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Ames Laboratory Accepted Manuscripts

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Full-Text Articles in Physics

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 ...


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 ...


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 ...


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 ...


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 ...


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 ...


Single Pair Of Weyl Fermions In The Half-Metallic Semimetal Eucd2as2, Lin-Lin Wang, Na Hyun Jo, Brinda Kuthanazhi, Yun Wu, Robert J. Mcqueeney, Adam Kaminski, Paul C. Canfield Jun 2019

Single Pair Of Weyl Fermions In The Half-Metallic Semimetal Eucd2as2, Lin-Lin Wang, Na Hyun Jo, Brinda Kuthanazhi, Yun Wu, Robert J. Mcqueeney, Adam Kaminski, Paul C. Canfield

Ames Laboratory Accepted Manuscripts

Materials with the ideal case of a single pair of Weyl points (WPs) are highly desirable for elucidating the unique properties of Weyl fermions. EuC d 2 A s 2 is an antiferromagnetic topological insulator or Dirac semimetal depending on the different magnetic configurations. Using first-principles band-structure calculations, we show that inducing ferromagnetism in EuC d 2 A s 2 can generate a single pair of WPs from splitting the single pair of antiferromagnetic Dirac points due to its half-metallic nature. Analysis with a low-energy effective Hamiltonian shows that a single pair of WPs is obtained in EuC d 2 ...


Magnetic Structure And Magnetization Of Z -Axis Helical Heisenberg Antiferromagnets With Xy Anisotropy In High Magnetic Fields Transverse To The Helix Axis At Zero Temperature, David C. Johnston Jun 2019

Magnetic Structure And Magnetization Of Z -Axis Helical Heisenberg Antiferromagnets With Xy Anisotropy In High Magnetic Fields Transverse To The Helix Axis At Zero Temperature, David C. Johnston

Ames Laboratory Accepted Manuscripts

A helix has a wave vector along the z axis with the magnetic moments ferromagnetically aligned within xy planes with a turn angle kd between the moments in adjacent planes in transverse field H=Hxˆi=0. The magnetic structure and x-axis average magnetization per spin of this system in a classical XY anisotropy field HA is studied versus kd, HA, and large Hx at zero temperature. For values of HA below a kd-dependent maximum value, the xy helix phase transitions with increasing Hx into a spin-flop (SF) phase where the ordered moments have x, y, and z components. The moments ...


Two-Dimensional Ordering And Collective Magnetic Excitations In The Dilute Ferromagnetic Topological Insulator (Bi0.95 Mn0.05)2 Te3, David Vaknin, Daniel M. Pajerowski, Deborah L. Schlagel, Kevin W. Dennis, Robert Mcqueeney Jun 2019

Two-Dimensional Ordering And Collective Magnetic Excitations In The Dilute Ferromagnetic Topological Insulator (Bi0.95 Mn0.05)2 Te3, David Vaknin, Daniel M. Pajerowski, Deborah L. Schlagel, Kevin W. Dennis, Robert Mcqueeney

Ames Laboratory Accepted Manuscripts

Employing elastic and inelastic neutron scattering (INS) techniques, we report on the microscopic properties of the ferromagnetism in the dilute magnetic topological insulator (Bi0.95Mn0.05)2 Te3. Neutron diffraction of polycrystalline samples shows the ferromagnetic (FM) ordering is long range within the basal plane, and mainly two dimensional (2D) in character with short-range correlations between layers below T C ≈ 13 K. Remarkably, we observe gapped and collective magnetic excitations in this dilute magnetic system. The excitations appear typical of quasi-2D FM systems despite the severe broadening of short-wavelength magnons which is expected from the random spatial distribution of Mn ...


Ultrahigh Elastically Compressible And Strain-Engineerable Intermetallic Compounds Under Uniaxial Mechanical Loading, Gyuho Song, Vladislav Borisov, William Meier, Mingyu Xu, Keith J. Dusoe, John T. Sypek, Roser Valentí, Paul C. Canfield, Seok-Woo Lee Jun 2019

Ultrahigh Elastically Compressible And Strain-Engineerable Intermetallic Compounds Under Uniaxial Mechanical Loading, Gyuho Song, Vladislav Borisov, William Meier, Mingyu Xu, Keith J. Dusoe, John T. Sypek, Roser Valentí, Paul C. Canfield, Seok-Woo Lee

Ames Laboratory Accepted Manuscripts

Intermetallic compounds possess unique atomic arrangements that often lead to exceptional material properties, but their extreme brittleness usually causes fracture at a limited strain of less than 1% and prevents their practical use. Therefore, it is critical for them to exhibit either plasticity or some form of structural transition to absorb and release a sufficient amount of mechanical energy before failure occurs. This study reports that the ThCr2Si2-structured intermetallic compound (CaFe2As2) and a hybrid of its structure (CaKFe4As4) with 2 µm in diameter and 6 µm in height can exhibit superelasticity with strain up to 17% through a reversible, deformation-induced ...


Topological States In A15 Superconductors, Minsung Kim, Cai-Zhuang Wang, Kai-Ming Ho Jun 2019

Topological States In A15 Superconductors, Minsung Kim, Cai-Zhuang Wang, Kai-Ming Ho

Ames Laboratory Accepted Manuscripts

Superconductors with the A15 structure are prototypical type-II s-wave superconductors which have generated considerable interest in early superconducting material history. However, the topological nature of the electronic structure remains unnoticed so far. Here, using first-principles band structure calculations based on density-functional theory, we show that the A15 superconductors (Ta3Sb, Ta3Sn, and Ta3Pb) have nontrivial band topology in the bulk electronic band structures, leading to the formation of topological surface states near the Fermi energy. Due to the bulk superconductivity, the proximity effect in the topological surface states would induce topological superconductivity even without heterostructure of a topological insulator and an ...


Magnetic Fluctuations In The Itinerant Ferromagnet Lacrge3 Studied By 139la Nmr, K. Rana, H. Kotegawa, R. R. Ullah, J. S. Harvey, Sergey L. Bud’Ko, Paul C. Canfield, H. Tou, V. Taufour, Yuji Furukawa Jun 2019

Magnetic Fluctuations In The Itinerant Ferromagnet Lacrge3 Studied By 139la Nmr, K. Rana, H. Kotegawa, R. R. Ullah, J. S. Harvey, Sergey L. Bud’Ko, Paul C. Canfield, H. Tou, V. Taufour, Yuji Furukawa

Ames Laboratory Accepted Manuscripts

LaCrGe3 is an itinerant ferromagnet with a Curie temperature of T C = 85 K and exhibits an avoided ferromagnetic quantum critical point under pressure through a modulated antiferromagnetic phase as well as tricritical wing structure in its temperature-pressure-magnetic field ( T – p – H) phase diagram. In order to understand the static and dynamical magnetic properties of LaCrGe3 , we carried out 139 La nuclear magnetic resonance (NMR) measurements. Based on the analysis of NMR data, using the self-consistent-renormalization (SCR) theory, the spin fluctuations in the paramagnetic state are revealed to be isotropic ferromagnetic and three dimensional (3D) in nature. Furthermore, the system ...


Crystal Growth And Magnetic Structure Of Mnbi2 Te 4, J.-Q. Yan, Q. Zhang, T. Heitmann, Zengle Huang, K. Y. Chen, J.-G. Cheng, Weida Wu, David Vaknin, B. C. Sales, Robert J. Mcqueeney Jun 2019

Crystal Growth And Magnetic Structure Of Mnbi2 Te 4, J.-Q. Yan, Q. Zhang, T. Heitmann, Zengle Huang, K. Y. Chen, J.-G. Cheng, Weida Wu, David Vaknin, B. C. Sales, Robert J. Mcqueeney

Ames Laboratory Accepted Manuscripts

Millimeter-sized MnBi2Te4 single crystals are grown out of a Bi-Te flux and characterized using magnetic, transport, scanning tunneling microscopy, and spectroscopy measurements. The magnetic structure of MnBi2Te4 below TN is determined by powder and single-crystal neutron diffraction measurements. Below TN = 24 K, Mn2+ moments order ferromagnetically in the ab plane but antiferromagnetically along the crystallographic c axis. The ordered moment is 4.04(13)μB/Mn at 10 K and aligned along the crystallographic c axis in an A-type antiferromagnetic order. Below TN, the electrical resistivity drops upon cooling or when going across the metamagnetic transition in increasing magnetic fields ...


Thermodynamic Stabilities Of Perfect And Vacancy-Defected Li2 Tio3 (001) Surfaces From First-Principles Analyses, Yan Jiang, Yanli Shi, Xiaogang Xiang, Jianqi Qi, Yong Han, Zhijun Liao, Tiecheng Lu May 2019

Thermodynamic Stabilities Of Perfect And Vacancy-Defected Li2 Tio3 (001) Surfaces From First-Principles Analyses, Yan Jiang, Yanli Shi, Xiaogang Xiang, Jianqi Qi, Yong Han, Zhijun Liao, Tiecheng Lu

Ames Laboratory Accepted Manuscripts

Lithium titanate (Li2TiO3) is an attractive ceramic material for various industrial applications, particularly as one of the most promising breeder blanket materials in future nuclear-fusion reactors. Previously reported studies mainly focus on sintered polycrystalline samples of Li2TiO3. Surface structure of the single-crystal form is rarely reported, although the information of surface structures and stabilities can be critical for further understanding the surface-associated processes. In this work, we perform extensive first-principles density-functional-theory (DFT) calculations to obtain the surface energies of Li2TiO3 (001) with different surface terminations. For four perfect (defect-free) Li-, O-, or LiTi-terminated (001) surfaces, Li- or O-terminated (001) surfaces ...


Magnetic-Field Effects On The Fragile Antiferromagnetism In Ybbipt, Benjamin G. Ueland, Andreas Kreyssig, E. D. Mun, J. W. Lynn, L. W. Harriger, D. K. Pratt, K. Prokeš, Z. Hüsges, R. Toft-Petersen, S. Sauerbrei, Scott M. Saunders, Yuji Furukawa, Sergey L. Bud’Ko, Robert J. Mcqueeney, Paul C. Canfield, Alan I. Goldman May 2019

Magnetic-Field Effects On The Fragile Antiferromagnetism In Ybbipt, Benjamin G. Ueland, Andreas Kreyssig, E. D. Mun, J. W. Lynn, L. W. Harriger, D. K. Pratt, K. Prokeš, Z. Hüsges, R. Toft-Petersen, S. Sauerbrei, Scott M. Saunders, Yuji Furukawa, Sergey L. Bud’Ko, Robert J. Mcqueeney, Paul C. Canfield, Alan I. Goldman

Ames Laboratory Accepted Manuscripts

We present neutron-diffraction data for the cubic-heavy-fermion YbBiPt that show broad magnetic diffraction peaks due to the fragile short-range antiferromagnetic (AFM) order persist under an applied magnetic-field H. Our results for H perpendicular to[(1) over bar 1 0] and a temperature of T = 0.14(1) K show that the (1/2,1/2,3/2) magnetic diffraction peak can be described by the same two-peak line shape found for mu H-0 = 0T below the Neel temperature of T-N = 0.4 K. Both components of the peak exist for mu H-0 less than or similar to 1.4 T ...


Magnetocaloric Effect Of Gadolinium In High Magnetic Fields, T. Gottschall, M. D. Kuz’Min, K. P. Skokov, Y. Skourski, M. Fries, O. Gutfleisch, M. Ghorbani Zavareh, Deborah L. Schlagel, Yaroslav Mudryk, Vitalij K. Pecharsky, J. Wosnitza Apr 2019

Magnetocaloric Effect Of Gadolinium In High Magnetic Fields, T. Gottschall, M. D. Kuz’Min, K. P. Skokov, Y. Skourski, M. Fries, O. Gutfleisch, M. Ghorbani Zavareh, Deborah L. Schlagel, Yaroslav Mudryk, Vitalij K. Pecharsky, J. Wosnitza

Ames Laboratory Accepted Manuscripts

The magnetocaloric effect of gadolinium has been measured directly in pulsed magnetic fields up to 62 T. The maximum observed adiabatic temperature change is Delta T-ad = 60.5 K, the initial temperature T-0 being just above 300 K. The field dependence of Delta T-ad is found to follow the usual H-2/3 law, with a small correction in H-4/3. However, as H is increased, a radical change is observed in the dependence of Delta T-ad on T-0, at H = const. The familiar caret-shaped peak situated at T-0 = T-C becomes distinctly asymmetric, its high-temperature slope becoming more gentle and evolving ...


Anisotropy Induced Vortex Lattice Rearrangement In Cakfe4as4, Rustem Khasanov, William R. Meier, Sergey L. Bud’Ko, Hubertus Luetkens, Paul C. Canfield, Alex Amato Apr 2019

Anisotropy Induced Vortex Lattice Rearrangement In Cakfe4as4, Rustem Khasanov, William R. Meier, Sergey L. Bud’Ko, Hubertus Luetkens, Paul C. Canfield, Alex Amato

Ames Laboratory Accepted Manuscripts

The magnetic penetration depth anisotropy gamma(lambda) = lambda(c)/lambda(ab) (lambda(ab) and lambda(c) are the in-plane and the out-of-plane components of the magnetic penetration depth) in a CaKFe4As4 single crystal sample (the critical temperature T-c similar or equal to 35 K) was studied by means of muon-spin rotation (mu SR). gamma(lambda) is almost temperature independent for T less than or similar to 20 K (gamma(lambda) similar or equal to 1.9) and it reaches similar or equal to 3.0 by approaching T-c. The change of gamma(lambda) induces the corresponding rearrangement of the flux ...


Fragility Of Fermi Arcs In Dirac Semimetals, Yun Wu, Na Hyun Jo, Lin-Lin Wang, Connor A. Schmidt, Kathryn M. Neilson, Benjamin Schrunk, Przemyslaw Swatek, Andrew Eaton, Sergey L. Bud’Ko, Paul C. Canfield, Adam Kaminski Apr 2019

Fragility Of Fermi Arcs In Dirac Semimetals, Yun Wu, Na Hyun Jo, Lin-Lin Wang, Connor A. Schmidt, Kathryn M. Neilson, Benjamin Schrunk, Przemyslaw Swatek, Andrew Eaton, Sergey L. Bud’Ko, Paul C. Canfield, Adam Kaminski

Ames Laboratory Accepted Manuscripts

We use tunable, vacuum ultraviolet laser based angle-resolved photoemission spectroscopy and density functional theory (DFT) calculations to study the electronic properties of Dirac semimetal candidate cubic PtBi 2 . In addition to bulk electronic states we also find surface states in PtBi 2 , which is expected as PtBi 2 was theoretically predicated to be a candidate Dirac semimetal. The surface states are also well reproduced from DFT band calculations. Interestingly, the topological surface states form Fermi contours rather than double Fermi arcs that were observed in Na 3 Bi . The surface bands forming the Fermi contours merge with bulk bands in ...


Pressure-Temperature Phase Diagram Of The Eurbfe4as4 Superconductor, Li Xiang, Sergey L. Bud’Ko, Jin-Ke Bao, Duck Young Chung, Mercouri G. Kanatzidis, Paul C. Canfield Apr 2019

Pressure-Temperature Phase Diagram Of The Eurbfe4as4 Superconductor, Li Xiang, Sergey L. Bud’Ko, Jin-Ke Bao, Duck Young Chung, Mercouri G. Kanatzidis, Paul C. Canfield

Ames Laboratory Accepted Manuscripts

The pressure dependencies of the magnetic and superconducting transitions, as well as that of the superconducting upper critical field, are reported for single crystalline EuRbFe 4 As 4 . Resistance measurements were performed under hydrostatic pressures up to 6.21 GPa and in magnetic fields up to 9 T. Zero-field-cooled magnetization measurements were performed under hydrostatic pressures up to 1.24 GPa under 20 mT applied field. Superconducting transition temperature, T c , up to 6.21 GPa and magnetic transition temperature, T M , up to 1.24 GPa were obtained and a pressure-temperature phase diagram was constructed. Our results show that ...


Intelligent Metasurfaces With Continuously Tunable Local Surface Impedance For Multiple Reconfigurable Functions, Fu Liu, Odysseas Tsilipakos, Alexandros Pitilakis, Anna C. Tasolamprou, Mohammad Sajjad Mirmoosa, Nikolaos V. Kantartzis, Do-Hoon Kwon, Maria Kafesaki, Costas M. Soukoulis, Sergei A. Tretyakov Apr 2019

Intelligent Metasurfaces With Continuously Tunable Local Surface Impedance For Multiple Reconfigurable Functions, Fu Liu, Odysseas Tsilipakos, Alexandros Pitilakis, Anna C. Tasolamprou, Mohammad Sajjad Mirmoosa, Nikolaos V. Kantartzis, Do-Hoon Kwon, Maria Kafesaki, Costas M. Soukoulis, Sergei A. Tretyakov

Ames Laboratory Accepted Manuscripts

Electromagnetic metasurfaces can be characterized as intelligent if they are able to perform multiple tunable functions, with the desired response being controlled by a computer influencing the individual electromagnetic properties of each metasurface inclusion. In this paper, we present an example of an intelligent metasurface that operates in the reflection mode in the microwave frequency range. We numerically show that, without changing the main body of the metasurface, we can achieve tunable perfect absorption and tunable anomalous reflection. The tunability features can be implemented using mixed-signal integrated circuits (ICs), which can independently vary both the resistance and reactance, offering complete ...


Equation Of State Of Boron Nitride Combining Computation, Modeling, And Experiment, Shuai Zhang, Amy Lazicki, Burkhard Militzer, Lin H. Yang, Kyle Caspersen, Jim A. Gaffney, Markus W. Däne, John E. Pask, Walter R. Johnson, Abhiraj Sharma, Phanish Suryanarayana, Duane D. Johnson, Andrey V. Smirnov, Philip A. Sterne, David Erskine, Richard A. London, Federica Coppari, Damian Swift, Joseph Nilsen, Art J. Nelson, Heather D. Whitley Apr 2019

Equation Of State Of Boron Nitride Combining Computation, Modeling, And Experiment, Shuai Zhang, Amy Lazicki, Burkhard Militzer, Lin H. Yang, Kyle Caspersen, Jim A. Gaffney, Markus W. Däne, John E. Pask, Walter R. Johnson, Abhiraj Sharma, Phanish Suryanarayana, Duane D. Johnson, Andrey V. Smirnov, Philip A. Sterne, David Erskine, Richard A. London, Federica Coppari, Damian Swift, Joseph Nilsen, Art J. Nelson, Heather D. Whitley

Ames Laboratory Accepted Manuscripts

The equation of state (EOS) of materials at warm dense conditions poses significant challenges to both theory and experiment. We report a combined computational, modeling, and experimental investigation leveraging new theoretical and experimental capabilities to investigate warm-dense boron nitride (BN). The simulation methodologies include path integral Monte Carlo (PIMC), several density functional theory (DFT) molecular dynamics methods [plane-wave pseudopotential, Fermi operator expansion (FOE), and spectral quadrature (SQ)], activity expansion (actex), and all-electron Green's function Korringa-Kohn-Rostoker (mecca), and compute the pressure and internal energy of BN over a broad range of densities and temperatures. Our experiments were conducted at the ...


Rotationally Invariant Slave-Boson And Density Matrix Embedding Theory: Unified Framework And Comparative Study On The One-Dimensional And Two-Dimensional Hubbard Model, Tsung-Han Lee, Thomas Ayral, Yong-Xin Yao, Nicola Lanata, Gabriel Kotliar Mar 2019

Rotationally Invariant Slave-Boson And Density Matrix Embedding Theory: Unified Framework And Comparative Study On The One-Dimensional And Two-Dimensional Hubbard Model, Tsung-Han Lee, Thomas Ayral, Yong-Xin Yao, Nicola Lanata, Gabriel Kotliar

Ames Laboratory Accepted Manuscripts

We present detailed benchmark ground-state calculations of the one- and two-dimensional Hubbard model utilizing the cluster extensions of the rotationally invariant slave-boson mean-field theory and the density matrix embedding theory. Our analysis shows that the overall accuracy and the performance of these two methods are very similar. Furthermore, we propose a unified computational framework that allows us to implement both of these techniques on the same footing. This provides us with a different line of interpretation and paves the ways for developing systematically distinct generalizations of these complementary approaches.


Dzyaloshinskii-Moriya Interaction And The Magnetic Ground State In Magnetoelectric Licopo 4, Ellen Fogh, Oksana Zaharko, Jürg Schefer, Christof Niedermayer, Sonja Holm-Dahlin, Michael Korning Sørensen, Andreas Bott Kristensen, Niels Hessel Andersen, David Vaknin, Niels Bech Christensen, Rasmus Toft-Petersen Mar 2019

Dzyaloshinskii-Moriya Interaction And The Magnetic Ground State In Magnetoelectric Licopo 4, Ellen Fogh, Oksana Zaharko, Jürg Schefer, Christof Niedermayer, Sonja Holm-Dahlin, Michael Korning Sørensen, Andreas Bott Kristensen, Niels Hessel Andersen, David Vaknin, Niels Bech Christensen, Rasmus Toft-Petersen

Ames Laboratory Accepted Manuscripts

Magnetic structures are investigated by means of neutron diffraction to shine a light on the intricate details that are believed to be key to understanding the magnetoelectric effect in LiCoPO4. At zero field, a spontaneous spin canting of φ=7(1)∘ is found. The spins tilt away from the easy b-axis toward c. Symmetry considerations lead to the magnetic point group m′z, which is consistent with the previously observed magnetoelectric tensor form and weak ferromagnetic moment along b. For magnetic fields applied along a, the induced ferromagnetic moment couples via the Dzyaloshinskii-Moriya interaction to yield an additional field-induced spin ...


Mg Assisted Flux Growth And Characterization Of Single Crystalline Sm2co17, Tej Nath Lamichhane, Qisheng Lin, Valentin Taufour, Andriy Palasyuk, Tribhuwan Pandey, David Parker, Sergey L. Bud’Ko, Paul C. Canfield Mar 2019

Mg Assisted Flux Growth And Characterization Of Single Crystalline Sm2co17, Tej Nath Lamichhane, Qisheng Lin, Valentin Taufour, Andriy Palasyuk, Tribhuwan Pandey, David Parker, Sergey L. Bud’Ko, Paul C. Canfield

Ames Laboratory Accepted Manuscripts

This paper presents details of Mg-assisted flux growth of Sm2Co17 single crystals in a Ta crucible well below the melting temperature of binary Sm2Co17. Both the crushed single crystalline powder x-ray diffraction (XRD) and single crystalline XRD data revealed the Th2Zn17 type rhombohedral(R-3m) crystal structure. Ta atom is found to be statistically replacing the Co-Co dumbbell with its position being at the center of the dumbbell. The Curie temperature of our lightly Mg and Ta doped Sm2Co17 sample is determined to be ∼1100 K using method of generalized Bloch law fitting of easy axis spontaneous magnetization data.


Ultrafast Nonthermal Terahertz Electrodynamics And Possible Quantum Energy Transfer In The Nb3sn Superconductor, Xu Yang, X. Zhao, Chirag Vaswani, C. Sundahl, Boqun Song, Yong-Xin Yao, Di Cheng, Zhiyan Liu, Peter Orth, M. Mootz, J. H. Kang, I. E. Perakis, Cai-Zhuang Wang, Kai-Ming Ho, C. B. Eom, Jigang Wang Mar 2019

Ultrafast Nonthermal Terahertz Electrodynamics And Possible Quantum Energy Transfer In The Nb3sn Superconductor, Xu Yang, X. Zhao, Chirag Vaswani, C. Sundahl, Boqun Song, Yong-Xin Yao, Di Cheng, Zhiyan Liu, Peter Orth, M. Mootz, J. H. Kang, I. E. Perakis, Cai-Zhuang Wang, Kai-Ming Ho, C. B. Eom, Jigang Wang

Ames Laboratory Accepted Manuscripts

We report terahertz (THz) electrodynamics of a moderately clean A15 superconductor (SC) following ultrafast excitation to manipulate quasiparticle (QP) transport. In the Martensitic normal state, we observe a photo enhancement in the THz conductivity using optical pulses, while the opposite is observed for the THz pump. This demonstrates wavelength-selective nonthermal control of conductivity distinct from sample heating. The photo enhancement persists up to an additional critical temperature, above the SC one, from a competing electronic order. In the SC state, the fluence dependence of pair-breaking kinetics together with an analytic model provides an implication for a “one photon to one ...


Connection Between Mott Physics And Crystal Structure In A Series Of Transition Metal Binary Compounds, Nicola Lanatà, Tsung-Han Lee, Yong-Xin Yao, Vladan Stevanović, Vladimir Dobrosavljević Mar 2019

Connection Between Mott Physics And Crystal Structure In A Series Of Transition Metal Binary Compounds, Nicola Lanatà, Tsung-Han Lee, Yong-Xin Yao, Vladan Stevanović, Vladimir Dobrosavljević

Ames Laboratory Accepted Manuscripts

The choice that a solid system “makes” when adopting a crystal structure (stable or metastable) is ultimately governed by the interactions between electrons forming chemical bonds. Here we analyze six prototypical binary transition metal compounds and shed light on the connection between Mott physics and the behavior of the energy as a function of the spatial arrangement of the atoms in these systems. Remarkably, we find that the main qualitative features of this complex behavior in the Mott phase of these systems can be traced back to the fact that the strong d-electron correlations influence substantially the charge transfer ...


Crystal Growth, Microstructure, And Physical Properties Of Srmnsb2, Yong Liu, Tao Ma, Warren E. Straszheim, Farhan Islam, Brandt A. Jensen, Wei Tian, Thomas Heitmann, R. A. Rosenberg, John M. Wilde, Bing Li, Andreas Kreyssig, Alan I. Goldman, Benjamin G. Ueland, Robert J. Mcqueeney, David Vaknin Feb 2019

Crystal Growth, Microstructure, And Physical Properties Of Srmnsb2, Yong Liu, Tao Ma, Warren E. Straszheim, Farhan Islam, Brandt A. Jensen, Wei Tian, Thomas Heitmann, R. A. Rosenberg, John M. Wilde, Bing Li, Andreas Kreyssig, Alan I. Goldman, Benjamin G. Ueland, Robert J. Mcqueeney, David Vaknin

Ames Laboratory Accepted Manuscripts

We report on the crystal and magnetic structures and magnetic and transport properties of SrMnSb2 single crystals grown by the self-flux method. Magnetic susceptibility measurements reveal an antiferromagnetic (AFM) transition at TN=295(3) K. Above TN, the susceptibility slightly increases and forms a broad peak at T∼420 K, which is a typical feature of two-dimensional magnetic systems. Neutron diffraction measurements on single crystals confirm the previously reported C-type AFM structure below TN. Both de Haas-van Alphen (dHvA) and Shubnikov-de Haas (SdH) effects are observed in SrMnSb2 single crystals. Analysis of the oscillatory component by a Fourier transform shows ...


Nematicity In The Superconducting Mixed State Of Strain Detwinned Underdoped Ba(Fe1-Xcox)(2)As-2, J. Schmidt, V. Bekeris, G. S. Lozano, M. V. Bortulé, M. Marziali Bermúdez, C. W. Hicks, Paul C. Canfield, E. Fradkin, G. Pasquini Feb 2019

Nematicity In The Superconducting Mixed State Of Strain Detwinned Underdoped Ba(Fe1-Xcox)(2)As-2, J. Schmidt, V. Bekeris, G. S. Lozano, M. V. Bortulé, M. Marziali Bermúdez, C. W. Hicks, Paul C. Canfield, E. Fradkin, G. Pasquini

Ames Laboratory Accepted Manuscripts

Evidence of nematic effects in the mixed superconducting phase of slightly underdoped Ba(Fe1−xCox)2As2 is reported. We have found strong in-plane resistivity anisotropy for crystals in different strain conditions. For these compositions, there is no magnetic long-range order, so the description may be ascribed to the interplay between the superconducting and nematic order parameters. A piezoelectric-based apparatus is used to apply tensile or compressive strain to tune nematic domain orientation in order to examine intrinsic nematicity. Measurements are done under a rotating magnetic field, and the analysis of the angular dependence of physical quantities identifies the cases in ...


Competition Between Orthorhombic And Re-Entrant Tetragonal Phases In Underdoped Ba1-Xkxfe2as2 Probed By The Response To Controlled Disorder, Erik I. Timmons, Makariy A. Tanatar, K. Willa, S. Teknowijoyo, Kyuil Cho, M. Konczykowski, O. Cavani, Yong Liu, Thomas A. Lograsso, U. Welp, Ruslan Prozorov Feb 2019

Competition Between Orthorhombic And Re-Entrant Tetragonal Phases In Underdoped Ba1-Xkxfe2as2 Probed By The Response To Controlled Disorder, Erik I. Timmons, Makariy A. Tanatar, K. Willa, S. Teknowijoyo, Kyuil Cho, M. Konczykowski, O. Cavani, Yong Liu, Thomas A. Lograsso, U. Welp, Ruslan Prozorov

Ames Laboratory Accepted Manuscripts

Low-temperature (22 K) irradiation with 2.5-MeV electrons, creating point defects affecting elastic scattering, was used to study the competition between stripe C-2 and tetragonal C-4 antiferromagnetic phases which exist in a narrow doping range around x = 0.25 in hole-doped Ba1-xKxFe2As2. In nearby compositions outside of this range, at x = 0.22 and x = 0.19, the temperatures of both the concomitant orthorhombic/stripe antiferromagnetic transition T-C2 and the superconducting transition T-c are monotonically suppressed by added disorder at similar rates of about 0.1 K/mu Omega cm, as revealed through using resistivity variation as an intrinsic measure ...