Tagged: Columbia University (US) Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 3:34 pm on July 23, 2021 Permalink | Reply
    Tags: , , , , Columbia University (US), "Physicists Show That a Quantum Particle Made of Light and Matter Can Be Dragged by a Current of Electrons", A quasiparticle made of waves of photons and electrons—a plasmon polariton—has a similar ability to change speeds when immersed in an electrical current flowing through a sheet of graphene., The polaritons appear to more easily shift gears in one direction—to a slightly slower speed—when traveling against the flow of electrons., The finding is a big deal for "plasmonics"., Polariton waves are minuscule; dozens can squeeze into the wavelength of one photon., Polaritons are compact but still quantum which means they can be manipulated on ultra-fast time scales., As soon as you can control the speed and direction of polaritons you can transmit information in nanoscale circuits on ultrafast timescales.   

    From Columbia University (US) : “Physicists Show That a Quantum Particle Made of Light and Matter Can Be Dragged by a Current of Electrons” 

    Columbia U bloc

    From Columbia University (US)

    July 21, 2021
    Kim Martineau

    A pair of studies in Nature show that a quasiparticle, known as a plasmon polariton, can be pulled with and against a flow of electrons, a finding that could lead to more efficient ways of manipulating light at the nanoscale.

    1
    Columbia University graduate students Lin Xiong (left) and Yinan Dong image polaritons using a cryogenic microscope. Credit: Yinan Dong.

    Light was thought to move at a fixed rate until 1851, when a French physicist—the first to accurately clock the speed of light—showed it could also be slowed or accelerated simply by shining a light beam with or against the flow of moving water. Decades later, Einstein seized on Hippolyte Fizeau’s landmark water-pipe experiments in developing his theory of relativity.

    Now, new research in Nature shows that a quasiparticle made of waves of photons and electrons—a plasmon polariton—has a similar ability to change speeds when immersed in an electrical current flowing through a sheet of graphene. But there’s a hitch: the polaritons appear to more easily shift gears in one direction—to a slightly slower speed—when traveling against the flow of electrons.

    The finding is a big deal for plasmonics, a field with a rock-star name dedicated to finding new and efficient ways of controlling light down at the nearly invisible scale of individual atoms—for optical computing, nanolasers, and other applications, including imprinting patterns into semiconductors. Polaritons have two perks. Their relatively slow speed compared to photons makes them a good proxy for manipulating light. Polariton waves are also minuscule; dozens can squeeze into the wavelength of one photon.

    Dmitri Basov, a physics professor at Columbia, has devoted most of his lab to studying their behavior. “Polaritons possess the best virtues of electrons and photons,” he said. “They’re compact but still quantum which means they can be manipulated on ultra-fast time scales.”

    2
    In this illustration, a set of polariton waves (at left), interact with drifting electrons in a sheet of graphene. The warped fabric of space-time (upper left) represents the related concept of relativity. Credit: Yinan Dong, Denis Bandurin, and Ella Maru Studio.

    In the recent Nature study, Basov and his colleagues recreated Fizeau’s experiments on a speck of graphene made up of a single layer of carbon atoms. Hooking up the graphene to a battery, they created an electrical current reminiscent of Fizeau’s water streaming through a pipe. But instead of shining light on the moving water and measuring its speed in both directions, as Fizeau did, they generated an electromagnetic wave with a compressed wavelength—a polariton—by focusing infrared light on a gold nub in the graphene. The activated stream of polaritons look like light but are physically more compact due to their short wavelengths.

    The researchers clocked the polaritons’ speed in both directions. When they traveled with the flow of the electrical current, they maintained their original speed. But when launched against the current, they slowed by a few percentage points.

    An Unexpected Result

    “We were surprised when we saw it,” said study co-author Denis Bandurin, a physics researcher at Massachusetts Institute of Technology (US). “First, the device was still alive, despite the heavy current we passed through it—it hadn’t blown up. Then we noticed the one-way effect, which was different from Fizeau’s original experiments.”

    The researchers repeated the experiments over and over, led by the study’s first-author, Yinan Dong, a Columbia graduate student. Finally, it dawned on them. “Graphene is a material that turns electrons into relativistic particles,” Dong said. “We needed to account for their spectrum.”

    A group at DOE’s Lawrence Berkeley National Laboratory (US) found a similar result, published in the same issue of Nature. Beyond reproducing the Fizeau effect in graphene, both studies have practical applications. Most natural systems are symmetric, but here, researchers found an intriguing exception. Basov said he hopes to slow down, and ultimately, cut off the flow of polaritons in one direction. It’s not an easy task, but it could hold big rewards.

    “Engineering a system with a one-way flow of light is very difficult to achieve,” said Milan Delor, a physical chemist working on light-matter interactions at Columbia who was not involved in the research. “As soon as you can control the speed and direction of polaritons you can transmit information in nanoscale circuits on ultrafast timescales. It’s one of the ingredients currently missing in photon-based circuits.”

    Optical isolators are currently used to limit the bounce-back of light in everything from lasers to the fiber optic cables in broadband. But they’re bulky and incompatible with modern nanocircuits, making polaritons, with their potential to be shut off in one direction, so appealing.

    Plasmonics researchers are also excited about the detailed images to come out of the experiments. They show that polaritons can serve as nanoscale probes, they said, triggering and recording electron-electron interactions in a system. This information provides clues about how graphene and other quantum materials will behave in the real world.

    “The images are effectively a read-out of the material properties of graphene,” Delor said.

    The Enablers of “Nanoptics”

    “I like to call polaritons the enablers of nanoptics,” says James Schuck, a mechanical engineer and plasmonics researcher at Columbia Engineering who was not involved in the work. “They’re useful for probing all sorts of materials at the nanoscale.”

    Most of the experiments were done during the pandemic; the researchers wore masks and gloves and disinfected the lab after each visit. “There was no slow-down for quantum physics,” says Basov, with a laugh, evoking Fizeau.

    The French physicist’s name was later inscribed on the Eiffel Tower; not for the effect that bears his name, but for precisely measuring the speed of light. Fizeau’s work was popularized in a lecture series at Columbia in 1906, as Basov likes to remind students. Fizeau was also an early photographic experimenter. Some of his ghostly daguerreotype views of the rooftops of Paris are held by The Metropolitan Museum of Art, not far from the Columbia campus.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Columbia U Campus
    Columbia University (US) was founded in 1754 as King’s College by royal charter of King George II of England. It is the oldest institution of higher learning in the state of New York and the fifth oldest in the United States.

    University Mission Statement

    Columbia University is one of the world’s most important centers of research and at the same time a distinctive and distinguished learning environment for undergraduates and graduate students in many scholarly and professional fields. The University recognizes the importance of its location in New York City and seeks to link its research and teaching to the vast resources of a great metropolis. It seeks to attract a diverse and international faculty and student body, to support research and teaching on global issues, and to create academic relationships with many countries and regions. It expects all areas of the University to advance knowledge and learning at the highest level and to convey the products of its efforts to the world.

    Columbia University is a private Ivy League research university in New York City. Established in 1754 on the grounds of Trinity Church in Manhattan Columbia is the oldest institution of higher education in New York and the fifth-oldest institution of higher learning in the United States. It is one of nine colonial colleges founded prior to the Declaration of Independence, seven of which belong to the Ivy League. Columbia is ranked among the top universities in the world by major education publications.

    Columbia was established as King’s College by royal charter from King George II of Great Britain in reaction to the founding of Princeton College. It was renamed Columbia College in 1784 following the American Revolution, and in 1787 was placed under a private board of trustees headed by former students Alexander Hamilton and John Jay. In 1896, the campus was moved to its current location in Morningside Heights and renamed Columbia University.

    Columbia scientists and scholars have played an important role in scientific breakthroughs including brain-computer interface; the laser and maser; nuclear magnetic resonance; the first nuclear pile; the first nuclear fission reaction in the Americas; the first evidence for plate tectonics and continental drift; and much of the initial research and planning for the Manhattan Project during World War II. Columbia is organized into twenty schools, including four undergraduate schools and 15 graduate schools. The university’s research efforts include the Lamont–Doherty Earth Observatory, the Goddard Institute for Space Studies, and accelerator laboratories with major technology firms such as IBM. Columbia is a founding member of the Association of American Universities and was the first school in the United States to grant the M.D. degree. With over 14 million volumes, Columbia University Library is the third largest private research library in the United States.

    The university’s endowment stands at $11.26 billion in 2020, among the largest of any academic institution. As of October 2020, Columbia’s alumni, faculty, and staff have included: five Founding Fathers of the United States—among them a co-author of the United States Constitution and a co-author of the Declaration of Independence; three U.S. presidents; 29 foreign heads of state; ten justices of the United States Supreme Court, one of whom currently serves; 96 Nobel laureates; five Fields Medalists; 122 National Academy of Sciences members; 53 living billionaires; eleven Olympic medalists; 33 Academy Award winners; and 125 Pulitzer Prize recipients.

     
  • richardmitnick 9:17 pm on June 16, 2021 Permalink | Reply
    Tags: "Kepler 52 and Kepler 968-Young exoplanet siblings", , , , Columbia University (US), , ,   

    From Columbia University (US) via COSMOS (AU) : “Kepler 52 and Kepler 968-Young exoplanet siblings” 

    Columbia U bloc

    From Columbia University (US)

    via

    Cosmos Magazine bloc

    COSMOS (AU)

    16 June 2021
    Richard A. Lovett

    The exoplanets Kepler 52 and Kepler 968 are really part of a bigger system.

    Two exoplanet systems – Kepler 52 and Kepler 968 – that have been drifting across the galaxy for hundreds of millions of years have proven to be parts of a 400-member star cluster.

    The two systems were discovered several years ago by NASA’s Kepler space telescope, which spotted them when they passed between us and their stars, causing their stars’ light to dim briefly.

    At the time, they were thought to be unrelated. But in 2019, astronomers using data from the European Space Agency’s Gaia space telescope realised they were part of a far-flung cluster called Theia 520, which spans a 20-degree swath across the northern sky.

    This isn’t a cluster you could see on your own. “It’s really diffuse and sprawling,” says Jason Curtis of Columbia University, speaking last week at a virtual meeting of the American Astronomical Society (US).

    Science paper

    It was only the precision of the Gaia space telescope that allowed it to be spotted at all, because Gaia’s hyper-precise star-tracking data revealed all the stars in it to be moving in a single, coherent group. This indicated that they had come from the same birth cluster, now dispersing.

    The next step, Curtis says, was to figure out how old the two planetary systems were. Prior estimates of the ages of their stars had been inconclusive, serving up answers that spanned pretty much the entire age of the universe.

    But once he knew they were both members of a cluster, Curtis says, it was possible to use a different method to determine the age of the cluster, rather than the individual stars.

    To do that, he and a team of high school students used data from Kepler, Gaia, and a 48-inch telescope on Mount Palomar in Southern California to calculate the rotation rates of 130 of Theia 520’s stars, graphing them against the stars’ masses.

    All of this was done with publicly available date, easily available online.

    “This underscores the importance of all-sky surveys and public archives,” says Marcel Agüeros, an astronomer at Columbia University and a co-author of the study.

    The results proved that the Kepler 52 and Kepler 968 stars aren’t all that ancient. Instead, Curtis says, they appear to be about 350 million years old.

    That’s because stars in a cluster are born spinning at a fairly wide range of rates, ranging from a few hours to a few days or tens of days. But as they age, they slow down, with faster-rotating stars slowing more quickly than slower-rotating ones, and bigger ones responding differently from smaller ones.

    By graphing the distribution of spin rates against mass, Curtis says, it’s possible to estimate the age of a cluster. “At any age there’s a unique signature,” he says.

    Doing this for clusters with known exoplanet systems is important, he adds, because it helps astronomers understand how planetary systems evolve over time.

    “Planets in clusters provide us with a snapshot in time,” says Elisabeth Newton, an astronomer at Dartmouth College who was not involved in the study. “When we know exactly how old planets are, we can use them to piece together the story of how planets and planetary systems evolve. Knowing that Kepler 52 and 968 are only a few hundred million years old is especially valuable because we haven’t yet found many planets that young.”

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Columbia U Campus
    Columbia University (US) was founded in 1754 as King’s College by royal charter of King George II of England. It is the oldest institution of higher learning in the state of New York and the fifth oldest in the United States.

    University Mission Statement

    Columbia University is one of the world’s most important centers of research and at the same time a distinctive and distinguished learning environment for undergraduates and graduate students in many scholarly and professional fields. The University recognizes the importance of its location in New York City and seeks to link its research and teaching to the vast resources of a great metropolis. It seeks to attract a diverse and international faculty and student body, to support research and teaching on global issues, and to create academic relationships with many countries and regions. It expects all areas of the University to advance knowledge and learning at the highest level and to convey the products of its efforts to the world.

    Columbia University is a private Ivy League research university in New York City. Established in 1754 on the grounds of Trinity Church in Manhattan Columbia is the oldest institution of higher education in New York and the fifth-oldest institution of higher learning in the United States. It is one of nine colonial colleges founded prior to the Declaration of Independence, seven of which belong to the Ivy League. Columbia is ranked among the top universities in the world by major education publications.

    Columbia was established as King’s College by royal charter from King George II of Great Britain in reaction to the founding of Princeton College. It was renamed Columbia College in 1784 following the American Revolution, and in 1787 was placed under a private board of trustees headed by former students Alexander Hamilton and John Jay. In 1896, the campus was moved to its current location in Morningside Heights and renamed Columbia University.

    Columbia scientists and scholars have played an important role in scientific breakthroughs including brain-computer interface; the laser and maser; nuclear magnetic resonance; the first nuclear pile; the first nuclear fission reaction in the Americas; the first evidence for plate tectonics and continental drift; and much of the initial research and planning for the Manhattan Project during World War II. Columbia is organized into twenty schools, including four undergraduate schools and 15 graduate schools. The university’s research efforts include the Lamont–Doherty Earth Observatory, the Goddard Institute for Space Studies, and accelerator laboratories with major technology firms such as IBM. Columbia is a founding member of the Association of American Universities and was the first school in the United States to grant the M.D. degree. With over 14 million volumes, Columbia University Library is the third largest private research library in the United States.

    The university’s endowment stands at $11.26 billion in 2020, among the largest of any academic institution. As of October 2020, Columbia’s alumni, faculty, and staff have included: five Founding Fathers of the United States—among them a co-author of the United States Constitution and a co-author of the Declaration of Independence; three U.S. presidents; 29 foreign heads of state; ten justices of the United States Supreme Court, one of whom currently serves; 96 Nobel laureates; five Fields Medalists; 122 National Academy of Sciences members; 53 living billionaires; eleven Olympic medalists; 33 Academy Award winners; and 125 Pulitzer Prize recipients.

     
  • richardmitnick 10:21 am on May 15, 2021 Permalink | Reply
    Tags: "Gazing Into a Diamond's Flaws Has Revealed Hidden Clues About How Our Planet Formed", A diamond's structure appears to prevent helium from leaking out allowing the scientists to age these rocks using the rare isotope of helium-4., After a diamond captures something from that moment until millions of years later that material stays the same., , Columbia University (US), Dirty-looking gems are where tiny vaults of information lie stuffed with messages from Earth's inner depths., Extreme heat and crushing pressures from all the rock above can force carbon atoms into the neatly ordered structure of a diamond., , , Some cavities in the diamond's structure have captured fluids that once infiltrated the continental lithospheric mantle., The team identified three distinct periods of diamond formation in the subterranean rock masses that eventually squished together to form the mantle of Africa.   

    From Columbia University (US) via Science Alert (AU) : “Gazing Into a Diamond’s Flaws Has Revealed Hidden Clues About How Our Planet Formed” 

    Columbia U bloc

    From Columbia University (US)

    via

    ScienceAlert

    Science Alert (AU)

    15 MAY 2021
    TESSA KOUMOUNDOUROS

    1
    A diamond encapsulating miniscule bits of fluid from Earth’s depths. Credit: Yaakov Weiss/Columbia University.

    More than mere beautiful, coveted stones, diamonds hold another sort of wealth: fragments of Earth’s deep history.

    From flaws within the mineral’s near-perfect lattice, scientists have just worked out how to extract long-hidden records of our planet’s past.

    “We like the ones that no one else really wants,” said geochemist Yaakov Weiss from Columbia University, referring to the diamonds full of impurities that don’t look as clear and shiny as those desired for jewelry.

    These fibrous, dirty-looking gems are where tiny vaults of information lie stuffed with messages from Earth’s inner depths. The carbon structure of a perfect diamond doesn’t contain enough radioisotopes to help researchers date it, but the microinclusions found in its flaws can.

    These flaws can form tiny pockets that may encapsulate the chemicals from which the diamonds birthed.

    “After a diamond captures something, from that moment until millions of years later in my lab, that material stays the same,” explained Weiss back in 2015. “We can look at diamonds as time capsules, as messengers from a place we have no other way of seeing.”

    Sometimes these capsules contain other solids like strange forms of ice, usually inaccessible minerals from the bowels of our world, or even another diamond. These solid messages can be hard to interpret, as the inclusions may have formed at different times from the diamond capsule within which they now rest.

    Other cavities in the diamond’s structure have captured fluids that once infiltrated the continental lithospheric mantle. This layer of Earth is the uppermost part of the mantle (which lies between Earth’s crust and outer core), 150 to 200 kilometers (90 to 120 miles) beneath the surface, and it’s where diamonds are”born”.

    1
    Credit: Tumeggy/Science Photo Library/Getty Images.

    Here, extreme heat and crushing pressures from all the rock above can force carbon atoms into the neatly ordered structure of a diamond. In fact, the fluids that have seeped from above provide the carbon from which the diamonds are formed.

    Now a new technique has allowed the researchers to finally date those fluids within diamonds found in southern Africa.

    “This is the first time we can get reliable ages for these fluids,” said Weiss.

    3
    A diamond used in the study. Credit: Yaakov Weiss.

    A diamond’s structure appears to prevent helium from leaking out allowing Weiss and colleagues to age these rocks using the rare isotope of helium-4 – the ratios between radioactive atoms in the fluid inclusions and a product of their decay.

    Using this new method, the team identified three distinct periods of diamond formation in the subterranean rock masses that eventually squished together to form the mantle of Africa. The diamond-forming fluids changed across the ages, going from rich in carbonate to silicone and, finally, to saline.

    The first phase of diamond formation occurred during the Proterozoic, 2.6 billion to 750 million years ago, when these rocks collided into great mountain ranges. The researchers suspect these collisions allowed the carbonate-rich fluids to sink deep within Earth, but how exactly is still unknown.

    The next phase also coincided with a mountain-forming period, 540 to 300 million years ago during the Paleozoic, producing diamonds with silicone-rich inclusions. By this stage, the beginnings of the African-mantle-to-be were forming.

    Then, 130 to 85 million years ago during the Cretaceous, the fluid became saline rich – suggesting these diamonds were formed from what once was the ocean floor. This was dragged beneath the now-formed continental mass of Africa by subduction, where one continental plate is forced below another where they meet.

    The stones were all then carried closer to Earth’s surface through deep-reaching volcanic activity, such as the kimberlites eruptions 85 million years ago, where miners recently found them.

    “Southern Africa is one of the best-studied places in the world, but we’ve very rarely been able to see beyond the indirect indications of what happened there in the past,” said Columbia University (US) geochemist Cornelia Class, explaining these minuscule drops of fluid are a rare way to link events from deep within Earth with those on the surface.

    It’s worth noting that today, millions of workers rely on diamond mining as a source of income, but the conditions they work within can be brutal and may include human trafficking and child labor. The mines have also polluted soils and waterways relied upon by entire communities.

    The company from which the diamonds in this study were obtained, De Beers, one of the two largest diamond producers in the world, often doesn’t disclose which mines individual diamonds come from.

    So while diamonds can clearly reveal much about our geological history, their extraction from Earth can also come at an incredibly high price.

    This research was published in Nature Communications.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Columbia U Campus
    Columbia University (US) was founded in 1754 as King’s College by royal charter of King George II of England. It is the oldest institution of higher learning in the state of New York and the fifth oldest in the United States.

    University Mission Statement

    Columbia University is one of the world’s most important centers of research and at the same time a distinctive and distinguished learning environment for undergraduates and graduate students in many scholarly and professional fields. The University recognizes the importance of its location in New York City and seeks to link its research and teaching to the vast resources of a great metropolis. It seeks to attract a diverse and international faculty and student body, to support research and teaching on global issues, and to create academic relationships with many countries and regions. It expects all areas of the University to advance knowledge and learning at the highest level and to convey the products of its efforts to the world.

    Columbia University is a private Ivy League research university in New York City. Established in 1754 on the grounds of Trinity Church in Manhattan Columbia is the oldest institution of higher education in New York and the fifth-oldest institution of higher learning in the United States. It is one of nine colonial colleges founded prior to the Declaration of Independence, seven of which belong to the Ivy League. Columbia is ranked among the top universities in the world by major education publications.

    Columbia was established as King’s College by royal charter from King George II of Great Britain in reaction to the founding of Princeton College. It was renamed Columbia College in 1784 following the American Revolution, and in 1787 was placed under a private board of trustees headed by former students Alexander Hamilton and John Jay. In 1896, the campus was moved to its current location in Morningside Heights and renamed Columbia University.

    Columbia scientists and scholars have played an important role in scientific breakthroughs including brain-computer interface; the laser and maser; nuclear magnetic resonance; the first nuclear pile; the first nuclear fission reaction in the Americas; the first evidence for plate tectonics and continental drift; and much of the initial research and planning for the Manhattan Project during World War II. Columbia is organized into twenty schools, including four undergraduate schools and 15 graduate schools. The university’s research efforts include the Lamont–Doherty Earth Observatory, the Goddard Institute for Space Studies, and accelerator laboratories with major technology firms such as IBM. Columbia is a founding member of the Association of American Universities and was the first school in the United States to grant the M.D. degree. With over 14 million volumes, Columbia University Library is the third largest private research library in the United States.

    The university’s endowment stands at $11.26 billion in 2020, among the largest of any academic institution. As of October 2020, Columbia’s alumni, faculty, and staff have included: five Founding Fathers of the United States—among them a co-author of the United States Constitution and a co-author of the Declaration of Independence; three U.S. presidents; 29 foreign heads of state; ten justices of the United States Supreme Court, one of whom currently serves; 96 Nobel laureates; five Fields Medalists; 122 National Academy of Sciences members; 53 living billionaires; eleven Olympic medalists; 33 Academy Award winners; and 125 Pulitzer Prize recipients.

     
c
Compose new post
j
Next post/Next comment
k
Previous post/Previous comment
r
Reply
e
Edit
o
Show/Hide comments
t
Go to top
l
Go to login
h
Show/Hide help
shift + esc
Cancel
%d bloggers like this: