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Home » Page 1531

Jostling balls reveal secrets of ultrathin films

Depositing extremely thin crystalline layers of different materials on a substrate – a process known as “epitaxy” – is key to the manufacture of semiconductor devices. But physicists have long been puzzled as to why some materials form flat ordered layers, whereas others grow as rough mound-like structures. Although researchers have created models of epitaxy that have helped the microelectronics industry, it has proved impossible to see how individual atoms move from site to site along a surface while forming a layer because the atoms are so small and move so fast.

Now, however, Itai Cohen and colleagues at Cornell University in the US have gained key insights into epitaxy by creating crystalline layers made of “colloidal” particles, which are bigger than atoms and so move much more slowly. They did this by bonding a closely packed layer of plastic balls 1 µm in diameter onto a flat substrate, which was then submerged in an aqueous solution of the balls. These balls were free to sediment onto the crystalline surface, where they slowly formed a thin layer.

In order to simulate the attractive interaction that causes atoms to crystallize into layers, the team then added much smaller polymer chains to the mixture, which coil up into spheres with a diameter of about 100 nm. Both the polymer spheres and the larger plastic balls are jostled about by random thermal fluctuations in the water (Brownian motion). But when two plastic balls come to within about 100 nm of each other, the polymer chains can no longer fit between them. Because there are no polymers between the balls to push them apart, the balls start to close in on each other – an imbalance that looks like a short-range attractive force.

Balls in motion

The team took a series of optical micrographs of the surface over several days, combining them to create a “movie” that shows how the plastic balls move (see above). The data reveal that when individual spheres land on the surface they move around randomly. But if the spheres get close to each other, they can coalesce to form a crystalline “island” that can grow by attracting other spheres.

In an ideal world, these islands would grow to cover the entire substrate, while remaining just one sphere thick. In practice, however, spheres tend to land on top of an existing island – and if these spheres cannot move over the edge of the island and onto the substrate, then the island will turn into a mound. Understanding and controlling the processes that cause such “step-edge barriers” are crucial to developing techniques for creating perfectly flat films.

As the interaction between atoms can extend out several atomic radii, atoms at an edge of a mound end up feeling an overall inward pull that keeps them on the island. However, the bonds between the plastic balls in the Cornell team’s model system are much shorter (relative to the ball’s radius) and the physicists did not expect to see such a barrier. But they did, which inspired the team to study the barrier using optical tweezers to place a sphere near a step edge and watching what happened next.

The Cornell team worked out that a sphere travelling across a step edge to the nearest lattice site has to move three times further than a sphere moving to a neighbouring site in any other direction. Because the motion of the spheres is described by a random walk, travelling over a step edge can take up to nine times longer than moving in another direction – which means that a sphere is more likely to remain on an island than leave it.

Cohen told physicsworld.com that such diffusion-related effects have not, as far as he is aware, ever been considered in models of atomic epitaxy, but they could be relevant because atoms are jostled about on a substrate by lattice vibrations. As a result, atoms could be “doubly cursed” when it comes to processes that work against the formation of perfectly flat films.

Biasing a random walk

On a more positive note, Cohen says that films of both spheres and atoms could be smoothed out by biasing the direction of diffusion. In the case of the spheres, this could be done by simply increasing the density mismatch between the particles and the fluid and letting gravity do the job. It may be possible to do the same for atoms by applying electric fields.

Other phenomena that could be studied using the spheres include surface reconstruction – a distortion of the surface lattice that often occurs when the film and substrate are different materials. This could be simulated by using two different-sized spheres for the substrate and film – something that the team is now investigating.

Cohen also points out that crystals made of micron-sized spheres are interesting in their own right. Indeed, they can be made with lattice constants on par with optical wavelengths. This means that they could find uses as photonic crystals in optical telecommunication devices.

The work is reported in Science 327 445.

Dreaming of Northern Lights

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Aurora Borealis over Tromsø, Norway photo: Bjørn Jørgensen

By James Dacey

There are occasions during my reporting when I come across jobs that make me really quite envious…

Siobhan Logan, a writer in the UK, was given the opportunity to travel to northern Norway where she meet a group of auroral scientists and local reindeer herders, before documenting her adventures in writing and film.

Her work will feature as part of an upcoming show at the National Space Centre in Leicester that will feature poetry, physics and film inspired by Aurora Borealis, or the Northern Lights.

“For a writer, it was such an inspiring place. I was interested in the myths indigenous Arctic people have created about the Northern Lights but also what the scientists can tell us about the aurora. I came back with my head full of the creatures, characters and stories of the north,” says Logan of her experience.

The spectacular natural light displays of Aurora Borealis have always been a regular feature in the myth and folklore of northern peoples, like the Cree groups of northern America who describe this phenomenon as the “dance of the spirits”.

In recent years, the popular author Philip Pullman has brought the magic of auroras to a new generation of children through the His Dark Materials trilogy – a fantasy series tracking the adventures of bright young girl Lyra Belacqua as she passes through the aurora into a parallel universe.

Logan’s trip was made possible by sponsorship from the University of Leicester, which has strong links with a research base in Tromsø. This facility is owned by EISCAT – a project designed to study the interaction between the Sun and the Earth as revealed by disturbances in the magnetosphere and the ionised parts of the atmosphere.

Stan Cowley of the Radio & Space Plasma Physics Group at the University describes why he is excited by the project. “Science may tell us of the mechanisms of the auroras, but another language is required to express our reaction to the sight of flickering lights over frozen landscapes.”

The performance at the National Space Centre will takes place on February 23 at 7.30 pm – tickets are free but you need to book in advance.

Bright colour-changing skins

Researchers at Philips, the Dutch electronics giant, have designed a novel type of electronic paper that can change colour at the flick of a switch and does not require backlights. Philips says that the e-paper could be used for digital signs, enabling shop displays to be changed rapidly, and then retained without consuming too much energy. It is also seeking to develop colour-changing “skins” for products like mobile phones and handheld games consoles.

Electronic paper looks like conventional paper but because it reflects ambient light it does not need a backlight like conventional liquid crystal displays. The technology is already found in electronic book readers, such as Amazon’s Kindle, which have a matt appearance that is finally beginning to resemble the pages of a pocket novel. Such devices typically consist of electrically charged particles encapsulated between two electrodes, at least one of which is transparent. The particles are located at pixel sites, which can be controlled by applying an external electric field, in a process called electrophoresis.

Turning the page

In a standard book reader, the colour of each pixel can be alternated between two colours of choice – usually black and white – by flipping the polarity of pixels with an applied electric field. In this way, the pattern of black pixels on a screen forming the words of a book can be altered by pressing a button whenever a reader “turns” a page.

The Philips researchers instead apply a voltage across two electrodes on the face of the e-paper, rather than “into” the display as seen in conventional “top-down” electrophoresis. This “in-plane” electrophoresis means that they can combine different-coloured pigments in each pixel and use a third electrode to control how these particles spread across the display, which in turn dictates the saturation or shade of each colour.

In their design, all the different coloured pigments – cyan, magenta, yellow and black – can be stacked away in the corner of each pixel site leaving a transparent display. “It boils down to: where can we hide the coloured particles?” explained Kars-Michiel Lenssen, who is leading the Philips team developing these devices.

Lenssen’s team created a 10 µm thick display filled with magenta pigment to demonstrate the principle of the new technology. It reflects 80% of incoming light in the clear state, when the pigment is “hidden” in the corner. When the pigment is spread out, it reflects around 10% of the incoming light – at a wavelength of 570 nm. Importantly, the device has a contrast of 25:1 whereas previous e-papers, which use top-down electrophoresis, have only managed up to 8:1.

Reflecting on progress

Jurgen Daniel of the Palo Alto Research Centre (PARC) points out that similar electronic skin products have already been developed by Hewlett-Packard and Kent Research, based on LCD technology. He is impressed, however, with the progress Philips has made in this research. “For full-colour electronic paper, the reflectance values sound promising but the required stacking of layers has some challenges.”

Lennsen and his team intend to develop their work alongside other researchers in related fields. “Because Philips is not a chemical company, we will not produce the electrophoretic inks by ourselves,” he said. “We have demonstrated the feasibility of the concept with a few colours and do not expect major issues for a chemical company to develop similar inks in other colours.”

Details of this ongoing research project are published in Journal of the Society of Information Display (18 1–7).

Quantum computer takes on quantum chemistry

The hydrogen molecule may be the simplest of all two-atom systems, but chemists have had to work very hard to calculate its properties from first principles using quantum mechanics. Now, however, a team of physicists and chemists in the US and Australia has for the first time calculated the molecule’s energy levels using a primitive quantum computer that consisted of a pair of entangled photons.

Quantum computers are very different from classical computers, which store and process information as bits that can have one of two states – “0” or “1”. A quantum computer, in contrast, exploits the ability of quantum particles to be in a “superposition” of two or more states at the same time. These quantum bits – or qubits – can also be entangled, whereby a measurement of one qubit instantly reveals the state of the other.

Although physicists have struggled to create even the simplest quantum computers, such devices could, in principle, outperform classical computer on some tasks. Quantum chemistry is one field that could benefit from quantum computers because calculations involving molecules tend to require computing resources that increase exponentially with the number of atoms involved.

Bonding and anti-bonding states

The new work has been carried out by Alán Aspuru-Guzik and colleagues at Harvard University’s Department of Chemistry, working with Andrew White and his team at the University of Queensland. Each of the two entangled photons in their computer is a qubit, in which “0” and “1” correspond to the horizontal and vertical photon polarization states respectively. One of the entangled photons represents the hydrogen molecule. This photon’s two states correspond to the molecule’s bonding and anti-bonding states. The other photon represents a bit of the binary number corresponding to the total energy of the molecule.

The researchers calculated the energy of the molecule using what is known as an iterative phase estimation algorithm (or IPEA). An iteration begins with a pair of entangled photons being created by shining light at a non-linear crystal through the process of “spontaneous parametric down-conversion”. The photon representing the molecule is then passed through a series of optical components that simulate the interactions between nuclei and electrons that define the energy (or Hamiltonian) of the hydrogen molecule. The result is a change in the quantum state of the qubit – and this time evolution (or phase shift) is related to the energy of the molecule.

The phase shift is determined by recombining the entangled photons in a beam splitter and then measuring the value of the photon that represents the energy bit. Because this process is prone to the occasional error, it is repeated about 30 times to decide whether the polarization is more likely to be “0” or “1”.

This value is one bit of the binary number that defines the energy of the molecule. The bit is then fed back into the optical system, which is adjusted before the process is repeated to give the second bit of the energy value – and so on.

20-bit binary number

The process is done 20 times to create a 20-bit binary number that represents the energy of the hydrogen molecule to a precision of about one part per million. This energy is for a fixed inter-atomic separation, so the calculation must be repeated for a number of different separations to find the minimum energy state.

Using the technique, the team obtained an energy-versus-separation curve that agrees exactly with that obtained by a classical computer. This was done for the lowest energy state of the molecule as well as three higher energy states.

The result was, however, obtained with some help from a classical computer, which was used to work out the initial quantum state of the molecule (prior to applying IPEA) and also in some parts of the iteration itself. Performing these functions on a quantum computer will be a major challenge, according to the researchers.

Baby step

Aspuru-Guzik described the two-qubit calculation as a “baby step forward,” and added that a 128-qubit system would be needed to work out the energy levels of a simple molecule such as water. He told physicsworld.com that his group is planning to work with the Australians as they create successively larger quantum devices. He also said that he is looking for research partners who could implement the calculation in quantum computers based on trapped ions and/or superconducting quantum bits.

Jeremy O’Brien at the University of Bristol in the UK described the calculation as “an extremely exciting application of quantum computing”. Regarding the use of a classical computer, O’Brien explained that physicists “can’t leap forward and do everything at once”.

The work is described in Nature Chemistry.

Fear grips Iranian academics

“We are living in an atmosphere of fear,” says Reza Mansouri, a cosmologist at Sharif University in Tehran, referring to academic life in the Iranian capital in the wake of the assassination of a fellow physicist last Tuesday.

Masoud Alimohammadi, a 50-year-old physics professor at Tehran University, was killed by a remote-controlled bomb attached to the side of a motorcycle. The bomb was detonated as he left his house for work last Tuesday morning.

Reports by the Iranian state media have blamed the US and Israel for the attack, a claim that the US has since described as “absurd”.

Examination of Alimohammadi’s publication record reveals that he was not an applied nuclear physicist as the Iranian state media had claimed, but a mathematical physicist working in quantum mechanics and field theory. He had published more than 50 papers and had recently specialized in theories of dark energy. His last paper was entitled “Remarks on generalized Gauss-Bonnet dark energy”, which appeared in Physical Review D last March (Phys. Rev. D 79 063006).

“None of his work has anything remotely to do with nuclear weapons so I wonder why they are calling him a nuclear scientist and suggesting that the US or Israel may have bumped him off,” says Subir Sarkar, a theoretical physicist at the University of Oxford in the UK.

Not a political figure

Alimohammadi was one of the first four physicists to complete his doctorate in its entirety within Iran, as the nation did not run PhD programmes before the Islamic Revolution of 1979. He did his PhD at Sharif University of Technology, having been offered a place by Mansouri. “Alimohammadi was a practising Muslim and was engaged in activities linked to the [Iranian] cultural revolution,” recalls Mansouri.

The rhetoric of the authorities in relation to the West is getting more hard-line and I am certainly very concerned for independently minded academics Najib Ghadbian, University of Arkansas

Although Mansouri adds that Alimohammadi was not a political figure, other reports – including the BBC’s – say that his name was among 420 academics who signed a letter in support of the opposition at the presidential elections last June.

University campuses have become increasingly politicized since the June elections, which sparked Iran’s worst unrest since the cultural revolution – the period in the 1980s that followed the Islamic Revolution. Reuters news agency reported that riot police surrounded Tehran University, where Alimohamadi worked, on 8 December when a large state rally was being held there to try to prevent opposition protests.

Najib Ghadbian, a political scientist at the University of Arkansas and author of Democratization and the Islamist Challenge in the Arab World, describes the overall situation in Iran as “very tense”, since the elections. “The rhetoric of the authorities in relation to the West is getting more hard-line and I am certainly very concerned for independently minded academics,” he says.

Nuclear tensions

Meanwhile, this weekend diplomats from six nations, including the US and the UK, met to discuss further possible UN sanctions on Iran’s nuclear ambitions. Ghadbian believes that meetings like this one are serving only to strengthen the anti-Western rhetoric of the Ahmadinejad regime, making the situation even more perilous for academics in Iran.

“What politicians in the West fail to understand is that support for a nuclear programme is widespread in Iran, even among those who do not support the presiding regime,” he says.

The current picture of Iran stands in stark contrast to the country experienced by João Magueijo, a cosmologist at Imperial College, London, who spent time in working in Iran in 1999. “I was very impressed by the universities and their huge campuses, and had a lot of fun with the students there,” he says.

“Above all in academia I found complete integration between seriously religious people and effective atheists. They exchanged jokes about each other’s options in the light tone only possible under real tolerance (and obviously in contrast with the law).”

The funeral of Masoud Alimohammadi took place in Tehran last Thursday and The Times reported that hundreds of government loyalists surrounded the body as it was carried from the physicist’s home in the north of the city. Further tributes are expected to follow once 40 days have passed since the death, in keeping with Islamic tradition.

Newton's apple – the birth of a physics legend

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Home to a famous apple tree

By Hamish Johnston

In 1666 a young Isaac Newton was waiting out the plague in his mother’s garden in Lincolnshire when an apple fell from a tree. Newton wondered why such bodies always moved downwards, rather than sideways or upwards – and the theory of universal gravitation was born.

Or so goes the most famous anecdote in the history of physics…a story that Newton himself appears to have repeated often in later life, but never wrote down.

Now you can read the earliest known account of this tale, written by William Stukeley who was a friend of the great physicist.

Stukeley’s Memoirs of Sir Isaac Newton’s Life is available on the Royal Society’s Turning the Pages gallery of manuscripts – created to celebrate the 350th anniversary of the society. Both Newton and Stukeley were Fellows of the Royal Society.

The site offers the manuscript in three different formats but I was only able to view the most basic version – if you have the same luck, just left-click on a page for large and very readable version. The apple story can be found on pages 42–43 of the work.

Quiz of the year winner

By Margaret Harris

Congratulations to Dr Cristina Lazzeroni of Birmingham University for winning Physics World‘s 2009 Quiz of the year, which — as per tradition — looked back on a year of celebrations, retractions, notable discoveries and quotable personalities in the world of physics.

In addition to the everlasting glory of victory, Dr Lazzeroni will also receive a cheque for £50, which I suspect will just about cover a slap-up dinner in the UK’s second-largest city.

If you missed out on the quiz this year, it’s partly my fault: I got caught up in the end-of-the-year rush and forgot to get it posted online. I’ll try to rectify that soon, but please be advised that the prize itself is now closed to new entries.

If you’ve already tried the quiz, you can check your answers below:

(more…)

Newton’s idea spotted in reflected neutrons

An optical effect first proposed by Isaac Newton has been observed in matter for the first time. The discovery is yet another affirmation of wave–particle duality – one of the cornerstones of quantum mechanics. The breakthrough is also the first published science to emerge from a £200m neutron source recently opened in the UK.

Newton predicted in the 17th century that a beam of light reflected at a glass-vacuum surface should undergo a minuscule lateral shift. He was arguing that wavefronts, having reached the vacuum, should “slide” a short distance along the interface before re-emerging and reflecting back into the glass. Given the tiny scale of this effect, however, it was not until 1947 that it was first observed experimentally by the physicists F Goos and H Hänchen at the State Physical Institute in Hamburg, Germany.

Case closed? Well not quite because, as all physicists are taught in high school, the distinction between waves and particles is not as clear-cut as common sense might suggest. Due to the quantized nature of energy, light can sometimes behave as if it were composed of particles, and particles can behave as if they were waves. Now, a group of researchers led by Rob Dalgliesh and Sean Langridge at the ISIS facility and Victor de Haan from the Delft University of Technology (Netherlands) have finally completed the picture by demonstrating the so-called Goos-Hänchen effect with neutrons.

Altered polarization

The researchers exploit the fact that a neutron possesses a magnetic moment that can be represented by a wavefunction known as a “spinor” comprising both up-spin and down-spin components. Theorists have calculated that the Goos-Hänchen shift should affect the up and down wave functions to differing extents, meaning that the overall polarization of a beam of neutrons should be altered by the act of it reflecting in a mirror. The outcome is that during reflection the up and down spin states should be split in space and time.

Dalgliesh and Langridge, working with their colleagues in the Netherlands, have designed an instrument capable of detecting subtle differences in polarization over a tiny area. They use this instrument, named “Offspec”, to record a spatial “splitting” of the neutron wavefunctions of up to 100 nm, which also corresponds to a time delay of the order 0.1 µs. The results were obtained at the second target station at the ISIS neutron source, which began its science operations last August, providing researchers with access to seven new state-of-the-art instruments.

Langridge tells physicsworld.com that the new facility has enabled a “step change” in the applicability of neutron scattering to nanoscience. “There are many exciting projects right across the scientific and engineering disciplines that will benefit from the improved capabilities and resolution”. What is more, he believes that the data from this latest research highlights the sensitivity of the neutron technique and may be technologically relevant to the improvement of neutron waveguides and, looking further, to next generation electronics.

This research is published in Physical Review Letters.

Calculations point to massive quark stars

For a large star, death is a bit of a squeeze. Once its nuclear fuel is spent, its core collapses, sparking a dramatic supernova explosion that blasts away the outer layers. The body left is a cold, tightly packed sphere called a neutron star, which, if massive enough, makes the ultimate collapse to a black hole.

The huge pressures inside neutron stars mean that all electrons and protons have joined so only neutrons remain. Near the centre, according to theory, these neutrons sometimes decompose into a sea of quarks, or so-called strange quark matter. A recent theory implies that this matter could form a stable ground state of nuclear matter – suggesting the existence of standalone “quark stars”.

Evidence for quark stars is in short supply, with only a handful of observed candidates. Yet new calculations by an international group of theorists paint a better picture of the nature of quark stars, and suggest that they might be easier to spot than previously thought. “The main conclusion of our work is that there is a clear signature for the possible detection of quark stars – and thus stable strange quark matter,” says author Aleksi Vuorinen of the University of Bielefeld in Germany.

Applying perturbation theory

Vuorinen joined forces with Aleksi Kurkela at ETH Zurich in Switzerland and Paul Romatschke at the University of Washington in Seattle to examine how the pressure of strange quark matter depends on its density – a relationship described by the star’s “equation of state”. Physicists have looked at this before, but only using highly simplified models of quark interactions. Instead, Vuorinen’s group has employed perturbation theory – a technique that approximates mathematical solutions in stepwise fashion, which on the whole is far more accurate.

The result may surprise other physicists. Current thinking has it that quark stars should be smaller than neutron stars, and indeed that compact stars above a certain size – typically about twice the mass of our Sun, or two solar masses – must be pure neutron stars with no quark core. However, Vuorinen’s group conclude almost the opposite: that the biggest quark stars can be larger than neutron stars, perhaps up to 2.5 solar masses. In other words, as Vuorinen points out, the detection of a compact star with a mass near that limit would be a “strong indication” of a quark star.

Such a detection would be of great interest to astrophysicists, because it would open a window onto the properties of strange quark matter. Unlike hot quark matter, or a “quark gluon plasma”, which can be studied at particle accelerators like the Large Hadron Collider at CERN, strange quark matter is impossible to create in the lab at present.

Controversial conclusions

Thomas Schaefer, a quark physicist at North Carolina State University in the US, thinks it is a “very interesting paper”, even though he says that some of the conclusions will be controversial. “I actually tend to agree with what the authors say [on the potential size of quark stars],” he adds.

But others are not so sure. Mark Alford at Washington University in St Louis, Missouri, notes that the perturbation theory used by Vuorinen’s group is only truly accurate when the quarks are millions of times denser than in real neutron stars. “When they talk about neutron stars, they are extrapolating their calculation into a region where it is not reliable,” he says. “However, this is an improvement on what was available beforehand…this paper is actually a real step forwards.”

The study is available as a preprint at arXiv.

Electric fields control spin currents

Physicists in France, Germany and the UK claim to be the first to control the polarization of a spin current by applying an electric field across an insulator. The technique requires much less energy than previous schemes for flipping spin, and could play an important role in the development of spintronics technology and ultimately smaller and more efficient electronic devices.

Spintronics is a relatively new area of research that exploits the spin of an electron as well as its charge. The spin can either be “up” or “down”, and this property could be used to store and process information in spintronic devices. Such circuits could be smaller and more efficient than conventional electronic circuits – which rely on switching charge – because switching spins from up to down could be done using very little energy, at least in principle.

For such devices to be practical, however, physicists need to work out a way to flip spins by applying electric fields, rather than magnetic fields. This is because magnetic fields are much more costly in terms of space and energy. Physicists have had some success in controlling spin by driving large currents through a magnetic conductor, but this is also very energy intensive.

Now, a team led by Agnès Barthélemy of CNRS/Thales Research and Technology and Université Paris-Sud in France has demonstrated electric-only control in a hybrid material made by coupling a ferroelectric to a ferromagnet. A ferroelectric is a material that contains tiny domains of electrical polarization, analogous to magnetic domains in a ferromagnet. This new result is exciting because it demonstrates a new type of magnetoelectric coupling, different to that which exists in the widely known composite materials, says team member Manuel Bibes, also at CNRS/Thales.

Tunnel magnetoresistance

The researchers began by making tiny tunnel junctions that combine two ferromagnetic electrodes – iron and the ferromagnetic oxide LSMO – separated by a layer of ferroelectric barium titanium oxide (BaTiO3) just 1 nm thick. Six months ago, the same team showed that such ferroelectric tunnel barriers could produce giant electroresistance effects at room temperature (Nature 460 81). Now, Barthélemy and colleagues have measured the tunnel magnetoresistance (TMR) after orienting the ferroelectric polarization in the BaTiO3 tunnel barrier up or down by applying voltage pulses of around 1 V. TMR is a well known effect in which the tunnel resistance depends on the magnetic alignment of two ferromagnets.

The TMR was found to depend on the ferroelectric polarization, which, according to the researchers, indicates a change in the spin-polarization of the tunnel current. “To our knowledge, this is the first time that spin-polarization has been controlled by an electric field alone,” Bibes told physicsworld.com.

All spintronic effects, such as TMR and giant magnetoresistance, depend on the spin-polarization of the electrical current. Controlling the spin-polarization by electric fields in this way therefore potentially opens the way to controlling all spintronics devices by purely electric means.

Interplay at the interfaces

On a more fundamental level, the new work also emphasizes the interplay between ferroic materials at interfaces, explained Bibes. This could lead to a new generation of artificial materials that exploit giant interfacial phenomena. “More practically, the result could prove useful in reducing the write power in magnetic random access memories (MRAMs).”

The team, which includes scientists from the Laboratoire de Physique des Solides in Orsay, France, BESSY in Berlin, Germany, and the University of Cambridge in the UK, is now planning complementary experiments to further investigate the interface physics in the LSMO/BaTiO3/Fe samples. “In the longer term, we will probably extend our study to other interface systems,” added Bibes.

The work was published in Sciencexpress.

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