Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session J03: Materials in Extremes: Novel Materials and Phenomena at Extreme ConditionsFocus
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Sponsoring Units: GSCCM Chair: Elissaios Stavrou, Lawrence Livermore Natl Lab Room: 107 |
Tuesday, March 3, 2020 2:30PM - 3:06PM |
J03.00001: Novel experimental approaches toward metastable materials discovery under pressure Invited Speaker: James Walsh High pressure is a powerful synthetic tool that enables the discovery of novel materials with unprecedented bonding, crystal structure, and bulk properties. We are developing experimental methods that provide chemists with access to regions of high-pressure phase space that are currently difficult to explore. Examples include methods to target specific elemental compositions in ternary systems where competing binary phases are a complication, or techniques to kinetically stabilize high-pressure phases that do not survive traditional decompression routes. Our work is underpinned by state-of-the-art DFT packages that allow us to explore systems in search of candidate high-pressure phases and determine their formation conditions before even stepping into the lab. I will present recent results that highlight the growing synergy between cutting-edge computational methods and novel experimental approaches. |
Tuesday, March 3, 2020 3:06PM - 3:18PM |
J03.00002: New materials under extreme environments Wendy Mao The application of extreme environments (including variable pressure, temperature and irradiation) can induce dramatic changes in materials and give us a much broader field to discover new phases and explore novel phenomena. Improving our understanding of the modifications that occur can also provide guidance for designing improved materials with desirable properties that can be utilized for energy-related applications. I will presenting some examples which demonstrate the range of new materials that can be formed and properties which can be altered under extreme environments. In particular, I will focus on experimental work using high pressure as promising variable for tuning materials behavior. |
Tuesday, March 3, 2020 3:18PM - 3:30PM |
J03.00003: Detection of High-Pressure Electride Phases with X-ray Diffraction: A First Principles Analysis Rafi Ullah, Stanimir Bonev The direct experimental detection of high pressure electride phases of matter is a challenging problem. It was suggested that the interstitial localization of valence electrons - a signature of the electride phase - could be detected in the x-ray diffraction experiments. We have used first-principles calculations to quantify detectable changes in the x-ray scattering patterns of high pressure electrides. A comparison of the electron localization function and the first principles charge density to corroborate the nature and extent of interstitial electron localization will be discussed as well. |
Tuesday, March 3, 2020 3:30PM - 3:42PM |
J03.00004: High-pressure chemistry of transition metal polynitrides Maxim Bykov, Stella Chariton, Elena Bykova, Mohammad Mahmood, Alexander Goncharov, Leonid Dubrovinsky The high-pressure chemistry of nitrogen and nitrogen-rich compounds have been in a focus of many studies in the recent years due to both fundamental and practical interest and due to the improvement of high-pressure synthetic and characterization techniques. Poly-nitrogen compounds are usually considered as potential high energy density materials (HEDM) due to the remarkable difference in the average bond energy between the single N–N bond, the double N=N bond , and the triple N≡N bond. Numerous polynitrogen compounds with various nitrogen polymeric networks were theoretically predicted, but there are only a very few experimental attempts to obtain such compounds. |
Tuesday, March 3, 2020 3:42PM - 3:54PM |
J03.00005: Formation of XeN4 at high pressure-high temperature conditions Maddury Somayazulu, Alexander Goncharov, Yue Meng, Jesse Smith, Watkins B Erik, Dana Dattelbaum, Russell J Hemley Mixtures of xenon and nitrogen have been observed to form a cubic, van der Waals compound Xe(N2)2 at pressures above 2 GPa in concurrence with the study reported to pressures above 150 GPa [1,2]. The existence of the z phase of nitrogen [3] and hcp xenon [4] could be inferred from x-ray diffraction. The sample becomes opaque above 170 GPa and could be laser heated quite easily. In contrast to what is reported for pure N2 [5], a new phase forms when the sample was laser heated above 2800 K and above 160 GPa. This phase is identified to be monoclinic and has distinctive Raman signatures that can be ascribed to the existence of N4 units which are linear and double bonded. This is at variance to the theoretical prediction of cubic XeN6 [6]. We will report the details of the spectroscopy (Raman and FTIR) as well as synchrotron powder diffraction analysis of this potentially energetic nitride of xenon. |
Tuesday, March 3, 2020 3:54PM - 4:06PM |
J03.00006: High Magnetic Field Probe of Hydride Superconductors Fedor Balakirev, Dan Sun, Jonathan B Betts, Shirin Mozaffari, Luis Balicas, Mari Einaga, Katsuya Shimizu, Vasily S Minkov, Panpan Kong, Dmitry Knyazev, Alexander Drozdov, Mikhail Eremets High magnetic fields have proven to be an invaluable tool for exploring properties of novel superconductors. A combination of miniature diamond anvil cells and pulse magnets allows us to controllably tune and probe the superconducting order and the vortex matter in several recently discovered hydride superconductors at the extremes of pressure-field parameter envelope. Because of the larger superconducting energy scale, magnetic fields of the order of 100 T are required to establish key superconducting properties, including Cooper pair coherence length, the strength of the electron-phonon coupling, the role of the spin-orbit coupling, and the dominant mechanism breaking the Copper pairs. We find that the orbital effect suppresses superconductivity over the entire temperature range, while pronounced deviations from the Werthamer, Helfand, and Hohenberg theory predictions are observed at lower temperatures. |
Tuesday, March 3, 2020 4:06PM - 4:18PM |
J03.00007: High-pressure studies of magnetism on EuAFe4As4 (A=Rb, Cs) via synchrotron Mössbauer spectroscopy Wenli Bi, Philipp Materne, jiyong zhao, Esen E. Alp, Jin-Ke Bao, Yi Liu, Guang-Han Cao EuAFe4As4(A=Rb, Cs) is a recent addition to the iron-based superconductors. EuAFe4As4exhibits peculiar properties with coexistence of superconductivity (TC ~ 35 K) and ferromagnetism from local moment in divalent Eu (Tm~15 K) [1–4]. The application of pressure suppresses superconductivity and enhance magnetic ordering temperature [5,6] with a crossover of TC and Tm around 7 GPa [5]. We have investigated the magnetic and valence state in Eu ions via synchrotron Mössbauer spectroscopy in 151Eu in diamond anvil cell. The detailed changes of Eu’s magnetism and local magnetic phase diagram will be discussed. |
Tuesday, March 3, 2020 4:18PM - 4:30PM |
J03.00008: Understanding EuD4TEA and its Use as Impact or Radiation Sensors in Extreme Environments John Miller, William A. Hollerman, Karili Tolga, Alyssa V. Bienvenu If humans desire to leave the safety of Earth and explore extreme environments, cost effective and low mass health monitoring sensors will be essential to monitor impacts or incident ionizing radiation as they travel. To ensure the safety of the astronauts, a luminescent material-based sensor might be used to provide reliable in-situ impact detection or radiation monitoring for space vehicles. An extensive research program has been completed to date where many luminescent materials have been irradiated with protons and electrons. Results have generally shown that charged particle irradiation reduces the intensity of emitted luminescence by producing quenching centers. Related research has also shown that some of the same materials will emit copious light in the form of triboluminescence when crushed or struck. This paper investigates the effects of impacts or radiation on europium tetrakis dibenzoylmethide triethylammonium (EuD4TEA). Special emphasis will be placed on our work to better understand the structure and composition of EuD4TEA. This research can be used to help determine if luminescent materials can be used as an impact or radiation sensor in extreme environments like space. |
Tuesday, March 3, 2020 4:30PM - 4:42PM |
J03.00009: “Persistent” Insulator: Avoidance of Metallization at Megabar Pressures in Strongly Spin-Orbit-Coupled Sr2IrO4 Zhaorong Yang, Chunhua Chen, Yonghui Zhou, Gang Cao Here we report a rare insulating state that persists up to at least 185 GPa in the antiferromagnetic iridate Sr2IrO4, which is the archetype of a spin-orbit-driven Jeff = 1/2 insulators. This study shows the electrical resistance of single-crystal Sr2IrO4 decreases initially with pressure, then reaches a minimum in the range, 32 - 38 GPa, and is followed by a rapid rise to fully recover the insulating state (~107 W) with further pressure increases up to 185 GPa. The onset of the rapid increase in resistance is accompanied by a structural phase transition from the native tetragonal I41/acd phase to an orthorhombic Pbca phase (with much reduced symmetry) at 40.6 GPa, according to our synchrotron x-ray diffraction and Raman scattering data. This close correlation explains the existence of the rare insulating state at megabar pressures: the pressure-induced, severe structural distortions prevent expected metallization, despite a 26% volume compression in Sr2IrO4 at the highest pressure accessed in this experiment. It is striking that the high electrical resistance remains essentially unchanged with a tripling of very high pressure range from 61 GPa to 185 GPa. |
Tuesday, March 3, 2020 4:42PM - 4:54PM |
J03.00010: Pressure-Induced novel properties in Several Topological Materials. Xiangang Wan Topological materials, exemplified by the topological insulators and nodal semimetals, showcase intriguing physical properties which could not emerge had electrons been classical particles. Recently the effect of high pressure on these materials has also attracted much attention. We will discuss our results in several topological materials. |
Tuesday, March 3, 2020 4:54PM - 5:06PM |
J03.00011: Hydrostatic pressure effect on several superconductors: 1T-&2H-Ta(S,Se)2 and (Ba, Sr)Bi3 Bosen Wang, Jinguang Cheng, Yuping Sun, Yoshiya Uwatoko Under high hydrostatic pressure in Cubic Anvil Pressure Apparent, we revealed the universal phase diagram of superconductivity and charge density wave (CDW) for 1T- and 2H-Ta(S,Se)2 by electrical transport and ac susceptibility. For 1T-, CDWs and SC coexists in narrow pressure windows and superconducting transition temperature (Tc) increases monotonously, clarifying that the superconducting cooper-pairing is associated with CDW instability [1, 2]. For 2H-, CDWs and SC coexists in a real sapce and Tc tends to saturation at critical pressures. Possible physical mechanisms are proposed. Besides, we firstly reported pressured-induced crossover from Type-II to Type-I superconductivity in spin-orbit-coupled SCs (Ba, Sr)Bi3 [3]. |
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J03.00012: High-pressure synthesis and pressure-induced spin, charge and lattice transitions of PbCoO3 Youwen Long By using a peculiar high-pressure and high-temperature method, we for the first time prepared PbCoO3 [1]. It crystallizes into an A-site and B-site ordered quadruple perovskite structure with space group of Pn-3. The charge combination is confirmed to be Pb2+Pb4+3Co2+2Co3+3O12, where the Co2+ is high spin while the Co3+ is low spin. Although only Co2+ is magnetic, the compound experiences two antiferromagnetic transitions. More interestingly, when external pressure is applied, the high spin Co2+ gradually changes to low spin with pressure up to 15 GPa. Between 15 and 30 GPa, the intermetallic charge transfer occurs between Pb4+ and Co2+. The accumulated charge-transfer effect triggers a metal-insulator transition as well as a first-order structural phase transition toward a Tetra.-I phase at ~20 GPa near room temperature. On further compression over 30 GPa, the charge transfer completes, leading to another first-order structural transformation toward a Tetra.-II phase and the reentrant electrical insulating behavior. |
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J03.00013: Computational prediction of correlated iron compounds at high pressure and experimental synthesis Duck Young Kim Iron is one of key elements in our contemporary technology and the backbone element of the Earth. Study on pure iron and iron-compounds in extreme conditions is important and finding new iron compounds is particularly of our interest. In this talk, I will present recent progress in finding new iron compounds at high pressure. Computationally we used ab initio structure searching strategies to predict the compositions and crystal structures based on density functional theory, which were successfully synthesized by experiments [1,2]. Dynamic mean field theory provides more precise description for the electronic structure of the predicted compounds by revealing metal-insulator transition, and spin transition induced by pressure [3, 4]. I will also discuss possible implications for geoscience of these studies [5]. |
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