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Full-Text Articles in Physics

Correlations Between Short- And Long-Time Relaxation In Colloidal Supercooled Liquids And Glasses, Chandan K. Mishra, Xiaoguang Ma, Piotr Habdas, Kevin B. Aptowicz, A. G. Yodh Aug 2019

Correlations Between Short- And Long-Time Relaxation In Colloidal Supercooled Liquids And Glasses, Chandan K. Mishra, Xiaoguang Ma, Piotr Habdas, Kevin B. Aptowicz, A. G. Yodh

Physics

Spatiotemporal dynamics of short- and long-time structural relaxation are measured experimentally as a function of packing fraction, φ, in quasi-two-dimensional colloidal supercooled liquids and glasses. The relaxation times associated with long-time dynamic heterogeneity and short-time intracage motion are found to be strongly correlated and to grow by orders of magnitude with increasing φ toward dynamic arrest. We find that clusters of fast particles on the two timescales often overlap, and, interestingly, the distribution of minimum-spatial-separation between closest nonoverlapping clusters across the two timescales is revealed to be exponential with a decay length that increases with φ. In total, the experimental ...


Fatigue-Resistant High-Performance Elastocaloric Materials Via Additive Manufacturing, Huilong Hou, Emrah Simsek, Tao Ma, Nathan S. Johnson, Suxin Qian, Cheikh Cissé, Drew Stasak, Naila Al Hasan, Lin Zhou, Yunho Hwang, Reinhard Radermacher, Valery I. Levitas, Matthew J. Kramer, Mohsen Asle Zaeem, Aaron P. Stebner, Ryan T. Ott, Jun Cui, Ichiro Takeuchi Aug 2019

Fatigue-Resistant High-Performance Elastocaloric Materials Via Additive Manufacturing, Huilong Hou, Emrah Simsek, Tao Ma, Nathan S. Johnson, Suxin Qian, Cheikh Cissé, Drew Stasak, Naila Al Hasan, Lin Zhou, Yunho Hwang, Reinhard Radermacher, Valery I. Levitas, Matthew J. Kramer, Mohsen Asle Zaeem, Aaron P. Stebner, Ryan T. Ott, Jun Cui, Ichiro Takeuchi

Aerospace Engineering Publications

Elastocaloric cooling, which exploits the latent heat released and absorbed as stress-induced phase transformations are reversibly cycled in shape memory alloys, has recently emerged as a frontrunner in non-vapor-compression cooling technologies. The intrinsically high thermodynamic efficiency of elastocaloric materials is limited only by work hysteresis. Here, we report on creating high-performance low-hysteresis elastocaloric cooling materials via additive manufacturing of Titanium-Nickel (Ti-Ni) alloys. Contrary to established knowledge of the physical metallurgy of Ti-Ni alloys, intermetallic phases are found to be beneficial to elastocaloric performances when they are combined with the binary Ti-Ni compound in nanocomposite configurations. The resulting microstructure gives rise ...


Extensive Soot Compaction By Cloud Processing From Laboratory And Field Observations, Janarjan Bhandari, Swarup China, Kamal Kant Chandrakar, Greg Kinney, Will Cantrell, Raymond Shaw, Lynn Mazzoleni, Giulia Girotto, Noopur Sharma, Kyle Gorkowski, Stefania Gilardoni, Stefano Decesari, Maria Cristina Facchini, Nicola Zanca, Giulia Pavese, Francesco Esposito, Manvendra K Dubey, Allison C Aiken, Rajan K Chakrabarty, Hans Moosmüller, Timothy B Onasch, Rahul A Zaveri, Barbara V Scarnato, Paulo Fialho, Claudio Mazzoleni Aug 2019

Extensive Soot Compaction By Cloud Processing From Laboratory And Field Observations, Janarjan Bhandari, Swarup China, Kamal Kant Chandrakar, Greg Kinney, Will Cantrell, Raymond Shaw, Lynn Mazzoleni, Giulia Girotto, Noopur Sharma, Kyle Gorkowski, Stefania Gilardoni, Stefano Decesari, Maria Cristina Facchini, Nicola Zanca, Giulia Pavese, Francesco Esposito, Manvendra K Dubey, Allison C Aiken, Rajan K Chakrabarty, Hans Moosmüller, Timothy B Onasch, Rahul A Zaveri, Barbara V Scarnato, Paulo Fialho, Claudio Mazzoleni

Michigan Tech Publications

Soot particles form during combustion of carbonaceous materials and impact climate and air quality. When freshly emitted, they are typically fractal-like aggregates. After atmospheric aging, they can act as cloud condensation nuclei, and water condensation or evaporation restructure them to more compact aggregates, affecting their optical, aerodynamic, and surface properties. Here we survey the morphology of ambient soot particles from various locations and different environmental and aging conditions. We used electron microscopy and show extensive soot compaction after cloud processing. We further performed laboratory experiments to simulate atmospheric cloud processing under controlled conditions. We find that soot particles sampled after ...


Yang-Mills Sources For Biconformal Gravity, Walter Davis Muhwezi Aug 2019

Yang-Mills Sources For Biconformal Gravity, Walter Davis Muhwezi

Physics Capstone Project

We present a gauge formulation of Yang-Mills matter sources for Biconformal gravity. Biconformal gravity is a 2n-dimensional conformal gauge theory with a curvature linear action that has been shown to reproduce scale invariant general relativity on the cotangent bundle of n-dimensional space time. We present a generalization of Yang-Mills theories in biconformal space and show that the field equations with sources reduce the Yang-Mills sector to n-dimensional Yang-Mills theory in curved spacetime. We compute the restrictive conditions on the energy-momentum tensor required by the gravitational field equations.


Self-Consistent Two-Gap Description Of Mgb2 Superconductor, Hyunsoo Kim, Kyuil Cho, Makariy A. Tanatar, Valentin Taufour, Stella K. Kim, Sergey L. Bud’Ko, Paul C. Canfield, Vladimir G. Kogan, Ruslan Prozorov Aug 2019

Self-Consistent Two-Gap Description Of Mgb2 Superconductor, Hyunsoo Kim, Kyuil Cho, Makariy A. Tanatar, Valentin Taufour, Stella K. Kim, Sergey L. Bud’Ko, Paul C. Canfield, Vladimir G. Kogan, Ruslan Prozorov

Ames Laboratory Accepted Manuscripts

A self-consistent two-gap γ -model is used to quantitatively describe several thermodynamic properties of MgB 2 superconductor. The superconducting coupling matrix, νij , was obtained from the fitting of the superfluid density in the entire superconducting temperature range. Using this input, temperature-dependent superconducting gaps, specific heat, and upper critical fields were calculated with no adjustable parameters and compared with the experimental data as well as with the first-principles calculations. The observed agreement between fit and data shows that γ -model provides adequate quantitative description of the two-gap superconductivity in MgB 2 and may serve as a relatively simple and versatile self-consistent ...


Erratum: "Imaging The Three‐Dimensional Orientation And Rotational Mobility Of Fluorescent Emitters Using The Tri‐Spot Point Spread Function", Oumeng Zhang, Jin Lu, Tianben Ding, Matthew D. Lew Aug 2019

Erratum: "Imaging The Three‐Dimensional Orientation And Rotational Mobility Of Fluorescent Emitters Using The Tri‐Spot Point Spread Function", Oumeng Zhang, Jin Lu, Tianben Ding, Matthew D. Lew

Electrical & Systems Engineering Publications and Presentations

In the original paper, a calibration error exists in the image-formation model used to analyze experimental images taken by our microscope, causing a bias in the orientation measurements in Figs. 2 and 3. The updated measurements are shown in Fig. E1. We have also updated the supplementary material for the original article to discuss the revised PSF model and estimation algorithms (supplementary material 2) and show the revised model and measurements (Figs. S1, S3, S7, S8, and S10–S13).


Monitoring Ambient Laboratory Conditions With A Raspberry Pi, Joshua Boman Aug 2019

Monitoring Ambient Laboratory Conditions With A Raspberry Pi, Joshua Boman

Physics Capstone Project

Precise experimental devices and measurements can be sensitive to changing physical conditions in the lab. The purpose of this research was to develop a standardized computer automated package to monitor and record changes in laboratory conditions, including ambient temperature, atmospheric pressure, relative humidity, light intensity, motion, and power outages. The computer-interfaced device was based around an inexpensive Raspberry Pi microcomputer and commercially available sensors. The Raspberry Pi uploads the sensor data to a file used by LabVIEW to further analyze, plot and display the calibrated sensor data in real time and trigger alarms. This capability allows the Material Physics Research ...


Picosecond Time-Resolved Dynamics Of Energy Transfer Between Gan And The Various Excited States Of Eu3+ Ions, Ruoqiao Wei, Brandon Mitchell, Dolf Timmerman, Tom Gregorkiewicz, Wanxin Zhu, Jun Tatebayashi, Shuhei Ichikawa, Yasufumi Fujiwara, Volkmar Dierolf Aug 2019

Picosecond Time-Resolved Dynamics Of Energy Transfer Between Gan And The Various Excited States Of Eu3+ Ions, Ruoqiao Wei, Brandon Mitchell, Dolf Timmerman, Tom Gregorkiewicz, Wanxin Zhu, Jun Tatebayashi, Shuhei Ichikawa, Yasufumi Fujiwara, Volkmar Dierolf

Physics

To elucidate the energy transfer and reexcitation processes in Eu-doped GaN layers that are used in recently developed, highly efficient red light-emitting diodes, a systematic series of photoluminescence and time-resolved photoluminescence (TR-PL) measurements was performed. Critical insights on how “slow” Eu processes (∼µs) can compete against fast semiconductor processes (∼ps) are revealed using TR-PL with a high temporal resolution, as it is found that the initial energy transfer from GaN to the Eu3+ ions takes place rapidly, on a timescale of <100 ps. Below band-gap resonant excitation was used to identify the states into which the energy transfer occurs. For the most efficient Eu defect complexes, this transfer dominantly occurs directly into the 5 D0 state of Eu3+. Less efficient complexes also exhibit transfer into the 5 D2 state, the emission of which can be detected using photoluminescence at low temperature, indicating the importance of the excitation pathway on device efficiency. Under high excitation intensity, reexcitation can also occur, leading to a redistribution of population into the 5 D2, 5 D1, or 5 D0 states.


A Simple And Efficient Centrifugation Filtration Method For Bacterial Concentration And Isolation Prior To Testing Liquid Specimens With Laser-Induced Breakdown Spectroscopy, Dylan J. Malenfanta, Alexandra E. Paulick, Steven J. Rehse Aug 2019

A Simple And Efficient Centrifugation Filtration Method For Bacterial Concentration And Isolation Prior To Testing Liquid Specimens With Laser-Induced Breakdown Spectroscopy, Dylan J. Malenfanta, Alexandra E. Paulick, Steven J. Rehse

Physics Publications

An inexpensive filtration device was designed and constructed to rapidly concentrate bacteria in a liquid suspension on the surface of a disposable filter medium while at the same time separating the bacterial cells from larger contaminants in the suspension on the basis of their size. The device consists of a two-stage insert that is held rigidly in a standard tube during bacterial suspension centrifugation. The filters can be easily removed from the insert for subsequent testing with laser-induced breakdown spectroscopy in a process that takes only three minutes. Filter media of 0.45 micron pore size was found to capture ...


Computational Studies Of Thermal Properties And Desalination Performance Of Low-Dimensional Materials, Yang Hong Aug 2019

Computational Studies Of Thermal Properties And Desalination Performance Of Low-Dimensional Materials, Yang Hong

Student Research Projects, Dissertations, and Theses - Chemistry Department

During the last 30 years, microelectronic devices have been continuously designed and developed with smaller size and yet more functionalities. Today, hundreds of millions of transistors and complementary metal-oxide-semiconductor cells can be designed and integrated on a single microchip through 3D packaging and chip stacking technology. A large amount of heat will be generated in a limited space during the operation of microchips. Moreover, there is a high possibility of hot spots due to non-uniform integrated circuit design patterns as some core parts of a microchip work harder than other memory parts. This issue becomes acute as stacked microchips get ...


If Space-Time Is Discrete, We May Be Able To Solve Np-Hard Problems In Polynomial Time, Ricardo Alvarez, Nick Sims, Christian Servin, Martine Ceberio, Vladik Kreinovich Aug 2019

If Space-Time Is Discrete, We May Be Able To Solve Np-Hard Problems In Polynomial Time, Ricardo Alvarez, Nick Sims, Christian Servin, Martine Ceberio, Vladik Kreinovich

Departmental Technical Reports (CS)

Traditional physics assumes that space and time are continuous. However, this reasonable model leads to some serious problems. One the approaches that physicists follow to solve these problems is to assume that the space-time is actually discrete. In this paper, we analyze possible computational consequences of this discreteness. It turns out that in a discrete space-time, we may be able to solve NP-hard problems in polynomial time.


Avoiding Einstein-Podolsky-Rosen (Epr) Paradox: Towards A More Physically Adequate Description Of A Quantum State, Joseph Bernal, Olga Kosheleva, Vladik Kreinovich Aug 2019

Avoiding Einstein-Podolsky-Rosen (Epr) Paradox: Towards A More Physically Adequate Description Of A Quantum State, Joseph Bernal, Olga Kosheleva, Vladik Kreinovich

Departmental Technical Reports (CS)

The famous EPR paradox shows that if we describe quantum particles in the usual way -- by their wave functions -- then we get the following seeming contradiction. If we entangle the states of the two particles, then move them far away from each other, and measure the state of the first particle, then the state of the second particle immediately changes -- which contradicts to special relativity, according to which such immediate-action-at-a-distance is not possible. It is known that, from the physical viewpoint, this is not a real paradox: if we measure any property of the second particle, the results will not ...


Benchmarks Of Nonclassicality For Qubit Arrays, Mordecai Waegell, Justin Dressel Aug 2019

Benchmarks Of Nonclassicality For Qubit Arrays, Mordecai Waegell, Justin Dressel

Mathematics, Physics, and Computer Science Faculty Articles and Research

We present a set of practical benchmarks for N-qubit arrays that economically test the fidelity of achieving multi-qubit nonclassicality. The benchmarks are measurable correlators similar to two-qubit Bell correlators, and are derived from a particular set of geometric structures from the N-qubit Pauli group. These structures prove the Greenberger–Horne–Zeilinger (GHZ) theorem, while the derived correlators witness genuine N-partite entanglement and establish a tight lower bound on the fidelity of particular stabilizer state preparations. The correlators need only MN + 1 distinct measurement settings, as opposed to the 22N − 1 settings that would normally be required ...


Inverse Design Of Long-Range Intensity Correlation In Scattering Media, M. Koirala, R. Sarma, H. Cao, Alexey Yamilov Aug 2019

Inverse Design Of Long-Range Intensity Correlation In Scattering Media, M. Koirala, R. Sarma, H. Cao, Alexey Yamilov

Physics Faculty Research & Creative Works

We demonstrate a possibility of using geometry to deterministically control nonlocal correlation of waves undergoing mesoscopic transport through a disordered waveguide. In case of nondissipative medium, we find an explicit relationship between correlation and the shape of the system. Inverting this relationship, we realize inverse design: we obtain specific waveguide shape that leads to a predetermined nonlocal correlation. The proposed technique offers an approach to coherent control of wave propagation in random media that is complementary to wave-front shaping.


Hole Doping And Antiferromagnetic Correlations Above The Néel Temperature Of The Topological Semimetal (Sr1-X Kx) Mnsb2, Yong Liu, Farhan Islam, Kevin W. Dennis, Wei Tian, Benjamin G. Ueland, Robert J. Mcqueeney, David Vaknin Jul 2019

Hole Doping And Antiferromagnetic Correlations Above The Néel Temperature Of The Topological Semimetal (Sr1-X Kx) Mnsb2, Yong Liu, Farhan Islam, Kevin W. Dennis, Wei Tian, Benjamin G. Ueland, Robert J. Mcqueeney, David Vaknin

Ames Laboratory Accepted Manuscripts

Neutron diffraction and magnetic susceptibility studies of orthorhombic single crystal (Sr0.97K0.03)MnSb2 confirm the three-dimensional (3D) C-type antiferromagnetic (AFM) ordering of the Mn2+ moments at TN=305±3 K, which is slightly higher than that of the parent SrMnSb2 with TN=297±3 K. Susceptibility measurements of the K-doped and parent crystals above TN are characteristic of 2D AFM systems. This is consistent with high-temperature neutron diffraction of the parent compound that displays persisting 2D AFM correlations well above TN to at least ∼560 K with no evidence of a ferromagnetic phase. Analysis of the de Haas–van ...


Stereodynamical Control Of A Quantum Scattering Resonance In Cold Molecular Collisions, Pablo G. Jambrina, James F.E. Croft, Hua Guo, Mark Brouard, Balakrishnan Naduvalath, F. Javier Aoiz Jul 2019

Stereodynamical Control Of A Quantum Scattering Resonance In Cold Molecular Collisions, Pablo G. Jambrina, James F.E. Croft, Hua Guo, Mark Brouard, Balakrishnan Naduvalath, F. Javier Aoiz

Chemistry and Biochemistry Faculty Publications

Cold collisions of light molecules are often dominated by a single partial wave resonance. For the rotational quenching of HD (v=1, j=2) by collisions with ground state para-H2, the process is dominated by a single L=2 partial wave resonance centered around 0.1 K. Here, we show that this resonance can be switched on or off simply by appropriate alignment of the HD rotational angular momentum relative to the initial velocity vector, thereby enabling complete control of the collision outcome.


Temperature-Dependent Anisotropies Of Upper Critical Field And London Penetration Depth, V. G. Kogan, Ruslan Prozorov, A. E. Koshelev Jul 2019

Temperature-Dependent Anisotropies Of Upper Critical Field And London Penetration Depth, V. G. Kogan, Ruslan Prozorov, A. E. Koshelev

Ames Laboratory Accepted Manuscripts

We show on a few examples of one-band materials with spheroidal Fermi surfaces and anisotropic order parameters that anisotropies γH of the upper critical field and γλ of the London penetration depth depend on temperature, a feature commonly attributed to multiband superconductors. The parameters γH and γλ may have opposite temperature dependences or may change in the same direction depending on the Fermi-surface shape and on the character of the gap nodes. For two-band systems, the behavior of anisotropies is affected by the ratios of bands densities of states, Fermi velocities, anisotropies, and order parameters. We investigate in detail the ...


The Delay Time Of Gravitational Wave — Gamma-Ray Burst Associations, Bing Zhang Jul 2019

The Delay Time Of Gravitational Wave — Gamma-Ray Burst Associations, Bing Zhang

Physics & Astronomy Faculty Publications

The first gravitational wave (GW) — gamma-ray burst (GRB) association, GW170817/GRB 170817A, had an offset in time, with the GRB trigger time delayed by ∼1.7 s with respect to the merger time of the GW signal. We generally discuss the astrophysical origin of the delay time, Δt, of GW-GRB associations within the context of compact binary coalescence (CBC) — short GRB (sGRB) associations and GW burst — long GRB (lGRB) associations. In general, the delay time should include three terms, the time to launch a clean (relativistic) jet, Δtjet; the time for the jet to break out from the surrounding medium ...


Single-Neutron States In Titanium Isotopes, Jessica Nebel-Crosson Jul 2019

Single-Neutron States In Titanium Isotopes, Jessica Nebel-Crosson

Physics and Astronomy Summer Fellows

Current theory regarding the collective behavior of exotic nuclei systematically over-predicts the probabilities of exciting those collective states. The theory lacks any adjustable parameters, however, the model inputs are characteristics of single particle states which we are attempting to verify through neutron transfer into a 50Ti target.


Improving Simulations Of The Gretina Gamma-Ray Tracking Array, Esther Lawson-John Jul 2019

Improving Simulations Of The Gretina Gamma-Ray Tracking Array, Esther Lawson-John

Physics and Astronomy Summer Fellows

The GRETINA gamma-ray tracking array is an array of gamma-ray detectors that is being used by the nuclear structure community physicists to analyze properties of atomic nuclei. The problem is that when we compare measurements to simulations we see that the simulation is more efficient than the real array. This led us to investigate the size and shape of inactive volumes in the detectors by comparing our simulations with measurements made at Lawrence Berkeley National Laboratory with a pencil beam of gamma rays in order to improve our model of the detectors. Upon investigating these different avenues, the aim is ...


Anisotropy And Orbital Moment In Sm-Co Permanent Magnets, Bhaskar Das, Renu Choudhary, Ralph Skomski, Balamurugan Balasubramanian, Arjun K. Pathak, Durga Paudyal, David J. Sellmyer Jul 2019

Anisotropy And Orbital Moment In Sm-Co Permanent Magnets, Bhaskar Das, Renu Choudhary, Ralph Skomski, Balamurugan Balasubramanian, Arjun K. Pathak, Durga Paudyal, David J. Sellmyer

Ames Laboratory Accepted Manuscripts

Structural and magnetic properties of iron-free and iron-substituted SmCo5 have been investigated theoretically and experimentally. The nanocrystalline ribbons of SmCo5−xFex(0≤x≤2), which were produced by rapid solidification, crystallize in the hexagonal CaCu5 structure for x≤0.75. Small Fe additions (x=0.25) substantially improve the coercivity, from 0.45 to 2.70 T, which we interpret as combined intrinsic and extrinsic effect. Most of our findings are consistent with past samarium-cobalt research, but some are at odds with findings that have seemingly been well established through decades of rare-earth transition-metal research. In particular, our local spin-density ...


Games: Glass And Materials Science To Engage Students, M. A. Liggett, Kateryna Swan Jul 2019

Games: Glass And Materials Science To Engage Students, M. A. Liggett, Kateryna Swan

Physics and Astronomy Summer Fellows

Materials science is the study of the properties of matter and its applications in optics, chemistry, physics, and civil, electrical, chemical, and mechanical engineering. The broad field of materials science and the complex ideas that can be included in it are typically introduced into formal education at the college level, but recently there has been a push for younger students to also have exposure to materials science. In this project, we used the techniques demonstrated in First Physics to expose students, ages 9-15, to materials science. Our hypothesis was that by using these techniques, higher level concepts can be broken ...


Search For Resonant Double Higgs Production With Bbzz Decays In The Bbℓℓνν Final State In Pp Collisions At √S = 13 Tev, Rami Kamalieddin Jul 2019

Search For Resonant Double Higgs Production With Bbzz Decays In The Bbℓℓνν Final State In Pp Collisions At √S = 13 Tev, Rami Kamalieddin

Theses, Dissertations, and Student Research: Department of Physics and Astronomy

Since the discovery of the Higgs boson in 2012 by the ATLAS and CMS experiments, most of the quantum mechanical properties that describe the long-awaited Higgs boson have been measured. Due to the outstanding work of the LHC, over a hundred of fb−1 of proton collisions data have been delivered to both experiments. Finally, it became sensible for analyses teams to start working with a very low cross section processes involving the Higgs boson, e.g., a recent success in observing ttH and VHbb processes. One of the main remaining untouched topics is a double Higgs boson production. However ...


Antiferromagnetic Stacking Of Ferromagnetic Layers And Doping-Controlled Phase Competition In Ca1−X Srx Co2−Y As2, Bing Li, Yuriy Sizyuk, Nediadath S. Sangeetha, John M. Wilde, Pinaki Das, W. Tian, David C. Johnston, Alan I. Goldman, Andreas Kreyssig, Peter P. Orth, Robert J. Mcqueeney, Benjamin G. Ueland Jul 2019

Antiferromagnetic Stacking Of Ferromagnetic Layers And Doping-Controlled Phase Competition In Ca1−X Srx Co2−Y As2, Bing Li, Yuriy Sizyuk, Nediadath S. Sangeetha, John M. Wilde, Pinaki Das, W. Tian, David C. Johnston, Alan I. Goldman, Andreas Kreyssig, Peter P. Orth, Robert J. Mcqueeney, Benjamin G. Ueland

Ames Laboratory Accepted Manuscripts

In search of a quantum phase transition between the two-dimensional (2D) ferromagnetism of CaCo2−yAs2 and stripe-type antiferromagnetism in SrCo2 As2, we instead find evidence for 1D magnetic frustration between magnetic square Co layers. We present neutron-diffraction data for Ca1−x Srx Co2−y As2 that reveal a sequence of x -dependent magnetic transitions which involve different stacking of 2 D ferromagnetically aligned layers with different magnetic anisotropy. We explain the x-dependent changes to the magnetic order by utilizing classical analytical calculations of a 1D Heisenberg model where single-ion magnetic anisotropy and frustration of antiferromagnetic nearest- and next-nearest-layer exchange interactions ...


Topological Nodal Line Semimetals In Graphene Network Structures, Jian-Tao Wang, Hongming Weng, Chengfeng Chen Jul 2019

Topological Nodal Line Semimetals In Graphene Network Structures, Jian-Tao Wang, Hongming Weng, Chengfeng Chen

Physics & Astronomy Faculty Publications

Topological semimetals are a fascinating class of quantum materials that possess extraordinary electronic and transport properties. These materials have attracted great interests in recent years for their fundamental significance and potential device applications. There have been intensive studies suggested that three-dimensional graphene networks support topological semimetals with two types of continuous nodal lines: one is to form closed nodal rings in Brillouin zone and the other ones traversing the whole Brillouin zone to be periodically connected. Carbon has negligible spin-orbit coupling, non-magnetism and great diversity of allotropes, which makes it very promising in realizing topological nodal line semimetals. Here we ...


Tuning Phase-Stability And Short-Range Order Through Ai-Doping In (Cocrfemn)100-Xaix High Entropy Alloys, Prashant Singh, Amalraj Marshal, A. V. Smirnov, Aayush Sharma, Ganesh Balasubramanian, K. G. Pradeep, Duane D. Johnson Jul 2019

Tuning Phase-Stability And Short-Range Order Through Ai-Doping In (Cocrfemn)100-Xaix High Entropy Alloys, Prashant Singh, Amalraj Marshal, A. V. Smirnov, Aayush Sharma, Ganesh Balasubramanian, K. G. Pradeep, Duane D. Johnson

Ames Laboratory Accepted Manuscripts

For (CoCrFeMn)100−xAlx high-entropy alloys, we investigate the phase evolution with increasing Al content (0≤x≤20 at.%). From first-principles theory, aluminum doping drives the alloy structurally from fcc to bcc separated by a narrow two-phase region (fcc+bcc), which is well supported by our experiments. Using KKR-CPA electronic-structure calculations, we highlight the effect of Al doping on the formation enthalpy (alloy stability) and electronic dispersion of (CoCrFeMn)100−xAlx alloys. As chemical short-range order indicates the nascent local order, and entropy changes, as well as expected low-temperature ordering behavior, we use KKR-CPA-based thermodynamic linear response to predict the ...


Interplay Between Superconductivity And Itinerant Magnetism In Underdoped Ba1−Xkxfe2as2 (X = 0.2) Probed By The Response To Controlled Point-Like Disorder, Ruslan Prozorov, Marcin Kończykowski, Makariy A. Tanatar, Hai-Hu Wen, Rafael M. Fernandes, Paul C. Canfield Jul 2019

Interplay Between Superconductivity And Itinerant Magnetism In Underdoped Ba1−Xkxfe2as2 (X = 0.2) Probed By The Response To Controlled Point-Like Disorder, Ruslan Prozorov, Marcin Kończykowski, Makariy A. Tanatar, Hai-Hu Wen, Rafael M. Fernandes, Paul C. Canfield

Ames Laboratory Accepted Manuscripts

The response of superconductors to controlled introduction of point-like disorder is an important tool to probe their microscopic electronic collective behavior. In the case of iron-based superconductors, magnetic fluctuations presumably play an important role in inducing high-temperature superconductivity. In some cases, these two seemingly incompatible orders coexist microscopically. Therefore, understanding how this unique coexistence state is affected by disorder can provide important information about the microscopic mechanisms involved. In one of the most studied pnictide family, hole-doped Ba1−xKxFe2As2 (BaK122), this coexistence occurs over a wide range of doping levels, 0.16 ≲ x ≲ 0.25. We used ...


Laser Cooling With Adiabatic Transfer On A Raman Transition, Graham Greve, Baochen Wu, James K. Thompson Jul 2019

Laser Cooling With Adiabatic Transfer On A Raman Transition, Graham Greve, Baochen Wu, James K. Thompson

JILA Faculty Contributions

Sawtooth Wave Adiabatic Passage (SWAP) laser cooling was recently demonstrated using a narrow-linewidth single-photon optical transition in atomic strontium and may prove useful for cooling other atoms and molecules. However, many atoms and molecules lack the appropriate narrow optical transition. Here we use such an atom, 87Rb, to demonstrate that two-photon Raman transitions with arbitrarily-tunable linewidths can be used to achieve 1D SWAP cooling without significantly populating the intermediate excited state. Unlike SWAP cooling on a narrow transition, Raman SWAP cooling allows for a final 1D temperature well below the Doppler cooling limit (here, 25 times lower); and the ...


Concentration Of Bacterial Specimens During Centrifugation Prior To Laser-Induced Breakdown Spectroscopy Analysis, Alexandra E. Paulicka, Dylan J. Malenfanta, Steven J. Rehse Jul 2019

Concentration Of Bacterial Specimens During Centrifugation Prior To Laser-Induced Breakdown Spectroscopy Analysis, Alexandra E. Paulicka, Dylan J. Malenfanta, Steven J. Rehse

Physics Publications

A metal cone device has been designed and fabricated for use with a custom centrifuge tube insert to allow the simple and rapid concentration of bacterial cells in a circular area with a diameter of 1 mm. The device concentrates cells suspended in up to 1 mL of liquid at the center of a highly flat disposable filter medium which can be easily removed from the centrifuge tube insert for subsequent testing with laser-induced breakdown spectroscopy. Two-dimensional elemental mapping of the filter evidenced a high concentration of bacteria on the filter under the location of the cone hole, as well ...


Using Forensics To Introduce Ir Spectroscopy & Molecular Modeling, Joe Golab Jul 2019

Using Forensics To Introduce Ir Spectroscopy & Molecular Modeling, Joe Golab

Faculty Publications & Research

A student activity is reported that analyzes “medical evidence” with experimental and computational methods. The lesson demonstrates benefits of solving practical problems with integrated tools.