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  • richardmitnick 4:38 pm on July 7, 2021 Permalink | Reply
    Tags: "Quantum Laser Turns Energy Loss into Gain​", , KAIST-Korea Advanced Institute of Science and Technology [한국과학기술원 카이스트] (KR), , Parity-time reversal symmetry,   

    From KAIST-Korea Advanced Institute of Science and Technology [한국과학기술원 카이스트] (KR): “Quantum Laser Turns Energy Loss into Gain​” 

    From KAIST-Korea Advanced Institute of Science and Technology [한국과학기술원 카이스트] (KR)

    2021-07-07

    A new laser that generates quantum particles can recycle lost energy for highly efficient, low threshold laser applications.

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    Exciton-polaritonic PT symmetry: Direct coupling between upward- and downward-polariton modes in a six-fold symmetric microcavity with loss manipulation leads to PT-symmetry breaking with low-threshold phase transition.

    Scientists at KAIST have fabricated a laser system that generates highly interactive quantum particles at room temperature. Their findings, published in the journal Nature Photonics, could lead to a single microcavity laser system that requires lower threshold energy as its energy loss increases.

    The system, developed by KAIST physicist Yong-Hoon Cho and colleagues, involves shining light through a single hexagonal-shaped microcavity treated with a loss-modulated silicon nitride substrate. The system design leads to the generation of a polariton laser at room temperature, which is exciting because this usually requires cryogenic temperatures.

    The researchers found another unique and counter-intuitive feature of this design. Normally, energy is lost during laser operation. But in this system, as energy loss increased, the amount of energy needed to induce lasing decreased. Exploiting this phenomenon could lead to the development of high efficiency, low threshold lasers for future quantum optical devices.

    “This system applies a concept of quantum physics known as parity-time reversal symmetry,” explains Professor Cho. “This is an important platform that allows energy loss to be used as gain. It can be used to reduce laser threshold energy for classical optical devices and sensors, as well as quantum devices and controlling the direction of light.”

    The key is the design and materials. The hexagonal microcavity divides light particles into two different modes: one that passes through the upward-facing triangle of the hexagon and another that passes through its downward-facing triangle. Both modes of light particles have the same energy and path but don’t interact with each other.

    However, the light particles do interact with other particles called excitons, provided by the hexagonal microcavity, which is made of semiconductors. This interaction leads to the generation of new quantum particles called polaritons that then interact with each other to generate the polariton laser. By controlling the degree of loss between the microcavity and the semiconductor substrate, an intriguing phenomenon arises, with the threshold energy becoming smaller as energy loss increases. This research was supported by the Samsung Science and Technology Foundation and Korea’s National Research Foundation.

    See the full article here.

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    <a href="http:// KAIST-Korea Advanced Institute of Science and Technology [한국과학기술원 카이스트] (KR) is the first and top science and technology university in Korea. KAIST has been the gateway to advanced science and technology, innovation, and entrepreneurship, and our graduates have been key players behind Korea’ innovations. KAIST will continue to pursue advances in science and technology as well as the economic development of Korea and beyond.

    KAIST educates, researches, and takes the lead in innovations to serve the happiness and prosperity of humanity. KAIST fosters talents who exhibit creativity, embrace challenges, and possess caring minds in creating knowledge and translating it into transformative innovation.

     
  • richardmitnick 10:37 am on July 6, 2021 Permalink | Reply
    Tags: "Defining the Hund Physics Landscape of Two-Orbital Systems", , , KAIST-Korea Advanced Institute of Science and Technology [한국과학기술원 카이스트] (KR),   

    From KAIST-Korea Advanced Institute of Science and Technology [한국과학기술원 카이스트] (KR): “Defining the Hund Physics Landscape of Two-Orbital Systems” 

    From KAIST-Korea Advanced Institute of Science and Technology [한국과학기술원 카이스트] (KR)

    Researchers identify exotic metals in unexpected quantum systems.

    1
    Figure: Phase diagram of two-orbital systems. Various metals emerge depending on the values of electron interactions denoted by U (x-axis) and Hund’s coupling J/U (y-axis).

    Electrons are ubiquitous among atoms, subatomic tokens of energy that can independently change how a system behaves—but they also can change each other. An international research collaboration found that collectively measuring electrons revealed unique and unanticipated findings. The researchers published their results on May 17 in Physical Review Letters.

    “It is not feasible to obtain the solution just by tracing the behavior of each individual electron,” said paper author Myung Joon Han, professor of physics at KAIST. “Instead, one should describe or track all the entangled electrons at once. This requires a clever way of treating this entanglement.”

    Professor Han and the researchers used a recently developed “many-particle” theory to account for the entangled nature of electrons in solids, which approximates how electrons locally interact with one another to predict their global activity.

    Through this approach, the researchers examined systems with two orbitals — the space in which electrons can inhabit. They found that the electrons locked into parallel arrangements within atom sites in solids. This phenomenon, known as Hund’s coupling, results in a Hund’s metal. This metallic phase, which can give rise to such properties as superconductivity, was thought only to exist in three-orbital systems.

    “Our finding overturns a conventional viewpoint that at least three orbitals are needed for Hund’s metallicity to emerge,” Professor Han said, noting that two-orbital systems have not been a focus of attention for many physicists. “In addition to this finding of a Hund’s metal, we identified various metallic regimes that can naturally occur in generic, correlated electron materials.”

    The researchers found four different correlated metals. One stems from the proximity to a Mott insulator, a state of a solid material that should be conductive but actually prevents conduction due to how the electrons interact. The other three metals form as electrons align their magnetic moments — or phases of producing a magnetic field — at various distances from the Mott insulator. Beyond identifying the metal phases, the researchers also suggested classification criteria to define each metal phase in other systems.

    “This research will help scientists better characterize and understand the deeper nature of so-called ‘strongly correlated materials,’ in which the standard theory of solids breaks down due to the presence of strong Coulomb interactions between electrons,” Professor Han said, referring to the force with which the electrons attract or repel each other. These interactions are not typically present in solid materials but appear in materials with metallic phases.

    The revelation of metals in two-orbital systems and the ability to determine whole system electron behavior could lead to even more discoveries, according to Professor Han.

    “This will ultimately enable us to manipulate and control a variety of electron correlation phenomena,” Professor Han said.

    Co-authors include Siheon Ryee from KAIST and Sangkook Choi from the Condensed Matter Physics and Materials Science Department, DOE’s Brookhaven National Laboratory (US). Korea’s National Research Foundation and the U.S. Department of Energy’s (DOE) Office of Science, Basic Energy Sciences, supported this work.

    See the full article here.

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    <a href="http:// KAIST-Korea Advanced Institute of Science and Technology [한국과학기술원 카이스트] (KR) is the first and top science and technology university in Korea. KAIST has been the gateway to advanced science and technology, innovation, and entrepreneurship, and our graduates have been key players behind Korea’ innovations. KAIST will continue to pursue advances in science and technology as well as the economic development of Korea and beyond.

    KAIST educates, researches, and takes the lead in innovations to serve the happiness and prosperity of humanity. KAIST fosters talents who exhibit creativity, embrace challenges, and possess caring minds in creating knowledge and translating it into transformative innovation.

     
  • richardmitnick 11:34 am on April 5, 2021 Permalink | Reply
    Tags: "Streamlining the Process of Materials Discovery​", , KAIST-Korea Advanced Institute of Science and Technology [한국과학기술원 카이스트] (KR), M3I3: Materials and Molecular Modeling; Imaging; Informatics; and Integration.   

    From KAIST-Korea Advanced Institute of Science and Technology [한국과학기술원 카이스트] (KR): “Streamlining the Process of Materials Discovery​” 

    From KAIST-Korea Advanced Institute of Science and Technology [한국과학기술원 카이스트] (KR)

    2021-04-05

    The materials platform M3I3 reduces the time for materials discovery by reverse engineering future materials using multiscale/multimodal imaging and machine learning of the processing-structure-properties relationship.

    1
    Researchers of M3I3 Initiative at the Department of Materials Science and Enginering: Professor EunAe Cho, Professor Hye Ryung Byon, Professor Seungbum Hong, and Professor Jong Min Yuk.

    Developing new materials and novel processes has continued to change the world. The M3I3 Initiative at KAIST has led to new insights into advancing materials development by implementing breakthroughs in materials imaging that have created a paradigm shift in the discovery of materials. The Initiative features the multiscale modeling and imaging of structure and property relationships and materials hierarchies combined with the latest material-processing data.

    The research team led by Professor Seungbum Hong analyzed the materials research projects reported by leading global institutes and research groups, and derived a quantitative model using machine learning with a scientific interpretation. This process embodies the research goal of the M3I3: Materials and Molecular Modeling; Imaging; Informatics; and Integration.

    The researchers discussed the role of multiscale materials and molecular imaging combined with machine learning and also presented a future outlook for developments and the major challenges of M3I3. By building this model, the research team envisions creating desired sets of properties for materials and obtaining the optimum processing recipes to synthesize them.

    “The development of various microscopy and diffraction tools with the ability to map the structure, property, and performance of materials at multiscale levels and in real time enabled us to think that materials imaging could radically accelerate materials discovery and development,” says Professor Hong.

    “We plan to build an M3I3 repository of searchable structural and property maps using FAIR (Findable, Accessible, Interoperable, and Reusable) principles to standardize best practices as well as streamline the training of early career researchers.”

    2
    Figure 1. Schematic diagram of the M3I3 Flagship Project. This project aims to achieve the seamless integration of the multiscale “structure–property” and “processing–property” relationships via materials modeling, imaging, and machine learning. With the capability of artificial intelligence (AI)-guided automatic synthesis, M3I3 will provide expedited development of new materials in the near future.

    One of the examples that shows the power of structure-property imaging at the nanoscale is the development of future materials for emerging nonvolatile memory devices. Specifically, the research team focused on microscopy using photons, electrons, and physical probes on the multiscale structural hierarchy, as well as structure-property relationships to enhance the performance of memory devices.

    “M3I3 is an algorithm for performing the reverse engineering of future materials. Reverse engineering starts by analyzing the structure and composition of cutting-edge materials or products. Once the research team determines the performance of our targeted future materials, we need to know the candidate structures and compositions for producing the future materials.”

    The research team has built a data-driven experimental design based on traditional NCM (nickel, cobalt, and manganese) cathode materials. With this, the research team expanded their future direction for achieving even higher discharge capacity, which can be realized via Li-rich cathodes.

    However, one of the major challenges was the limitation of available data that describes the Li-rich cathode properties. To mitigate this problem, the researchers proposed two solutions: First, they should build a machine-learning-guided data generator for data augmentation. Second, they would use a machine-learning method based on ‘transfer learning.’ Since the NCM cathode database shares a common feature with a Li-rich cathode, one could consider repurposing the NCM trained model for assisting the Li-rich prediction. With the pretrained model and transfer learning, the team expects to achieve outstanding predictions for Li-rich cathodes even with the small data set.

    With advances in experimental imaging and the availability of well-resolved information and big data, along with significant advances in high-performance computing and a worldwide thrust toward a general, collaborative, integrative, and on-demand research platform, there is a clear confluence in the required capabilities of advancing the M3I3 Initiative.

    Professor Hong said, “Once we succeed in using the inverse “property−structure−processing” solver to develop cathode, anode, electrolyte, and membrane materials for high energy density Li-ion batteries, we will expand our scope of materials to battery/fuel cells, aerospace, automobiles, food, medicine, and cosmetic materials.”

    The review was published in ACS Nano in March. This study was conducted through collaborations with Dr. Chi Hao Liow, Professor Jong Min Yuk, Professor Hye Ryung Byon, Professor Yongsoo Yang, Professor EunAe Cho, Professor Pyuck-Pa Choi, and Professor Hyuck Mo Lee at KAIST, Professor Joshua C. Agar at Lehigh University (US), Dr. Sergei V. Kalinin at DOE’s Oak Ridge National Laboratory (US), Professor Peter W. Voorhees at Northwestern University (US), and Professor Peter Littlewood at the University of Chicago (US).This work was supported by the KAIST Global Singularity Research Program for 2019 and 2020.

    See the full article here.

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    <a href="http://From KAIST-Korea Advanced Institute of Science and Technology [한국과학기술원 카이스트] (KR)>KAIST is the first and top science and technology university in Korea. KAIST has been the gateway to advanced science and technology, innovation, and entrepreneurship, and our graduates have been key players behind Korea’ innovations. KAIST will continue to pursue advances in science and technology as well as the economic development of Korea and beyond.

    KAIST educates, researches, and takes the lead in innovations to serve the happiness and prosperity of humanity. KAIST fosters talents who exhibit creativity, embrace challenges, and possess caring minds in creating knowledge and translating it into transformative innovation.

     
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