Physics & Astronomy News
Dr. Chatzopoulos talks about the Eclipse & Einstein's Theory of General Relativity
WAFB Chanel 9 interviewed Dr. Chatopoulos's for Solar Eclipse event in LSU.
The Sun, The Moon and a Balloon - LSU Students to Launch Weather Balloon To Record the 2017 Eclipse
On August 21, a solar eclipse will pass across the United States, first darkening Oregon and creating a path of totality all the way to South Carolina over the course of a few hours. Everyone along this path will experience a few minutes of complete darkness along with the spectacular features of a total solar eclipse. The rest of the nation will experience a partial solar eclipse. Those not along the path of totality may feel like they are missing out, but NASA’s Eclipse Balloon Project has a solution for that!
Solar Eclipse at the Start
August 21, 12-2pm lsu parade ground rain location: union
Summer 2017 Graduates
On Friday, August 4, LSU Physics & Astronomy welcomed 4 new PhD, 3 MS and 4 BS graduates who conferred their degrees at the Marvavich Assembly Center.
Scientists Discover New Magnet with Nearly Massless Charge Carriers
Advances in modern electronics has demanded the requisite hardware, transistors, to be smaller in each new iteration. Recent progress in nanotechnology has reduced the size of silicon transistors down to the order of 10 nanometers. However, for such small transistors, other physical effects set in, which limit their functionality. For example, the power consumption and heat production in these devices is creating significant problems for device design. Therefore, novel quantum materials and device concepts are required to develop a new generation of energy-saving information technology. The recent discoveries of topological materials — a new class of relativistic quantum materials — hold great promise for use in energy saving electronics. Researchers in the Louisiana Consortium for Neutron Scattering, or LaCNS, led by LSU Department of Physics & Astronomy Chair and Professor John F. DiTusa and Tulane University Professor Zhiqiang Mao, with collaborators at Oak Ridge National Lab, the National High Magnetic Field Laboratory, Florida State University, and the University of New Orleans, recently reported the first observation of this topological behavior in a magnet, Sr1-yMn1-zSb2 (y, z < 0.1). These results were published this week in Nature Materials (doi:10.1038/nmat4953).
Total Solar Eclipse Teachers' Toolkit Tips and tools for teaching and viewing the eclipse safely on Aug. 21
BATON ROUGE - On August 21, 2017, a solar eclipse will be visible across North America, passing through the U.S. from Oregon to South Carolina. A solar eclipse occurs when the Moon's shadow passes over the Earth's surface, temporarily blocking the view of the Sun from the Earth. The last time a total solar eclipse occurred in the continental U.S. was 1979. This year, on Aug. 21, the eclipse will pass over the country again, with an 80% partial eclipse visible in Louisiana. With a grant from the Louisiana Space Grant Consortium (LaSPACE), Dr. Dana Browne, Professor and Associate Chair of the LSU Department of Physics & Astronomy, led a small team of K-12 teachers to develop a website toolkit for educators to teach students about the solar eclipse.
"Misconceptions associated with the Origin of Charge Density Waves," Xuetao Zhu, Jiandong Guo, Jiandi Zhang, and E. W. Plummer, Advances in Physics: X, 2, 622 (2017).
Charge density wave (CDW) is an important concept in condensed matter physics, germane to a number of physical phenomena. But the origin of CDW is still under debate, partly because the origin and properties of CDW are highly material-dependent. The concept of a CDW has been applied to many materials without a clear definition of the fundamental nature of CDW. As a result, misconceptions about CDW can be seen in literature. In this review, we will try to describe and explain the possible existing misconceptions associated with the origin of CDWs.
Louisiana Space Grant Teams Up with NASA to Livestream Total Solar Eclipse
A team of students and faculty from the Louisiana Space Grant Consortium, LaSPACE, led by LSU and including Delgado Community College, or DCC; Louisiana Tech University, or LaTech; and McNeese State University, or MSU, will launch two high-altitude balloons on Aug. 21 as part of a NASA-sponsored project to live-stream aerial video footage of the “Great American Eclipse.”
“Non-Trivial Berry Phase in Magnetic BaMnSb2 Semimetal,” Silu Huang, Jisun Kim, W. A. Shelton, E. W. Plummer, Rongying Jin, Proceedings National Academy of Sciences, 114, 6256 (2017).
Among topological materials, experimental study of topological semimetals that host Dirac/Weyl fermions has just begun, even though these topological concepts were proposed nearly a century ago by Dirac and Weyl. Our work shows magnetic-semimetal BaMnSb2 exhibits nearly zero-mass fermions with high mobility and a non-trivial Berry phase. What is unique is the magnetic ordering, indicating the system is Weyl type due to time-reversal symmetry breaking. Theory shows that the spin order is very fragile, so it is expected that the application of magnetic field or uniaxial pressure could drive the material to be a type-II Weyl semimetal.
“Interface-induced multiferroism by design in complex oxide superlattices,” H.W. Guo, Z. Wang, S. Dong, S. Ghosh, M. Saghayezhian, L. Chen, Y. Weng, A. Herklotz, T.Z. Ward, R. Jin, S.T. Pantelides, Y. Zhu, J. Zhang & E.W. Plummer Proceedings of the Nation
Developments in synthesis and characterization of artificially structured materials has greatly advanced the possibility to explore new states of matter in material science. Recent discoveries show that new quantum states can be achieved at hetero-interfaces with various electromagnetic and mechanical boundary conditions. It remains an open question on how to design ultrathin layers with properties inaccessible in bulk phases, which is amenable to technological applications. In this work, we grow heterostructures with extremely high quality interfaces, characterized by state-of-the-art atomically resolved electron microscopy and spectroscopy. This combination allows us to identify an interface-induced structure that stabilizes ferromagnetism. Coupled with theory, we provide conceptually useful recipe to design low-dimensional materials with novel functionalities, in line with the loop of “make, measure, model”.
MEDIA ADVISORY: Stephen Hawking Invites Gabriela González to Speak at 75th Birthday Symposium
Professor Gabriela González is one of four high-profile speakers invited to share the stage with Stephen Hawking for his 75th birthday public symposium on Sunday July 2, from 7 a.m. to noon (CST). The public event at Cambridge University will be livestreamed by Discover Science on Facebook and YouTube.
“Surface Sum Frequency Generation Spectroscopy from non-centrosymmetric Crystal GaAs (001),” Zhenyu Zhang, Jisun Kim, Rami Khoury, Louis H. Haber, and E. W. Plummer, Surface Science, 664, 21 (2017).
Femtosecond broadband sum frequency generation (SFG) spectroscopy is applied to surface studies of the archetypical non-centrosymmetric semiconductor GaAs (001). Azimuthal angular dependence studies in reflection geometry under eight possible polarization configurations reveal strong surface-bulk interference owing to heterodyne amplification. The crystal symmetry and the surface quadrupole contributions need to be considered to properly interpret the resulting nonlinear spectroscopic signals. In addition, over bandgap excitation by one of the incident beams brings the semiconductor surface to a transient excited state, enabling enhanced sensitivity of broadband SFG to probe the surface electronic properties of non-centrosymmetric semiconductors. These findings suggest that this technique can be generally applied to surface studies of other non-centrosymmetric crystals.
“Mn-induced magnetic symmetry breaking and its correlation with the metal-insulator transition in bilayered Sr3(Ru1-xMnx)2O7,’ Qiang Zhang, Zhenyu Diao, Rongying Jin, Jiandi Zhang, and Ward Plummer, etc.
Bilayered Sr3Ru2O7 is an unusual metamagnetic metal with inherently antiferromagnetic (AFM) and ferromagnetic (FM) fluctuations. Partial substitution of Ru by Mn results in the establishment of metal-insulator transition (MIT) at TMIT and AFM ordering at TM in Sr3(Ru1-xMnx)2O7. Using elastic neutron scattering we determined the effect of Mn doping on the magnetic structure and in-plane magnetic correlation lengths in Sr3(Ru1-xMnx)2O7 (x = 0.06 and 0.12). With increasing Mn doping (x) from 0.06 to 0.12 or decreasing temperatures for x=0.12, an evolution from an in-plane short-range to long-range double-stripe AFM ground state occurs. For both compounds, the onset of magnetic correlation with an anisotropic behavior coincides with the sharp rise of the electrical resistivity and the specific heat. Since it does not induce measurable lattice distortion, the double-stripe magnetic order with anisotropic spin texture breaks the symmetry from C4v crystal lattice to C2v magnetic sublattice. These observations shed new light on an age-old question of Slater versus Mott-type MIT.
“Manipulating the Polar mismatch at LaNiO3/SrTiO3 (111) Interface,” M. Saghayezhian, Zhen Wang, Hangwen Guo, E.W. Plummer, Jiandi Zhang, Phys. Rev. B (2017).
Heteroepitaxial growth of transition-metal oxide films on the open (111) surface of SrTiO3 results in significant restructuring due to the polar mismatch. Monitoring the structural and composition on an atomic scale of LaNiO3/SrTiO3 (111) interface as a function of processing conditions has enabled the avoidance of the expected polar catastrophe. Using atomically resolved transmission electron microscopy and spectroscopy as well as Low energy electron diffraction, the structure of the thin film, from interface to the surface, has been studied. In this paper, we show that the proper processing can lead to a structure that is ordered, coherent with the substrate without intermediate structural phase. Angle-resolved X-ray photoemission spectroscopy shows that the oxygen content of thin films increases with the film thickness, indicating that the polar mismatch is avoided by the presence of oxygen vacancies.
“Delicate competing electronic states in ultrathin manganite films,” Zhaoliang Liao, Rongying Jin, E. W. Plummer, Jiandi Zhang, Phys. Rev. B, 95, 085130 (2017).
The coupling between the electrical transport properties of L a 2 / 3 S r 1 / 3 Mn O 3 (LSMO) thin films and structural phase transitions of SrTi O 3 (STO) substrates at T s = 105 K has been investigated. We found that the electrical resistivity of LSMO films exhibit a “cusp” at T s , which is greatly amplified by tuning films to the verge of metallic and insulating phases, i.e., to the boundary of two delicate competing electronic states. Our results demonstrate that small amounts of strain can tip the subtle balance of competing interactions and tune the electronic properties in correlated electron materials.
Alum Edward Montiel Soars to New Heights to Explore our Universe
LSU alum Edward Montiel graduated with his PhD from LSU Department of Physics & Astronomy in August, 2016 and is currently a postdoctoral researcher at University of California, Davis. He helps process data for guest investigators using the world's largest flying telescope SOFIA and deliver science-ready data to them for their analyses.
Joyoni Dey awarded innovation (LIFT2) grant
Technology that will improve X-rays and medical imaging is one of the 13 innovations the LSU Board of Supervisors recently selected to support through its innovation and technology transfer grant. LSU Department of Physics & Astronomy Assistant Professor Joyoni Dey, along with a Ph.D. student and colleagues at the LSU Center for Advanced Microstructures and Devices, have established the technology to create more detailed X-rays that will aid doctors analyzing lung and bone joint scans. This technology will also provide higher contrast images for mammograms.
Jonathan Dowling on the implication of quantum physics
The Newsweek interviewed Jonathan Dowling on the implication of quantum physics:"Cybersecurity Attacks Are a Global Threat. Chinese Scientists Have the Answer: Quantum Mechanics"
Dr. Adams recent paper "Research Team Studies SC in Ultrathin Al Films" on the Zeeman PD of epitaxial Al films was featured in Superconducting Week.
Researchers with LSU, UT Asutin, and Forschungszentrum Jülich have completed a study of the Zeeman-mediated superconducting phase diagram in ultrathin crystalline aluminum films.
Baton Rouge imaging collaboration strives to combat obesity and improve cancer treatment
In a state with the highest obesity rate in the nation - 36 percent - researchers in Louisiana are pushing to find new and better ways to combat this chronic disease. The battle against such a prevalent health problem is no small task. It requires scientists to uncover countless mysteries which still surround how and why our bodies work the way they do before they can begin to develop targeted therapies aimed at preventing and treating obesity.