drop (81% of the time). They mostly chose the empty second hand, and experienced a paucity of peanuts as a result.

Squirrel monkeys are much less dextrous than capuchins, with limited thumb rotation, but can oppose their thumbs. As such, they are still familiar with a hidden thumb interacting with fingers. However, they cannot perform a ‘precision grip’ in the same way as capuchins and humans.

Yet squirrel monkeys were routinely misled by vanishing mealworms (93% of the time). “Squirrel monkeys cannot do full precision grips, but they were still fooled. This suggests that a monkey doesn’t have to be expert in a movement in order to predict it, just roughly able to do it,” said Garcia-Pelegrin.

Marmosets do not have opposable thumbs. Their thumbs align with their fingers to make five equidistant digits, ideal for climbing thick tree trunks. Marmosets were rarely taken in by magic (just 6% of the time). They simply chose the hand in which the marshmallow was initially placed, and stuck with it.

Previous work from the ��Ī team shows that species without hands at all, in this case birds from the corvid family, namely Eurasian jays, make similar choices as marmosets when confronted with the French drop.

The team also tried nullifying the tricks by actually completing the hand-to-hand transfers, instead of misdirecting with a French drop. This time, the capuchins and squirrel monkeys anticipated correctly and dined out, and the marmosets missed out.

Finally, the scientists devised their own version of the French drop, which they call the “Power drop”. It utilises a hand action that all the monkey species can perform – essentially a full fist grab. The power drop fooled all of the monkey species the vast majority of the time.

“There is increasing evidence that the same parts of the nervous system used when we perform an action are also activated when we watch that action performed by others,” said Prof Nicola Clayton FRS, senior author of the study from ��Ī’s Department of Psychology.

“This mirroring in our neural motor system might explain why the French drop worked for the capuchins and squirrel monkeys but not for marmosets.”

“It’s about the embodiment of knowledge,” added Clayton. “How one’s fingers and thumbs move helps to shape the way we think, and the assumptions we make about the world – as well as what others might see, remember and anticipate, based on their expectations.”

“Our work raises the intriguing possibility that an individual’s inherent physical capability heavily influences their perception, their memory of what they think they saw, and their ability to predict manual movements of those around them.”

Another co-author of the study, Clive Wilkins, Artist in Residence at ��Ī’s Department of Psychology, is a professional magician and Member of the Magic Circle.

Illusion involving a hidden thumb confounds capuchin and squirrel monkeys for the same reason as humans – it misdirects the expected outcomes of actions they can carry out.

This mirroring in our neural motor system might explain why the French drop worked for the capuchins and squirrel monkeys but not for marmosets

Nicola Clayton

Not all monkeys are fooled by magic.

Elias Garcia-Pelegrin

A Humboldt's squirrel monkey is fooled by a French drop as part of the experiment.

Yes

Global Alliance approves five joint research projects

ag236 — Mon, 13 Nov 2017 13:07:33 +0000

The Global Alliance was formed in 2016 as a tripartite agreement between University of California, Berkeley, the ��Ī, and National University of Singapore in order to develop innovative research across the three universities to address research questions that could not be answered by one institution alone. There are three themes within the Global Alliance: Precision Medicine, Cities, and Smart Systems.

Following a second funding call in May 2017, the Management Selection Committee has approved funding of the following five collaborative research projects:

"Opportunities for ecological adaptation to flood hazards in major global cities: London, Singapore and San Francisco" (Principal Investigator: Professor Thomas Spencer)
"Machine learning tools for personalised diagnosis in dementia" (Principal Investigator: Professor Zoe Kourtzi)
"Healthy living in cities: my Personal Exposure Quality (MyPEQ)" (Principal investigator: Professor Rajasekhar Balasubramanian)
"Automating Approaches for Clinical Genome Interpretation" (Principal Investigator: Professor Steven Brenner)
"Skin Deformation Assay Platforms for Pathogen- and Patient-Specific Diagnostics and Drug Development" (Principal Investigator: Dr Katherine Brown)

The three universities are delighted to approve these collaborative projects which will build upon the combined strengths of the universities, as well as their distinctive regional insights, to develop unique solutions to global problems.

Professor Paul Alivisatos, Executive Vice Chancellor and Provost, University of California, Berkeley

Professor Chris Abell, Pro-Vice-Chancellor for Research, ��Ī

Professor Ho Teck Hua, Senior Deputy President and Provost Designate, National University of Singapore

UC Berkeley, the ��Ī and the National University of Singapore to support collaborative projects in themes including Precision Medicine, Cities and Smart Systems.

The text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes

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