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653 items found (0 items not approved), displaying 41 to 50.[First/Prev] 1, 2, 3, 4, 5, 6, 7, 8 [Next/Last]

Instruments / Technical Area	Publication Details	Published
I05-ARPES	Visualizing the out-of-plane electronic dispersions in an intercalated transition metal dichalcogenide Xian P. Yang , Harrison Labollita , Zi-Jia Cheng , Hari Bhandari , Tyler A. Cochran , Jia-Xin Yin , Md. Shafayat Hossain , Ilya Belopolski , Qi Zhang , Yuxiao Jiang , Nana Shumiya , Daniel Multer , Maksim Liskevich , Dmitry A. Usanov , Yanliu Dang , Vladimir N. Strocov , Albert V. Davydov , Nirmal J. Ghimire , Antia S. Botana , M. Zahid Hasan Physical Review B 105 DOI: 10.1103/PhysRevB.105.L121107 Diamond Proposal Number(s): [29230] Show Abstract ▼ Abstract: Layered transition metal dichalcogenides have a rich phase diagram and they feature two-dimensionality in numerous physical properties. Co 1 / 3 NbS 2 is one of the newest members of this family where Co atoms are intercalated into the van der Waals gaps between NbS 2 layers. We study the three-dimensional electronic band structure of Co 1 / 3 NbS 2 using both surface and bulk sensitive angle-resolved photoemission spectroscopy. We show that the electronic bands do not fit into the rigid band shift picture after the Co intercalation. Instead, Co 1 / 3 NbS 2 displays a different orbital character near the Fermi level compared to the pristine NbS 2 compound and has a clear band dispersion in the k z direction despite its layered structure. Our photoemission study demonstrates the out-of-plane electronic correlations introduced by the Co intercalation, thus offering a different perspective on this compound. Finally, we propose how Fermi level tuning could lead to exotic phases such as spin density wave instability.	Mar 2022
I11-High Resolution Powder Diffraction	Synthesis and structural, magnetic, electric, and thermoelectric characterization of layered Rh1−xIrxTe2 (0≤x≤1) Florencia E. Lurgo , Fernando Pomiro , Raúl E. Carbonio , Rodolfo D. Sánchez Physical Review B 105 DOI: 10.1103/PhysRevB.105.104104 Diamond Proposal Number(s): [18786] Show Abstract ▼ Abstract: Crystallographic analysis and thermoelectric studies of solid solutions Rh 1 − x Ir x Te 2 ( 0 ≤ x ≤ 1 ) are reported. All compositions show layered structures belonging to the P ¯ 3 m 1 space group at room temperature. IrTe 2 presents a first-order phase transition from the hexagonal to the triclinic lattice ( P ¯ 1 space group), which is monitored by synchrotron radiation x-ray powder diffraction. In the cooling-down process the transition appears at 240 K while in the warming-up process it begins at 280 K, showing a remarkable hysteresis. All compositions show a strong metallic behavior with enhanced Pauli paramagnetism and two regimes in the electrical resistivity. These regimes are associated with electron-electron scattering (at low temperature ρ ∼ T 2 ) and electron-phonon coupling (higher temperatures ρ ∼ T ). The Seebeck coefficient shows hole-type carriers for all the compounds.	Mar 2022
I11-High Resolution Powder Diffraction	Magnetic structure and exchange interactions in the Heisenberg pyrochlore antiferromagnet Gd2Pt2O7 Philip G. Welch , Joseph A. M. Paddison , Manh Duc Le , Jason S. Gardner , Wei-Tin Chen , Andrew R. Wildes , Andrew L. Goodwin , J. Ross Stewart Physical Review B 105 DOI: 10.1103/PhysRevB.105.094402 Show Abstract ▼ Abstract: The Heisenberg pyrochlore antiferromagnet Gd 2 Pt 2 O 7 is one of a series of gadolinium pyrochlore compounds with a variety of B-site cations. Despite the expected simplicity of a spin-only Gd 3 + Heisenberg interaction model, the gadolinium pyrochlore series exhibits various complex magnetic ground states at low temperature. Gd 2 Pt 2 O 7 displays the highest temperature magnetic order of the series with T N = 1.6 K, which has been attributed to enhanced superexchange pathways facilitated by empty 5 d e g Pt orbitals. In this study, we use various neutron scattering techniques on an isotopically enriched polycrystalline 160 Gd 2 Pt 2 O 7 sample to examine the magnetic structure and spin-wave excitation spectrum below T N in order to extract the dominant exchange interactions. We find that the ground-state magnetic structure is the Palmer-Chalker state previously seen in Gd 2 Sn 2 O 7 with an associated gapped excitation spectrum consistent with enhanced exchange interactions between further near-neighbor Gd 3 + ions. We confirm this exchange model with analysis of the magnetic diffuse scattering in the paramagnetic regime using polarized neutrons.	Mar 2022
	Hidden k-space magnetoelectric multipoles in nonmagnetic ferroelectrics Sayantika Bhowal , Stephen P. Collins , Nicola A. Spaldin Physical Review Letters 128 DOI: 10.1103/PhysRevLett.128.116402 Open Access Show Abstract ▼ Abstract: In condensed matter systems, the electronic degrees of freedom are often entangled to form complex composites, known as hidden orders, which give rise to unusual properties, while escaping detection in conventional experiments. Here we demonstrate the existence of hidden k -space magnetoelectric multipoles in nonmagnetic systems with broken space-inversion symmetry. These k -space magnetoelectric multipoles are reciprocal to the real-space charge dipoles associated with the broken inversion symmetry. Using the prototypical ferroelectric PbTiO 3 as an example, we show that their origin is a spin asymmetry in momentum space resulting from the broken space inversion symmetry associated with the ferroelectric polarization. In PbTiO 3 , the k -space spin asymmetry corresponds to a pure k -space magnetoelectric toroidal moment, which can be detected using magnetic Compton scattering, an established tool for probing magnetism in ferromagnets or ferrimagnets with a net spin polarization, which has not been exploited to date for nonmagnetic systems. In particular, the k -space magnetoelectric toroidal moment combined with the spin-orbit interaction manifest in an antisymmetric magnetic Compton profile that can be reversed using an electric field. Our work suggests an experimental route to directly measuring and tuning hidden k -space magnetoelectric multipoles via specially designed magnetic Compton scattering measurements.	Mar 2022
I15-Extreme Conditions	Synchrotron x-ray total scattering and modeling study of high-pressure-induced inhomogeneous atom reconfiguration in an equiatomic Zr50 Cu50 metallic glassy alloy Shifeng Luo , Jia Chuan Khong , Dominik Daisenberger , Shi Huang , Paul F. Mcmillan , Jiawei Mi Physical Review B 105 DOI: 10.1103/PhysRevB.105.064203 Diamond Proposal Number(s): [8858, 9902] Show Abstract ▼ Abstract: We studied in situ the local atomic structure evolution of an equiatomic Zr 50 Cu 50 metallic glassy alloy under high pressure compression inside a diamond anvil cell using synchrotron x-ray total scattering. The empirical potential structure refinement method was used to reconstruct the three-dimensional atomic models at each pressure step, and to analyze the spatially averaged local atomic structure configurations. The interatomic distances of different atomic pairs are reduced at different rates with increasing pressure and the Cu-Cu pairs exhibit the highest percentage reduction. Between ambient pressure and 36.85 GPa, the atomic separation of the Cu-Cu pairs is reduced by ∼12% compared to ∼5% for Zr-Zr and Zr-Cu pairs. Such disproportional decrease in interatomic distance results in inhomogeneous atom reconfiguration in the short atomic range. With the increase of pressure, the Zr atoms move preferentially towards the Zr-Zr pairs, while the Cu atoms move preferentially towards the Cu-Cu pairs, creating inhomogeneous atom reconfiguration with positive short-range order coefficients of 0.0309 and 0.0464 for Zr-Zr and Cu-Cu respectively, but a negative value of −0.0464 for Zr-Cu pairs. Voronoi tessellation method was also used to study the evolution of the short-range atom packing versus pressure, elucidating the cause for the bimodal distribution of the bond angle distributions. The research sheds light on understanding of the atomic reconfiguration of equiatomic alloys under high pressure.	Feb 2022
I09-Surface and Interface Structural Analysis	Correlation-induced emergent charge order in metallic vanadium dioxide Christopher N. Singh , Louis F. J. Piper , Hanjong Paik , Darrell G. Schlom , Wei-Cheng Lee Physical Review B 105 DOI: 10.1103/PhysRevB.105.035150 Diamond Proposal Number(s): [25355, 13812] Show Abstract ▼ Abstract: Recent progress in the growth and characterization of thin-film VO 2 has shown its electronic properties can be significantly modulated by epitaxial matching. To throw new light on the concept of “Mott engineering,” we develop a symmetry-consistent approach to treat structural distortions and electronic correlations in epitaxial VO 2 films under strain, and compare our design with direct experimental probes. We find strong evidence for the emergence of correlation-driven charge order deep in the metallic phase, and our results indicate that exotic phases of VO 2 can be controlled with epitaxial stabilization.	Jan 2022
I09-Surface and Interface Structural Analysis	Lifetime effects and satellites in the photoelectron spectrum of tungsten metal C. Kalha , L. E. Ratcliff , J. J. Gutiérrez Moreno , S. Mohr , M. Mantsinen , N. K. Fernando , P. K. Thakur , T.-L. Lee , H.-H. Tseng , T. S. Nunney , J. M. Kahk , J. Lischner , A. Regoutz Physical Review B 105 DOI: 10.1103/PhysRevB.105.045129 Diamond Proposal Number(s): [27164] Show Abstract ▼ Abstract: Tungsten (W) is an important and versatile transition metal and has a firm place at the heart of many technologies. A popular experimental technique for the characterization of tungsten and tungsten-based compounds is x-ray photoelectron spectroscopy (XPS), which enables the assessment of chemical states and electronic structure through the collection of core level and valence band spectra. However, in the case of tungsten metal, open questions remain regarding the origin, nature, and position of satellite features that are prominent in the photoelectron spectrum. These satellites are a fingerprint of the electronic structure of the material and have not been thoroughly investigated, at times leading to their misinterpretation. The present work combines high-resolution soft and hard x-ray photoelectron spectroscopy (SXPS and HAXPES) with reflected electron energy loss spectroscopy (REELS) and a multitiered ab initio theoretical approach, including density functional theory (DFT) and many-body perturbation theory (G0W0 and GW + C ), to disentangle the complex set of experimentally observed satellite features attributed to the generation of plasmons and interband transitions. This combined experiment-theory strategy is able to uncover previously undocumented satellite features, improving our understanding of their direct relationship to tungsten's electronic structure. Furthermore, it lays the groundwork for future studies into tungsten-based mixed-metal systems and holds promise for the reassessment of the photoelectron spectra of other transition and post-transition metals, where similar questions regarding satellite features remain.	Jan 2022
Theoretical Physics	Magnetic properties of RuO2 and charge-magnetic interference in Bragg diffraction of circularly polarized x-rays S. W. Lovesey , D. D. Khalyavin , G. Van Der Laan Physical Review B 105, 014403 DOI: 10.1103/PhysRevB.105.014403 Show Abstract ▼ Abstract: Rutile-type RuO2 likely supports a simple antiferromagnetic structure which can be verified by x-ray Bragg diffraction. Three magnetic motifs that do not break translation symmetry are explored in calculations of amplitudes suitable for diffraction enhanced by tuning the primary x-ray energy to a ruthenium atomic resonance. Coupling to x-ray helicity through a charge-magnetic interference is common to all motifs, together with magnetic and charge intensities in quadrature in the rotated channel of polarization. Necessary conditions for these diffraction phenomena are a centrosymmetric crystal structure, null magnetic propagation vector, and absence of a linear magnetoelectric effect. Published x-ray diffraction data for RuO2 were analyzed by the authors against a magnetic motif that does not satisfy the conditions. A polarized neutron study of antiferromagnetic domains can be achieved with a sample that meets the stated crystal and magnetic symmetries.	Jan 2022
I09-Surface and Interface Structural Analysis	Mapping hidden space-charge distributions across crystalline metal oxide/group IV semiconductor interfaces S. A. Chambers , M. Chrysler , J. H. Ngai , T.-L. Lee , J. Gabel , B. E. Matthews , S. R. Spurgeon , M. E. Bowden , Z. Zhu , P. V. Sushko Physical Review Materials 6 DOI: 10.1103/PhysRevMaterials.6.015002 Diamond Proposal Number(s): [25582] Show Abstract ▼ Abstract: The electronic structures of semiconducting heterojunctions are critically dependent on composition including the presence and concentrations of dopants, both intended and unintended. Dopant profiles in the interfacial region can have major effects on band energies which in turn drive transport properties. Here we use core-level photoelectron line shapes excited with hard x rays to extract information about electric fields resulting from internal charge transfer in epitaxial La 0.03 Sr 0.97 Zr x Ti 1 – x O 3 / Ge ( 001 ) ( 0.1 ≤ x ≤ 0.7 ) heterostructures. Experiments were carried out for heterojunctions involving both n - and p -type Ge substrates. These heterojunctions were not amenable to electronic characterization of all regions by transport measurements because the doped substrates act as electrical shunts, precluding probing the more resistive films and masking interface conductivity. However, the core-level line shapes were found to be a rich source of information on built-in potentials that exist throughout the heterostructure, and yielded valuable insight into the impact of band bending on band alignment at the buried interfaces. The electronic effects expected for Ge with uniform n - and p -type doping are eclipsed by those of unintended oxygen dopants in the Ge near the interface. This study illustrates the power of hard x-ray photoemission spectroscopy and related modeling to determine electronic structure in material systems for which insight from traditional transport measurements is limited.	Jan 2022
I05-ARPES	Coupling to zone-center optical phonons in VSe2 enhanced by charge density waves Y. Falke , N. Ehlen , G. Marini , A. V. Fedorov , V. Y. Voroshnin , B. V. Senkovskiy , K. Nikonov , M. Hoesch , T. K. Kim , L. Petaccia , G. Di Santo , T. Szkopek , G. Profeta , A. Gruneis Physical Review B 104 DOI: 10.1103/PhysRevB.104.235137 Diamond Proposal Number(s): [17064] Show Abstract ▼ Abstract: We investigate electron-phonon coupling (EPC) in the charge density wave (CDW) phase of V Se 2 by Raman spectroscopy, angle-resolved photoemission spectroscopy (ARPES), and ab initio calculations. Zone folding induced by the 4 × 4 in-plane CDW phase promotes the appearance of a Raman peak at ∼ 170 cm − 1 . The suppression of ARPES intensity in parts of the Fermi surface is also a result of CDW-induced zone folding and anticrossing of the electron energy bands. The appearance of the new Raman peak is in line with the ARPES observation of a kink feature in the spectral function at the same energy. A self-energy analysis yields an EPC constant of λ = 0.3 . Our calculations of the EPC are in excellent agreement and reveal that the kink is caused by several optical phonon branches close in energy. Our paper highlights the CDW phase as a means of inducing EPC pathways to optical phonons that directly affect its Raman spectrum.	Dec 2021

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