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141 items found (0 items not approved), displaying 31 to 40.[First/Prev] 1, 2, 3, 4, 5, 6, 7, 8 [Next/Last]

Instruments / Technical Area	Publication Details	Published
	Absence of magnetic proximity effect at the interface of Bi2Se3 and (Bi,Sb)2Te3 with EuS A. I. Figueroa , F. Bonell , M. g. Cuxart , M. Valvidares , P. Gargiani , G. Van Der Laan , A. Mugarza , S. o. Valenzuela Physical Review Letters 125, 226801 DOI: 10.1103/PhysRevLett.125.226801 Show Abstract ▼ Abstract: We performed x-ray magnetic circular dichroism (XMCD) measurements on heterostructures comprising topological insulators (TIs) of the (Bi,Sb)2(Se,Te)3 family and the magnetic insulator EuS. XMCD measurements allow us to investigate element-selective magnetic proximity effects at the very TI/EuS interface. A systematic analysis reveals that there is neither significant induced magnetism within the TI nor an enhancement of the Eu magnetic moment at such interface. The induced magnetic moments in Bi, Sb, Te, and Se sites are lower than the estimated detection limit of the XMCD measurements of ∼10−3 μB/at.	Nov 2020
I09-Surface and Interface Structural Analysis	Surfactant-mediated epitaxial growth of single-layer graphene in an unconventional orientation on SiC F. C. Bocquet , Y.-R. Lin , M. Franke , N. Samiseresht , S. Parhizkar , S. Soubatch , T.-L. Lee , C. Kumpf , F. s. Tautz Physical Review Letters 125 DOI: 10.1103/PhysRevLett.125.106102 Diamond Proposal Number(s): [17737, 20810, 20855] Show Abstract ▼ Abstract: We report the use of a surfactant molecule during the epitaxy of graphene on SiC(0001) that leads to the growth in an unconventional orientation, namely R 0 ° rotation with respect to the SiC lattice. It yields a very high-quality single-layer graphene with a uniform orientation with respect to the substrate, on the wafer scale. We find an increased quality and homogeneity compared to the approach based on the use of a preoriented template to induce the unconventional orientation. Using spot profile analysis low-energy electron diffraction, angle-resolved photoelectron spectroscopy, and the normal incidence x-ray standing wave technique, we assess the crystalline quality and coverage of the graphene layer. Combined with the presence of a covalently bound graphene layer in the conventional orientation underneath, our surfactant-mediated growth offers an ideal platform to prepare epitaxial twisted bilayer graphene via intercalation.	Sep 2020
I10-Beamline for Advanced Dichroism - scattering	Depth-resolved magnetization dynamics revealed by X-ray reflectometry ferromagnetic resonance D. M. Burn , S. l. Zhang , G. q. Yu , Y. Guang , H. j. Chen , X. p. Qiu , Gerrit Van Der Laan , T. Hesjedal Physical Review Letters 125, 137201 DOI: 10.1103/PhysRevLett.125.137201 Diamond Proposal Number(s): [23895] Open Access Show Abstract ▼ Abstract: Magnetic multilayers offer diverse opportunities for the development of ultrafast functional devices through advanced interface and layer engineering. Nevertheless, a method for determining their dynamic properties as a function of depth throughout such stacks has remained elusive. By probing the ferromagnetic resonance modes with element-selective soft x-ray resonant reflectivity, we gain access to the magnetization dynamics as a function of depth. Most notably, using reflectometry ferromagnetic resonance, we find a phase lag between the coupled ferromagnetic layers in [CoFeB/MgO/Ta]4 multilayers that is invisible to other techniques. The use of reflectometry ferromagnetic resonance enables the time-resolved and depth-resolved probing of the complex magnetization dynamics of a wide range of functional magnetic heterostructures with absorption edges in the soft x-ray wavelength regime.	Sep 2020
I05-ARPES	Cubic rashba effect in the surface spin structure of rare-earth ternary materials D. y. Usachov , I. a. Nechaev , G. Poelchen , M. Guttler , E. e. Krasovskii , S. Schulz , A. Generalov , K. Kliemt , A. Kraiker , C. Krellner , K. Kummer , S. Danzenbächer , C. Laubschat , A. p. Weber , J. Sánchez-Barriga , E. v. Chulkov , A. f. Santander-Syro , T. Imai , K. Miyamoto , T. Okuda , D. V. Vyalikh Physical Review Letters 124 DOI: 10.1103/PhysRevLett.124.237202 Diamond Proposal Number(s): [18844, 17761] Show Abstract ▼ Abstract: Spin-orbit interaction and structure inversion asymmetry in combination with magnetic ordering is a promising route to novel materials with highly mobile spin-polarized carriers at the surface. Spin-resolved measurements of the photoemission current from the Si-terminated surface of the antiferromagnet TbRh 2 Si 2 and their analysis within an ab initio one-step theory unveil an unusual triple winding of the electron spin along the fourfold-symmetric constant energy contours of the surface states. A two-band k ⋅ p model is presented that yields the triple winding as a cubic Rashba effect. The curious in-plane spin-momentum locking is remarkably robust and remains intact across a paramagnetic-antiferromagnetic transition in spite of spin-orbit interaction on Rh atoms being considerably weaker than the out-of-plane exchange field due to the Tb 4 f moments.	Jun 2020
I21-Resonant Inelastic X-ray Scattering (RIXS)	High-temperature charge-stripe correlations in La1.675Eu0.2Sr0.125CuO4 Q. Wang , M. Horio , K. Von Arx , Y. Shen , D. John Mukkattukavil , Y. Sassa , O. Ivashko , C. E. Matt , S. Pyon , T. Takayama , H. Takagi , T. Kurosawa , N. Momono , M. Oda , T. Adachi , S. M. Haidar , Y. Koike , Y. Tseng , W. Zhang , J. Zhao , K. Kummer , M. Garcia-Fernandez , K. Zhou , N. B. Christensen , H. M. Ronnow , T. Schmitt , J. Chang Physical Review Letters 124 DOI: 10.1103/PhysRevLett.124.187002 Diamond Proposal Number(s): [20828, 24481] Show Abstract ▼ Abstract: We use resonant inelastic x-ray scattering to investigate charge-stripe correlations in La 1.675 Eu 0.2 Sr 0.125 CuO 4 . By differentiating elastic from inelastic scattering, it is demonstrated that charge-stripe correlations precede both the structural low-temperature tetragonal phase and the transport-defined pseudogap onset. The scattering peak amplitude from charge stripes decays approximately as T − 2 towards our detection limit. The in-plane integrated intensity, however, remains roughly temperature independent. Therefore, although the incommensurability shows a remarkably large increase at high temperature, our results are interpreted via a single scattering constituent. In fact, direct comparison to other stripe-ordered compounds ( La 1.875 Ba 0.125 CuO 4 , La 1.475 Nd 0.4 Sr 0.125 CuO 4 , and La 1.875 Sr 0.125 CuO 4 ) suggests a roughly constant integrated scattering intensity across all these compounds. Our results therefore provide a unifying picture for the charge-stripe ordering in La-based cuprates. As charge correlations in La 1.675 Eu 0.2 Sr 0.125 CuO 4 extend beyond the low-temperature tetragonal and pseudogap phase, their emergence heralds a spontaneous symmetry breaking in this compound.	May 2020
I09-Surface and Interface Structural Analysis	Simultaneous structural and electronic transitions in epitaxial VO2/TiO2(001) Galo J. Paez , Christopher N. Singh , Matthew J. Wahila , Keith E. Tirpak , Nicholas F. Quackenbush , Shawn Sallis , Hanjong Paik , Yufeng Liang , Darrell G. Schlom , Tien-Lin Lee , Christoph Schlueter , Wei-Cheng Lee , Louis F. J. Piper Physical Review Letters 124 DOI: 10.1103/PhysRevLett.124.196402 Diamond Proposal Number(s): [13812, 25355] Show Abstract ▼ Abstract: Recent reports have identified new metaphases of VO 2 with strain and/or doping, suggesting the structural phase transition and the metal-to-insulator transition might be decoupled. Using epitaxially strained VO 2 / Ti O 2 (001) thin films, which display a bulklike abrupt metal-to-insulator transition and rutile to monoclinic transition structural phase transition, we employ x-ray standing waves combined with hard x-ray photoelectron spectroscopy to simultaneously measure the structural and electronic transitions. This x-ray standing waves study elegantly demonstrates the structural and electronic transitions occur concurrently within experimental limits (±1K).	May 2020
I10-Beamline for Advanced Dichroism - scattering	Coherent transfer of spin angular momentum by evanescent spin waves within antiferromagnetic NiO Maciej Dabrowski , Takafumi Nakano , David Burn , Andreas Frisk , David G. Newman , Christoph Klewe , Qian Li , Mengmeng Yang , Padraic Shafer , Elke Arenholz , Thorsten Hesjedal , Gerrit Van Der Laan , Zi Q. Qiu , Robert J. Hicken Physical Review Letters 124, 217201 DOI: 10.1103/PhysRevLett.124.217201 Diamond Proposal Number(s): [17745, 19116, 20760] Show Abstract ▼ Abstract: Insulating antiferromagnets have recently emerged as efficient and robust conductors of spin current. Element-specific and phase-resolved x-ray ferromagnetic resonance has been used to probe the injection and transmission of ac spin current through thin epitaxial NiO(001) layers. The spin current is found to be mediated by coherent evanescent spin waves of GHz frequency, rather than propagating magnons of THz frequency, paving the way towards coherent control of the phase and amplitude of spin currents within an antiferromagnetic insulator at room temperature.	May 2020
I21-Resonant Inelastic X-ray Scattering (RIXS)	Strongly correlated charge density wave in La2-xSrxCuO4 evidenced by doping-dependent phonon anomaly J. Q. Lin , H. Miao , D. G. Mazzone , G. D. Gu , A. Nag , A. C. Walters , M. Garcia-Fernandez , A. Barbour , J. Pelliciari , I. Jarrige , M. Oda , K. Kurosawa , N. Momono , K. Zhou , V. Bisogni , X. Liu , M. P. M. Dean Physical Review Letters 124 DOI: 10.1103/PhysRevLett.124.207005 Diamond Proposal Number(s): [22261] Show Abstract ▼ Abstract: The discovery of charge-density-wave-related effects in the resonant inelastic x-ray scattering spectra of cuprates holds the tantalizing promise of clarifying the interactions that stabilize the electronic order. Here, we report a comprehensive resonant inelastic x-ray scattering study of La 2 − x Sr x CuO 4 finding that charge-density wave effects persist up to a remarkably high doping level of x = 0.21 before disappearing at x = 0.25 . The inelastic excitation spectra remain essentially unchanged with doping despite crossing a topological transition in the Fermi surface. This indicates that the spectra contain little or no direct coupling to electronic excitations near the Fermi surface, rather they are dominated by the resonant cross section for phonons and charge-density-wave-induced phonon softening. We interpret our results in terms of a charge-density wave that is generated by strong correlations and a phonon response that is driven by the charge-density-wave-induced modification of the lattice.	May 2020
I15-Extreme Conditions	Structural ordering in liquid gallium under extreme conditions James W. E. Drewitt , Francesco Turci , Benedict J. Heinen , Simon G. Macleod , Fei Qin , Annette K. Kleppe , Oliver T. Lord Physical Review Letters 124 DOI: 10.1103/PhysRevLett.124.145501 Diamond Proposal Number(s): [18961] Open Access Show Abstract ▼ Abstract: The atomic-scale structure, melting curve, and equation of state of liquid gallium has been measured to high pressure ( p ) and high temperature ( T ) up to 26 GPa and 900 K by in situ synchrotron x-ray diffraction. Ab initio molecular dynamics simulations up to 33.4 GPa and 1000 K are in excellent agreement with the experimental measurements, providing detailed insight at the level of pair distribution functions. The results reveal an absence of dimeric bonding in the liquid state and a continuous increase in average coordination number ¯ n Ga Ga from 10.4(2) at 0.1 GPa approaching ∼ 12 by 25 GPa. Topological cluster analysis of the simulation trajectories finds increasing fractions of fivefold symmetric and crystalline motifs at high p − T . Although the liquid progressively resembles a hard-sphere structure towards the melting curve, the deviation from this simple description remains large ( ≥ 40 % ) across all p − T space, with specific motifs of different geometries strongly correlating with low local two-body excess entropy at high p − T .	Apr 2020
I21-Resonant Inelastic X-ray Scattering (RIXS)	Many-body physics of single and double spin-flip excitations in NiO A. Nag , H. C. Robarts , F. Wenzel , J. Li , H. Elnaggar , R.-P. Wang , A. Walters , M. Garcia-Fernandez , F. M. F. De Groot , M. W. Haverkort , K. Zhou Physical Review Letters 124 DOI: 10.1103/PhysRevLett.124.067202 Open Access Show Abstract ▼ Abstract: Understanding many-body physics of elementary excitations has advanced our control over material properties. Here, we study spin-flip excitations in NiO using Ni L3-edge resonant inelastic x-ray scattering (RIXS) and present a strikingly different resonant energy behavior between single and double spin-flip excitations. Comparing our results with single-site full-multiplet ligand field theory calculations we find that the spectral weight of the double-magnon excitations originates primarily from the double spin-flip transition of the quadrupolar RIXS process within a single magnetic site. Quadrupolar spin-flip processes are among the least studied excitations, despite being important for multiferroic or spin-nematic materials due to their difficult detection. We identify intermediate state multiplets and intra-atomic core-valence exchange interactions as the key many-body factors determining the fate of such excitations. RIXS resonant energy dependence can act as a convincing proof of existence of nondipolar higher-ranked magnetic orders in systems for which, only theoretical predictions are available.	Feb 2020

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