̽��ֱ�� of Cambridge - Mark Blamire

Some superconductors can also carry currents of ‘spin’

sc604 — Mon, 16 Apr 2018 15:00:00 +0000

Spin is a particle’s intrinsic angular momentum, and is normally carried in non-superconducting, non-magnetic materials by individual electrons. Spin can be ‘up’ or ‘down’, and for any given material, there is a maximum length that spin can be carried. In a conventional superconductor electrons with opposite spins are paired together so that a flow of electrons carries zero spin.

A few years ago, researchers from the ̽��ֱ�� of Cambridge showed that it was possible to create electron pairs in which the spins are aligned: up-up or down-down. ̽��ֱ��spin current can be carried by up-up and down-down pairs moving in opposite directions with a net charge current of zero. ̽��ֱ��ability to create such a pure spin supercurrent is an important step towards the team’s vision of creating a superconducting computing technology which could use massively less energy than the present silicon-based electronics.

Now, the same researchers have found a set of materials which encourage the pairing of spin-aligned electrons, so that a spin current flows more effectively in the superconducting state than in the non-superconducting (normal) state. Their results are reported in the journal Nature Materials.

“Although some aspects of normal state spin electronics, or spintronics, are more efficient than standard semiconductor electronics, their large-scale application has been prevented because the large charge currents required to generate spin currents waste too much energy,” said Professor Mark Blamire of Cambridge’s Department of Materials Science and Metallurgy, who led the research. “A fully-superconducting method of generating and controlling spin currents offers a way to improve on this.”

In the current work, Blamire and his collaborators used a multi-layered stack of metal films in which each layer was only a few nanometres thick. They observed that when a microwave field was applied to the films, it caused the central magnetic layer to emit a spin current into the superconductor next to it.

“If we used only a superconductor, the spin current is blocked once the system is cooled below the temperature when it becomes a superconductor,” said Blamire. “ ̽��ֱ��surprising result was that when we added a platinum layer to the superconductor, the spin current in the superconducting state was greater than in the normal state.”

Although the researchers have shown that certain superconductors can carry spin currents, so far these only occur over short distances. ̽��ֱ��next step for the research team is to understand how to increase the distance and how to control the spin currents.

̽��ֱ��research was funded by the Engineering and Physical Sciences Research Council (EPSRC).

Reference:
Kun-Rok Jeon et al. ‘Enhanced spin pumping into superconductors provides evidence for superconducting pure spin currents.’ Nature Materials (2018). DOI: 10.1038/s41563-018-0058-9

Researchers have shown that certain superconductors – materials that carry electrical current with zero resistance at very low temperatures – can also carry currents of ‘spin’. ̽��ֱ��successful combination of superconductivity and spin could lead to a revolution in high-performance computing, by dramatically reducing energy consumption.

Jason Robinson

Conceptual image of spin current flow in a superconductor

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

Yes

̽��ֱ��Electron Manifesto: transforming high performance computing with 'spintronics'

tdk25 — Wed, 26 Jul 2017 11:54:19 +0000

In the early days of the computer, calculators were room-sized and public demand was low. Now, it’s the reverse. Digital technology has become smaller and faster, and our dependence on it has grown.

We are almost desensitised to a stream of facts about the startling rate at which this is occurring. In 2016, IBM found that humans now create 2.5 quintillion bytes of data daily. From the start of this decade to its end, the world’s data will increase 50 times over.

̽��ֱ��basic building blocks of electronic devices, such as the transistor, work by moving packets of charge around a circuit. A single unit of charge is an electron, and its movement is governed by semiconductors, commonly made from silicon. But technology based on these principles is now reaching a point where it cannot get much smaller or faster. A paradigm shift is due.

“There have been many failed attempts to oust silicon from its predominance,” reflects Professor Mark Blamire, Head of Materials Science at Cambridge. “Something has to be done because the technology can’t be scaled to smaller sizes for very much longer. It’s already a major source of power consumption. There’s no obvious competitor, so in a sense the opportunity is there.”

Blamire and his colleague Dr Jason Robinson are leading several major programmes investigating one such competitor, known as superconducting spintronics.

̽��ֱ��launch of a UK-based programme last year provoked excitement within the scientific community. “Cambridge Uni spins up green and beefy supercomputer project,” announced British tech site ̽��ֱ��Register, for example. One reason in particular is because superconducting spintronics might address the eye-watering energy consumption of the huge server farms that handle internet traffic. Data centres account for 3% of the world’s electricity supply and about 2% of greenhouse gas emissions.

̽��ֱ��project combines two phenomena: superconductivity and spin. Superconductivity refers to the fact that at low temperatures some materials carry a charge with zero resistance. Unlike, for example, copper wires, which lose energy as heat, superconductors are therefore extremely energy efficient.

‘Spin’ is the expression for electrons’ intrinsic source of magnetism. Originally it was thought that this existed because electrons were indeed spinning, which turned out to be wrong, but the name stuck, and it is still used to describe the property in particles that makes them behave a bit like tiny bar magnets. Like a magnet, this property makes the electrons point a certain way; the spin state is therefore referred to as ‘up’ or ‘down’.

Researchers have been using the magnetic moments of electrons to store and read data since the 1980s. At their most basic, spintronic devices use the up/down states instead of the 0 and 1 in conventional computer logic.

Spintronics could also transform the way in which computers process information. ̽��ֱ��researchers envisage that instead of the devices moving packets of charge around, they will transmit information using the relative spin of a series of electrons, known as a ‘pure spin current’, and sense these using magnetic elements within a circuit.

By eliminating the movement of charge, any such device would need less power and be less prone to overheating – removing some of the most significant obstacles to further improving computer efficiency. Spintronics could therefore give us faster, energy-efficient computers, capable of performing more complex operations than at present.

To generate large enough spin currents for memory and logic devices, significant charge is required as an input, and the power requirements of this currently outweigh many of the benefits. Using a superconductor to provide that charge, given its energy efficiency, would present a solution. But the magnetic materials used to control spin within spintronic devices also interfere with superconductivity.

This problem was thought insurmountable until, in 2010, Robinson discovered how to combine superconductors and spintronics so that they can work together in complete synergy. His team added an intervening magnetic layer (a material called holmium). By using this interface, they were able to preserve the delicate balance of electron pairing that’s needed to achieve superconductivity, but still managed to create a bias within the overall spin of the electrons.

This, explains Robinson, “created a marriage that opens up the emerging field of superconducting spintronics.” Over the next five years, he and Blamire developed the field, and last year were awarded a major grant from the Engineering and Physical Sciences Research Council: “To lead the world in understanding the coupling of magnetism and superconductivity to enable future low energy computing technologies.” Robinson has since been awarded a second grant with Professor Yoshi Maeno, from the ̽��ֱ�� of Kyoto, to broaden materials research on superconducting spintronics.

Although still at an experimental stage, the project – which includes collaborators from Imperial College London, ̽��ֱ�� College London and Royal Holloway London – is tackling questions such as how to generate and control the flow of spin in a superconducting system. And its scope is already expanding. “We have found more ways of achieving what we are trying to do than we originally dreamed up,” Robinson says.

One example involves making potentially innovative use of superconductivity itself. In ‘conventional’ spintronics, spin is manipulated through the interactions between magnetic materials within the device. But Blamire has found that when a superconductor is placed between two ferromagnets, its intrinsic energy depends on the orientation of those magnetic layers. “Turning that on its head, if you can manipulate the superconducting state, you can control the orientation of the magnetic layers, and therefore the spin,” he says.

Meanwhile, Robinson has led a study that for the first time enabled graphene, a material already recognised for its potential to revolutionise the electronics industry, to superconduct. This raises the possibility of using this extraordinary material, and other two-dimensional materials like it, in superconducting spintronics.

Although approaches like this are still being tested, Blamire says that by 2021 the team will have developed sample logic and memory devices that fuse superconductivity and spin. These proof-of-concept models could, perhaps, be incorporated into a new type of computer processor. “It would be a huge step to get from there to a device that could be competitive,” he admits. “It’s not necessarily difficult, but it would require considerable investment.”

̽��ֱ��project is set up to enable industrial collaboration in the years to come. A key partner is the Hitachi Lab in Cambridge, while the project’s advisory board also features representatives from the Cambridge-based semiconductor firm ARM, and HYPRES, a digital superconductor company in the USA.

Robinson points out that the UK – and Cambridge in particular – has historical strengths in research into superconductivity and spintronics, but adds that a “grand challenge” has long been needed to focus academic investigation on a meaningful partnership with industry.

Leading low-energy computing into a post-semiconductor age is certainly grand. Silicon’s domination, after all, stretches from its eponymous valley in California, to a fen in Cambridge, a gulf in the Philippines and an island in Japan.

Can the unlikely – not to say still primitive – marriage of spintronics and superconductivity really replace an electronic empire on which the sun never sets? “I suspect people had similar questions at the dawn of the semiconductor,” Robinson observes. “One shouldn’t lose sight of what we are doing here. We aren’t just trying to do something better; we are offering something entirely different and new.”

Electron ‘spin’ could hold the key to managing the world’s growing data demands without consuming huge amounts of energy. Now, researchers have shown that energy-efficient superconductors can power devices designed to achieve this. What once seemed an impossible marriage of superconductivity and spin may be about to transform high performance computing.

One shouldn’t lose sight of what we are doing here. We aren’t just trying to do something better; we are offering something entirely different and new.

Jason Robinson

Creativity103

Spinning top

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

Yes

Licence type:

Attribution-ShareAlike

Cambridge to research future computing tech that could “ignite a technology field”

tdk25 — Thu, 14 Apr 2016 23:01:34 +0000

A project which aims to establish the UK as an international leader in the development of “superconducting spintronics” – technology that could significantly increase the energy-efficiency of data centres and high-performance computing – has been announced.

Led by researchers at the ̽��ֱ�� of Cambridge, the “Superspin” project aims to develop prototype devices that will pave the way for a new generation of ultra-low power supercomputers, capable of processing vast amounts of data, but at a fraction of the huge energy consumption of comparable facilities at the moment.

As more economic and cultural activity moves online, the data centres which house the servers needed to handle internet traffic are consuming increasing amounts of energy. An estimated three per cent of power generated in Europe is, for example, already used by data centres, which act as repositories for billions of gigabytes of information.

Superconducting spintronics is a new field of scientific investigation that has only emerged in the last few years. Researchers now believe that it could offer a pathway to solving the energy demands posed by high performance computing.

As the name suggests, it combines superconducting materials – which can carry a current without losing energy as heat – with spintronic devices. These are devices which manipulate a feature of electrons known as their “spin”, and are capable of processing large amounts of information very quickly.

Given the energy-efficiency of superconductors, combining the two sounds like a natural marriage, but until recently it was also thought to be completely impossible. Most spintronic devices have magnetic elements, and this magnetism prevents superconductivity, and hence reduces any energy-efficiency benefits.

Stemming from the discovery of spin polarized supercurrents in 2010 at the ̽��ֱ�� of Cambridge, recent research, along with that of other institutions, has however shown that it is possible to power spintronic devices with a superconductor. ̽��ֱ��aim of the new £2.7 million project, which is being funded by the Engineering and Physical Sciences Research Council, is to use this as the basis for a new style of computing architecture.

Although work is already underway in several other countries to exploit superconducting spintronics, the Superspin project is unprecedented in terms of its magnitude and scope.

Researchers will explore how the technology could be applied in future computing as a whole, examining fundamental problems such as spin generation and flow, and data storage, while also developing sample devices. According to the project proposal, the work has the potential to establish Britain as a leading centre for this type of research and “ignite a technology field.”

̽��ֱ��project will be led by Professor Mark Blamire, Head of the Department of Materials Sciences at the ̽��ֱ�� of Cambridge, and Dr Jason Robinson, ̽��ֱ�� Lecturer in Materials Sciences, Fellow of St John’s College, ̽��ֱ�� of Cambridge, and ̽��ֱ�� Research Fellow of the Royal Society. They will work with partners in the ̽��ֱ��’s Cavendish Laboratory (Dr Andrew Ferguson) and at Royal Holloway, London (Professor Matthias Eschrig).

Blamire and Robinson’s core vision of the programme is “to generate a paradigm shift in spin electronics, using recent discoveries about how superconductors can be combined with magnetism.” ̽��ֱ��programme will provide a pathway to making dramatic improvements in computing energy efficiency.

Robinson added: “Many research groups have recognised that superconducting spintronics offer extraordinary potential because they combine the properties of two traditionally incompatible fields to enable ultra-low power digital electronics.”

“However, at the moment, research programmes around the world are individually studying fascinating basic phenomena, rather than looking at developing an overall understanding of what could actually be delivered if all of this was joined up. Our project will aim to establish a closer collaboration between the people doing the basic science, while also developing demonstrator devices that can turn superconducting spintronics into a reality.”

̽��ֱ��initial stages of the five-year project will be exploratory, examining different ways in which spin can be transported and magnetism controlled in a superconducting state. By 2021, however, the team hope that they will have manufactured sample logic and memory devices – the basic components that would be needed to develop a new generation of low-energy computing technologies.

̽��ֱ��project will also report to an advisory board, comprising representatives from several leading technology firms, to ensure an ongoing exchange between the researchers and industry partners capable of taking its results further.

“ ̽��ֱ��programme provides us with an opportunity to take international leadership of this as a technology, as well as in the basic science of studying and improving the interaction between superconductivity and magnetism,” Blamire said. “Once you have grasped the physics behind the operation of a sample device, scaling up from the sort of models that we are aiming to develop is not, in principle, too taxing.”

A Cambridge-led project aiming to develop a new architecture for future computing based on superconducting spintronics - technology designed to increase the energy-efficiency of high-performance computers and data storage - has been announced.

Superconducting spintronics offer extraordinary potential because they combine the properties of two traditionally incompatible fields to enable ultra-low power digital electronics

Jason Robinson

10515 images via Pixabay

Growing quantities of data storage online are driving up the energy costs of high-performance computing and data centres. Superconducting spintronics offer a potential means of significantly increasing their energy-efficiency to resolve this problem.

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

Yes