Self-destructive Effects of Magnetically-doped Ferromagnetic Topological Insulators

The discovery of “topologically protected” electrical conductivity on the surface of some materials whose bulk interior acts as an insulator was among the most sensational advances in the last decade of condensed matter physics—with predictions of numerous unusual electronic states and new potential applications. But many of these predicted phenomena have yet to be observed. Now, a new atomic-scale study of the surface properties of one of these ferromagnetic topological insulators reveals that these materials may not be what they had seemed. The research—conducted at the U.S. Department of Energy’s Brookhaven National Laboratory and published in the Early Edition of the Proceedings of the National Academy of Sciences—revealed extreme disorder in a fundamental property of the surface electrons known as the “Dirac mass.” Like the mass imparted to fundamental particles by their interactions with the recently confirmed Higgs field, Dirac mass results from surface particles’ interactions with magnetic fields. These fields are created by the presence of magnetic atoms substituted into the material’s crystal lattice to convert it into a ferromagnetic topological insulator.

To read the full article from CEMAG click here

Séamus Davis

Séamus Davis

 

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January 2015: Physics fun for the whole family at the kitchen

Story from the Lansing Star 1/09/2015

Physics fun for the whole family comes to Kitchen Theatre Company this month!   KTC collaborates with Xraise (the outreach arm of Cornell University’s Laboratory for Accelerator-Based Sciences and Eduction) and young actors from Running to Places Theatre Company to present two performances of the original musical, Physics Fair by Rachel Lampert and Lesley Greene. Performances are Saturday January 24th and Saturday, January 31st at 1:00 PM. Physics Fair is appropriate for ages five to ninety-five.

What do you do if your middle school is so ordinary, so humdrum, so boring that nothing ever changes? Even the school’s motto celebrates the fact that ‘one day’s like the other in every way!’ Well, if you are in Mr. Mundani’s (root word: mundane) sixth grade class, you stand up and ask for something new! You introduce the school’s first ever Physics Fair, promise not to ring the bell in the bell tower, and turn Mildweather Middle School upside down.

Physics makes the world go ’round, and Mildweather Middle School has a new curiosity for science that can’t be stopped. And after seeing the talented young cast, hearing the catchy songs and watching the astounding physics demonstrations, you and the young people in your life may find your lives changed, just like the Mildweather middle schoolers!

(from left to right) Standing - Erik Herman, Lora Hine, Joey Steinhagen, Lesley Greene. On stools - Caitlin Mallory, Erin Hilgartner, Christian Henry, Elisheva Glaser, Imri Leshed. On the floor - Kayla Markwardt, Lucian Mead-VanCort. Photo: Dave Burbank

(from left to right) Standing – Erik Herman, Lora Hine, Joey Steinhagen, Lesley Greene. On stools – Caitlin Mallory, Erin Hilgartner, Christian Henry, Elisheva Glaser, Imri Leshed. On the floor – Kayla Markwardt, Lucian Mead-VanCort. Photo: Dave Burbank

Physics Fair is written by Kitchen Theatre Company Artistic Director Rachel Lampert (book & lyrics) and Associate Producer Lesley Greene (music & lyrics). Lampert and Greene have collaborated on many musicals for young people, including Science Fair, Park Play, Winter Tales, Emmett & Ella’s Big Apple Escapade, and Fools! Schmools!  Kitchen Theatre Artistic Associate Emily Jackson directs, and the music director is Patrick Young. Lighting design is by Paul Radassao. Kitchen Theatre Company artistic interns Zoe Benditt and Jenni Kuhn serve as assistant directors.Playing Mildweather’s sixth graders are real-life middle and high school students Elisheva Glaser, Christian Henry, Erin Hilgartner, Imri Leshed, Caitlin Mallory, Kayla Markwardt, and Lucian Mead-VanCort. Their teacher, Mr. Mundani, is played by Joey Steinhagen, Artistic Director of Running to Places Theatre Company. Lesley Greene plays the school’s principal, Ms. Standard.Physics Fair is produced in collaboration with Lora Hine and Erik Herman of Xraise, the outreach arm of the Cornell Laboratory for Accelerator Based Sciences and Education (CLASSE). Hine and Herman designed and built the physics demos for Physics Fair, and they also make an appearance in the play! Cornell physicist Peter Wittich provided additional feedback about the science in the play. Funding was provided in part by a grant from the American Physical Society.
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January 2015: High-temperature superconductor ‘fingerprint’ found

Theorists and experimentalists working together at Cornell may have found the answer to a major challenge in condensed matter physics: identifying the smoking gun of why “unconventional” superconductivity occurs, they report in Nature Physics, published online Dec. 22.

Associate professor of physics Eun-Ah Kim led the way, joining forces with experimentalist J.C. Seamus Davis, the J.G. White Distinguished Professor of Physical Sciences in the College of Arts and Sciences. They have isolated a “fingerprint” that identifies specific fluctuations in electrons that force them into pairs, causing their host material, in this case, a high-temperature superconductor called lithium iron arsenic, to make way for free-flowing, resistance-free electron pairs.

Superconductivity overcomes the naturally occurring repulsion between electrons, quantified by Coulomb’s law, which normally prevents their pairing. In “conventional” superconductors – metals that allow electrons to flow without resistance at temperatures around 460 degrees below zero – there’s pretty good understanding of why superconductivity happens. In that case, electron pairing is driven by the exchange of vibrations in the material’s crystal structure, which become strong enough to overcome Coulomb repulsion. This mechanism only works in extremely cold temperatures in which electrons move very slowly.

To read the entire Cornell Chronicle article, click here.

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December 2014: The arXiv preprint server hits 1 million articles

The popular preprint server arXiv.org, where physicists, mathematicians and computer scientists routinely upload manuscripts to publicly share their findings before peer review, now holds more than 1 million research articles.

The repository, launched as an ‘electronic bulletin board’ in August 1991, just before the dawn of the World Wide Web, took 17 years to accumulate half a million manuscripts, but has taken just 6 more to double its holdings.

Researchers now submit around 8,000 articles to the arXiv each month — more than 250 a day, on average. The site’s administrators make the raw, non-peer-reviewed manuscripts available in batches after a brief quality-control check, such as a cursory glance for appropriateness by one of 130 volunteer moderators, and automated filtering to check for text overlap with existing papers.

The site reached more than 1 million papers on 29 December, after administrators returned from holidays and updated the server with manuscripts submitted after business hours on Christmas Eve (24 December).

Judging by the running count of articles currently displayed on the arXiv’s home page, the manuscript that bears the landmark 1-millionth identifier is ‘A well conditioned and sparse estimate of covariance and inverse covariance matrix using a joint penalty’, which was submitted at 7:34:19 GMT on 26 December by Ashwini Maurya of Michigan State University in East Lansing. But in fact, the site’s millionth article cannot be pinpointed so precisely, says arXiv founder Paul Ginsparg, a physicist at Cornell University in Ithaca, New York. The count is actually a slightly fuzzy estimate owing to the way submissions are indexed and because the occasional duplicate or junk submission creeps in — something that can now be spotted by screening software but was easier to miss in the early days of the site.

To read the entire Nature article, click here.

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December 2014: Instant-boot computers may soon be possible

WASHINGTON: Imagine a computer that starts instantly with the click of a button! A new device developed by researchers, including one of Indian-origin, may make this possible.

To encode data, today’s computer memory technology uses electric currents – a major limiting factor for reliability and shrinkability, and the source of significant power consumption.

If data could instead be encoded without current – for example, by an electric field applied across an insulator – it would require much less energy, and make things like low-power, instant-on computing a ubiquitous reality, researchers said.

A team at Cornell University led by postdoctoral associate John Heron has made a breakthrough in that direction with a room-temperature magnetoelectric memory device.

To read the entire Economic Times article, click here.

If data could instead be encoded without current – for example, by an electric field applied across an insulator – it would require much less energy, and make things like low-power, instant-on computing a ubiquitous reality, researchers said.

If data could instead be encoded without current – for example, by an electric field applied across an insulator – it would require much less energy, and make things like low-power, instant-on computing a ubiquitous reality, researchers said.A team at Cornell University led by postdoctoral associate John Heron has made a breakthrough in that direction with a room-temperature magnetoelectric memory device.

WASHINGTON: Imagine a computer that starts instantly with the click of a button! A new device developed by researchers, including one of Indian-origin, may make this possible.To encode data, today’s computer memory technology uses electric currents – a major limiting factor for reliability and shrinkability, and the source of significant power consumption.If data could instead be encoded without current – for example, by an electric field applied across an insulator – it wo ..

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WASHINGTON: Imagine a computer that starts instantly with the click of a button! A new device developed by researchers, including one of Indian-origin, may make this possible.To encode data, today’s computer memory technology uses electric currents – a major limiting factor for reliability and shrinkability, and the source of significant power consumption.If data could instead be encoded without current – for example, by an electric field applied across an insulator – it wo ..

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December 2014: Origami Engineering: The future of soft robotics unfolds

Applegate 12/22/14

Origami is inspiring a new research discipline in the engineering sector. The Japanese form of paper-folding, originally an ancient recreational artistic activity, has stepped into the modern age and is now being applied to the realisation of purposeful three-dimensional structures folded from a single flat sheet. Among other areas, this emerging practise is now benefiting robotic development.

Origami is particularly useful in the soft robotics field, where machines are built entirely with malleable materials for unique flexibility. In the past couple of decades, mathematicians and engineers have been pioneering the potential of paper-folding to construct objects that are capable of self-assembly and movement.

This has been influenced, in part, by structures seen in nature. The distinctive crease of the ‘Miura’ fold is a good example of this, as it mimics the organic design we see in a gathered plant bud as it unfolds and opens out, for instance. This intricate pattern is repeated across many other flowering plants and also in countless insects, like beetles. The Miura fold has been utilised, in origami engineering, because as a structural form it is especially flexible. Features including the ability to become very small (whilst retaining its core strength, thus making it difficult to damage), as well as being an easy fold to open and close, make the Miura a good option for soft robotics. However, origami has come a long way from hand-folding, as it would have traditionally been achieved, and there are now computer programs that aid the design process configuring an accurate fold pattern, without the need for manual input.

Using this principle, a team of researchers, engineers and computer scientists at the Wyss Institute, Harvard’s School of Engineering and Applied Sciences (SEAS) and the Massachusetts Institute of Technology (MIT) have built a robot that assembles itself into a complex shape in just four minutes and can move around without any human intervention, from a piece of paper. Prior to being folded, the flat panels are embedded with electronics and connected by hinges. The team also used materials that, when heated to 100 degrees Celsius, will activate the contraction and folding of the machine. Robert J. Wood,  Professor of Engineering and Applied Sciences at Harvard’s SEAS and a key contributor to the project, was recognised for his work in the development of biologically inspired robots earlier this year, being named one of fourteen ‘Emerging Explorers’ by the National Geographic Society. Of their recent success, he said “Getting a robot to assemble itself autonomously and actually perform a function has been a milestone we’ve been chasing for many years”.

Their findings are also helping to build research that could lead to several useful applications in the future. Firstly, the ‘origami robots’ can be controlled remotely so they could be used in environments that are, conceivably, too dangerous for people to go. Building shelters in conflict zones or much further a-field, placing satellites into space, are just two examples of how their autonomous assembly will assist us in the years to come.

Already origami engineering is making the idea of ‘search-and-rescue bots’ a real possibility. In its thin two-dimensional state and without hard edges, the robot can fit into tight spaces and then be deployed, again remotely. As Dr Jesse Silverberg, a Physics Graduate Student at Cornell University, explains “Imagine this: a building collapses, and you have a snake-like robot that can go into debris. And as it unfolds, it goes from a soft robot to a rigid barrier that could protect people. It folds one way to crawl into tight spaces and another way to become a protective barrier”.

Researchers are also investigating the capabilities of these bots on a minuscular scale, using the folding properties of DNA, to produce a range of tiny objects that could be used as a catalyst to administer medicine into the body. As motion becomes better established in origami robotics, we could find these ‘nanobots’ being tasked to crawl around our bodies, detecting and diagnosing any abnormalities they come across. Although, I’m not sure how well this particular application will be welcomed, thankfully it won’t happen anytime soon.

Origami is helping to reinvent the way engineers approach a problem and the experiment at Wyss Institute, has demonstrated its benefits in building machines that can interact with the environment around them, with fewer cost and time implications. For the most part it has already been well received. As Silverberg suggests “If you look up into space, or the operating room, you’re likely to see origami and it may one day save a life”. Concluding, “The bottom line is that the potential applications of paper folding are just really cool and I think it’s safe to say that the future is going to be awesome”.

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December 2014: ‘Text overlap’ clutters scientific papers, arXiv analysis finds

Computer text analysis of a huge database of scientific papers shows a large amount of “text overlap,” where authors use text from previous papers of their own and others, not always with attribution. This is not necessarily good or bad, Cornell researchers say.

“Our first goal was to characterize the accepted practice, not to be judgmental,” said Paul Ginsparg, professor of physics and information science and founder of the online arXiv collection of scientific papers, now maintained by Cornell University Library. The analysis was conducted on thousands of papers in the arXiv. Ginsparg and Cornell graduate student Daniel Citron reported their study in the Dec. 8 online edition of the Proceedings of National Academy of Sciences.

“While it is technically plagiarism, which more generally is stealing of ideas,” Ginsparg said, “it’s a benign form in the sense that most of it cites the source (at least somewhere in the article), and many authors have rationales for the practice.” Many readers find the reuse of text “an annoyance and a distraction,” he added, and some worry that it wastes space online and in print journals.

Sometimes the copied text is a description of experimental apparatus or procedures. Mathematicians often repeat well-known theorems that underlie their arguments. Many authors reuse material from their own previous papers about the same line of research, and a Ph.D. candidate’s final thesis may pull in material from papers the student had published along the way. An amusing sidelight is the copying of acknowledgements with new names inserted, possibly because authors think what they are using is a standard format.

To read the entire Cornell Chronicle, click here.

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December 2014: New teaching model a ‘game changer’

By Linda B. Glaser

College of Arts and Sciences Medium

12/18/14

Hundreds of students have just completed the first transformed courses in the College of Arts and Sciences’ Active Learning Initiative (ALI), part of a strategic effort by the College to embrace engaged learning models and emerging technologies. The ALI five-year pilot project, funded by Alex and Laura Hanson, Class of 1987, implements a deliberate practice model advocated by Nobel Laureate Carl Wieman to enhance the performance and learning of all students.

“Because the College of Arts and Sciences teaches foundational courses that all undergraduate students throughout the university take, we have the unique opportunity to impact undergraduate education throughout Cornell with this initiative,” says Gretchen Ritter, The Harold Tanner Dean of Arts and Sciences. “We’re harnessing the passion and commitment from both faculty and alumni to institute these initiatives and expand our efforts to other foundational courses throughout the College.”

Physics and biology were chosen as the pilot departments for ALI, each converting large course sequences to the new model. Because biology encompasses multiple departments, and the physics courses are part of a sequence required for engineering students, the pilot project will reach almost 3,000 students.

Jed Sparks, professor of ecology and evolutionary biology and ALI project lead for biology, emphasizes that the initiative is “not fixing bad or broken classes but ones that are well received — making something that works well work even better.”

ALI uses a “flipped classroom” approach, where knowledge transfer happens before class, through assigned reading material or videos. Class time is then used for “deliberate practice,” applying the new knowledge via problem-solving and reasoning practice to give students experience making and testing predictions and solving problems. Studies have shown that the deliberate practice model is the quickest path to expert-level mastery of a given skill set.

The ALI model benefits students of all levels. Those with more advanced understanding benefit from the deeper level at which the courses operate, while mid-range students have far more opportunity to develop expert-level skills during the semester, acquiring more skills and greater exposure to more material. Students whose preparation is the weakest benefit from the improved opportunities to engage the course material and develop and practice skills; achievement gaps can thus be closed more rapidly than was possible in the past.

“ALI is a perfect example of Cornell’s dedication to taking our long history of excellent education into the future,” says Tomás Arias, associate professor and ALI project lead for physics. “We’re helping our students improve their level of retention and be better prepared to compete in the global intellectual marketplace.”

The College of Arts and Sciences is partnering with the Center for Teaching Excellence (CTE) in ALI. “Research and our own experience tell us that these interactive techniques contribute to enhanced learning,” says Theresa Pettit, CTE director. “What is particularly exciting about ALI is that it is a coordinated effort to build engaged learning into the curriculum at the departmental level with the potential to expand across campus.”

Developing the curricula for the pilot classes requires re-examining lecture objectives and what material should be covered, says Sparks. “In order for the active learning model to be successful, the teacher must have very clearly in mind what the teaching objectives for the class are. It requires them to teach in a more deliberate and intentional way. It’s transformative.”

The new learning model expects more of students as well as teachers, says Arias. “They must have the discipline to do their preparation before class, but by doing so, we can take them further and deeper than we could before.”

While some students in the pilot classes had had experience with active learning techniques in high school, for others the ALI model was unlike anything they’d experienced before. The biology class evaluations show an overwhelmingly positive response. One student noted that the ALI approach boosted his confidence in the class; others singled out the peer learning opportunities for praise.

To read the full article, click here.

 

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