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Laguta VV, Kamba S, Maryško M, Andrzejewski B, Kachlík M, Maca K, Lee JH, Schlom DG. Magnetic resonance study of bulk and thin film EuTiO 3. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:105401. [PMID: 28075333 DOI: 10.1088/1361-648x/aa58c6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Magnetic resonance spectra of EuTiO3 in both bulk and thin film form were taken at temperatures from 3-350 K and microwave frequencies from 9.2-9.8 and 34 GHz. In the paramagnetic phase, magnetic resonance spectra are determined by magnetic dipole and exchange interactions between Eu2+ spins. In the film, a large contribution arises from the demagnetization field. From detailed analysis of the linewidth and its temperature dependence, the parameters of spin-spin interactions were determined: the exchange frequency is 10.5 GHz and the estimated critical exponent of the spin correlation length is ≈0.4. In the bulk samples, the spectra exhibited a distinct minimum in the linewidth at the Néel temperature, T N ≈ 5.5 K, while the resonance field practically does not change even on cooling below T N. This is indicative of a small magnetic anisotropy ~320 G in the antiferromagnetic phase. In the film, the magnetic resonance spectrum is split below T N into several components due to excitation of the magnetostatic modes, corresponding to a non-uniform precession of magnetization. Moreover, the film was observed to degrade over two years. This was manifested by an increase of defects and a change in the domain structure. The saturated magnetization in the film, estimated from the magnetic resonance spectrum, was about 900 emu cm-3 or 5.5 µ B/unit cell at T = 3.5 K.
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Kuo DY, Kawasaki JK, Nelson JN, Kloppenburg J, Hautier G, Shen KM, Schlom DG, Suntivich J. Influence of Surface Adsorption on the Oxygen Evolution Reaction on IrO2(110). J Am Chem Soc 2017; 139:3473-3479. [DOI: 10.1021/jacs.6b11932] [Citation(s) in RCA: 216] [Impact Index Per Article: 30.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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78
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Wei HI, Adamo C, Nowadnick EA, Lochocki EB, Chatterjee S, Ruf JP, Beasley MR, Schlom DG, Shen KM. Electron Doping of the Parent Cuprate La_{2}CuO_{4} without Cation Substitution. PHYSICAL REVIEW LETTERS 2016; 117:147002. [PMID: 27740780 DOI: 10.1103/physrevlett.117.147002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Indexed: 06/06/2023]
Abstract
In the cuprates, carrier doping of the Mott insulating parent state is necessary to realize superconductivity as well as a number of other exotic states involving charge or spin density waves. Cation substitution is the primary method for doping carriers into these compounds, and is the only known method for electron doping in these materials. Here, we report electron doping without cation substitution in epitaxially stabilized thin films of La_{2}CuO_{4} grown via molecular-beam epitaxy. We use angle-resolved photoemission spectroscopy to directly measure their electronic structure and conclusively determine that these compounds are electron doped with a carrier concentration of 0.09±0.02 e^{-}/Cu. We propose that intrinsic defects, most likely oxygen vacancies, are the sources of doped electrons in these materials. Our results suggest a new approach to electron doping in the cuprates, one which could lead to a more detailed experimental understanding of their properties.
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Mundy JA, Brooks CM, Holtz ME, Moyer JA, Das H, Rébola AF, Heron JT, Clarkson JD, Disseler SM, Liu Z, Farhan A, Held R, Hovden R, Padgett E, Mao Q, Paik H, Misra R, Kourkoutis LF, Arenholz E, Scholl A, Borchers JA, Ratcliff WD, Ramesh R, Fennie CJ, Schiffer P, Muller DA, Schlom DG. Atomically engineered ferroic layers yield a room-temperature magnetoelectric multiferroic. Nature 2016; 537:523-7. [DOI: 10.1038/nature19343] [Citation(s) in RCA: 240] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Accepted: 07/25/2016] [Indexed: 11/09/2022]
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80
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Li L, Britson J, Jokisaari JR, Zhang Y, Adamo C, Melville A, Schlom DG, Chen LQ, Pan X. Giant Resistive Switching via Control of Ferroelectric Charged Domain Walls. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2016; 28:6574-6580. [PMID: 27213756 DOI: 10.1002/adma.201600160] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Revised: 04/02/2016] [Indexed: 06/05/2023]
Abstract
Controlled switching of resistivity in ferroelectric thin films is demonstrated by writing and erasing stable, nanoscale, strongly charged domain walls using an in situ transmission electron microscopy technique. The resistance can be read nondestructively and presents the largest off/on ratio (≈10(5) ) ever reported in room-temperature ferroelectric devices, opening new avenues for engineering ferroelectric thin-film devices.
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81
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Plaza M, Huang X, Ko JYP, Shen M, Simpson BH, Rodríguez-López J, Ritzert NL, Letchworth-Weaver K, Gunceler D, Schlom DG, Arias TA, Brock JD, Abruña HD. Structure of the Photo-catalytically Active Surface of SrTiO3. J Am Chem Soc 2016; 138:7816-9. [DOI: 10.1021/jacs.6b03338] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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82
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Li D, Sharma AA, Gala DK, Shukla N, Paik H, Datta S, Schlom DG, Bain JA, Skowronski M. Joule Heating-Induced Metal-Insulator Transition in Epitaxial VO2/TiO2 Devices. ACS APPLIED MATERIALS & INTERFACES 2016; 8:12908-12914. [PMID: 27136956 DOI: 10.1021/acsami.6b03501] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
DC and pulse voltage-induced metal-insulator transition (MIT) in epitaxial VO2 two terminal devices were measured at various stage temperatures. The power needed to switch the device to the ON-state decrease linearly with increasing stage temperature, which can be explained by the Joule heating effect. During transient voltage induced MIT measurement, the incubation time varied across 6 orders of magnitude. Both DC I-V characteristic and incubation times calculated from the electrothermal simulations show good agreement with measured values, indicating Joule heating effect is the cause of MIT with no evidence of electronic effects. The width of the metallic filament in the ON-state of the device was extracted and simulated within the thermal model.
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83
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Burganov B, Adamo C, Mulder A, Uchida M, King PDC, Harter JW, Shai DE, Gibbs AS, Mackenzie AP, Uecker R, Bruetzam M, Beasley MR, Fennie CJ, Schlom DG, Shen KM. Strain Control of Fermiology and Many-Body Interactions in Two-Dimensional Ruthenates. PHYSICAL REVIEW LETTERS 2016; 116:197003. [PMID: 27232037 DOI: 10.1103/physrevlett.116.197003] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Indexed: 06/05/2023]
Abstract
Here we demonstrate how the Fermi surface topology and quantum many-body interactions can be manipulated via epitaxial strain in the spin-triplet superconductor Sr_{2}RuO_{4} and its isoelectronic counterpart Ba_{2}RuO_{4} using oxide molecular beam epitaxy, in situ angle-resolved photoemission spectroscopy, and transport measurements. Near the topological transition of the γ Fermi surface sheet, we observe clear signatures of critical fluctuations, while the quasiparticle mass enhancement is found to increase rapidly and monotonically with increasing Ru-O bond distance. Our work demonstrates the possibilities for using epitaxial strain as a disorder-free means of manipulating emergent properties, many-body interactions, and potentially the superconductivity in correlated materials.
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84
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Bhaskar UK, Banerjee N, Abdollahi A, Wang Z, Schlom DG, Rijnders G, Catalan G. A flexoelectric microelectromechanical system on silicon. NATURE NANOTECHNOLOGY 2016; 11:263-266. [PMID: 26571008 DOI: 10.1038/nnano.2015.260] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Accepted: 10/07/2015] [Indexed: 06/05/2023]
Abstract
Flexoelectricity allows a dielectric material to polarize in response to a mechanical bending moment and, conversely, to bend in response to an electric field. Compared with piezoelectricity, flexoelectricity is a weak effect of little practical significance in bulk materials. However, the roles can be reversed at the nanoscale. Here, we demonstrate that flexoelectricity is a viable route to lead-free microelectromechanical and nanoelectromechanical systems. Specifically, we have fabricated a silicon-compatible thin-film cantilever actuator with a single flexoelectrically active layer of strontium titanate with a figure of merit (curvature divided by electric field) of 3.33 MV(-1), comparable to that of state-of-the-art piezoelectric bimorph cantilevers.
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85
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Tate MW, Purohit P, Chamberlain D, Nguyen KX, Hovden R, Chang CS, Deb P, Turgut E, Heron JT, Schlom DG, Ralph DC, Fuchs GD, Shanks KS, Philipp HT, Muller DA, Gruner SM. High Dynamic Range Pixel Array Detector for Scanning Transmission Electron Microscopy. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2016; 22:237-49. [PMID: 26750260 DOI: 10.1017/s1431927615015664] [Citation(s) in RCA: 173] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
We describe a hybrid pixel array detector (electron microscope pixel array detector, or EMPAD) adapted for use in electron microscope applications, especially as a universal detector for scanning transmission electron microscopy. The 128×128 pixel detector consists of a 500 µm thick silicon diode array bump-bonded pixel-by-pixel to an application-specific integrated circuit. The in-pixel circuitry provides a 1,000,000:1 dynamic range within a single frame, allowing the direct electron beam to be imaged while still maintaining single electron sensitivity. A 1.1 kHz framing rate enables rapid data collection and minimizes sample drift distortions while scanning. By capturing the entire unsaturated diffraction pattern in scanning mode, one can simultaneously capture bright field, dark field, and phase contrast information, as well as being able to analyze the full scattering distribution, allowing true center of mass imaging. The scattering is recorded on an absolute scale, so that information such as local sample thickness can be directly determined. This paper describes the detector architecture, data acquisition system, and preliminary results from experiments with 80-200 keV electron beams.
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86
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Lebens-Higgins Z, Scanlon DO, Paik H, Sallis S, Nie Y, Uchida M, Quackenbush NF, Wahila MJ, Sterbinsky GE, Arena DA, Woicik JC, Schlom DG, Piper LFJ. Direct Observation of Electrostatically Driven Band Gap Renormalization in a Degenerate Perovskite Transparent Conducting Oxide. PHYSICAL REVIEW LETTERS 2016; 116:027602. [PMID: 26824566 DOI: 10.1103/physrevlett.116.027602] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Indexed: 05/28/2023]
Abstract
We have directly measured the band gap renormalization associated with the Moss-Burstein shift in the perovskite transparent conducting oxide (TCO), La-doped BaSnO_{3}, using hard x-ray photoelectron spectroscopy. We determine that the band gap renormalization is almost entirely associated with the evolution of the conduction band. Our experimental results are supported by hybrid density functional theory supercell calculations. We determine that unlike conventional TCOs where interactions with the dopant orbitals are important, the band gap renormalization in La-BaSnO_{3} is driven purely by electrostatic interactions.
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87
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Schlom DG, Fennie CJ. Ferroelectrics: The positives of going negative. NATURE MATERIALS 2015; 14:969-970. [PMID: 26259105 DOI: 10.1038/nmat4391] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
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88
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Nie YF, Di Sante D, Chatterjee S, King PDC, Uchida M, Ciuchi S, Schlom DG, Shen KM. Formation and Observation of a Quasi-Two-Dimensional dxy Electron Liquid in Epitaxially Stabilized Sr(2-x)La(x)TiO4 Thin Films. PHYSICAL REVIEW LETTERS 2015; 115:096405. [PMID: 26371669 DOI: 10.1103/physrevlett.115.096405] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Indexed: 06/05/2023]
Abstract
We report the formation and observation of an electron liquid in Sr(2-x)La(x)TiO4, the quasi-two-dimensional counterpart of SrTiO3, through reactive molecular-beam epitaxy and in situ angle-resolved photoemission spectroscopy. The lowest lying states are found to be comprised of Ti 3d_{xy} orbitals, analogous to the LaAlO3/SrTiO3 interface and exhibit unusually broad features characterized by quantized energy levels and a reduced Luttinger volume. Using model calculations, we explain these characteristics through an interplay of disorder and electron-phonon coupling acting cooperatively at similar energy scales, which provides a possible mechanism for explaining the low free carrier concentrations observed at various oxide heterostructures such as the LaAlO3/SrTiO3 interface.
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89
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Quackenbush NF, Paik H, Woicik JC, Arena DA, Schlom DG, Piper LFJ. X-Ray Spectroscopy of Ultra-Thin Oxide/Oxide Heteroepitaxial Films: A Case Study of Single-Nanometer VO2/TiO2. MATERIALS 2015; 8:5452-5466. [PMID: 28793516 PMCID: PMC5455529 DOI: 10.3390/ma8085255] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Revised: 08/12/2015] [Accepted: 08/14/2015] [Indexed: 11/23/2022]
Abstract
Epitaxial ultra-thin oxide films can support large percent level strains well beyond their bulk counterparts, thereby enabling strain-engineering in oxides that can tailor various phenomena. At these reduced dimensions (typically < 10 nm), contributions from the substrate can dwarf the signal from the epilayer, making it difficult to distinguish the properties of the epilayer from the bulk. This is especially true for oxide on oxide systems. Here, we have employed a combination of hard X-ray photoelectron spectroscopy (HAXPES) and angular soft X-ray absorption spectroscopy (XAS) to study epitaxial VO2/TiO2 (100) films ranging from 7.5 to 1 nm. We observe a low-temperature (300 K) insulating phase with evidence of vanadium-vanadium (V-V) dimers and a high-temperature (400 K) metallic phase absent of V-V dimers irrespective of film thickness. Our results confirm that the metal insulator transition can exist at atomic dimensions and that biaxial strain can still be used to control the temperature of its transition when the interfaces are atomically sharp. More generally, our case study highlights the benefits of using non-destructive XAS and HAXPES to extract out information regarding the interfacial quality of the epilayers and spectroscopic signatures associated with exotic phenomena at these dimensions.
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90
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Park J, Zhang Q, Chen P, Cosgriff MP, Tilka JA, Adamo C, Schlom DG, Wen H, Zhu Y, Evans PG. Spatially confined low-power optically pumped ultrafast synchrotron x-ray nanodiffraction. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2015; 86:083904. [PMID: 26329208 DOI: 10.1063/1.4929436] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The combination of ultrafast optical excitation and time-resolved synchrotron x-ray nanodiffraction provides unique insight into the photoinduced dynamics of materials, with the spatial resolution required to probe individual nanostructures or small volumes within heterogeneous materials. Optically excited x-ray nanobeam experiments are challenging because the high total optical power required for experimentally relevant optical fluences leads to mechanical instability due to heating. For a given fluence, tightly focusing the optical excitation reduces the average optical power by more than three orders of magnitude and thus ensures sufficient thermal stability for x-ray nanobeam studies. Delivering optical pulses via a scannable fiber-coupled optical objective provides a well-defined excitation geometry during rotation and translation of the sample and allows the selective excitation of isolated areas within the sample. Experimental studies of the photoinduced lattice dynamics of a 35 nm BiFeO3 thin film on a SrTiO3 substrate demonstrate the potential to excite and probe nanoscale volumes.
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91
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Disseler SM, Borchers JA, Brooks CM, Mundy JA, Moyer JA, Hillsberry DA, Thies EL, Tenne DA, Heron J, Holtz ME, Clarkson JD, Stiehl GM, Schiffer P, Muller DA, Schlom DG, Ratcliff WD. Magnetic structure and ordering of multiferroic hexagonal LuFeO_{3}. PHYSICAL REVIEW LETTERS 2015; 114:217602. [PMID: 26066458 DOI: 10.1103/physrevlett.114.217602] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Indexed: 06/04/2023]
Abstract
We report on the magnetic structure and ordering of hexagonal LuFeO_{3} films of variable thickness grown by molecular-beam epitaxy on YSZ (111) and Al_{2}O_{3} (0001) substrates. These crystalline films exhibit long-range structural uniformity dominated by the polar P6_{3}cm phase, which is responsible for the paraelectric to ferroelectric transition that occurs above 1000 K. Using bulk magnetometry and neutron diffraction, we find that the system orders into a ferromagnetically canted antiferromagnetic state via a single transition below 155 K regardless of film thickness, which is substantially lower than that previously reported in hexagonal LuFeO_{3} films. The symmetry of the magnetic structure in the ferroelectric state implies that this material is a strong candidate for linear magnetoelectric coupling and control of the ferromagnetic moment directly by an electric field.
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92
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Bischak CG, Hetherington CL, Wang Z, Precht JT, Kaz DM, Schlom DG, Ginsberg NS. Cathodoluminescence-activated nanoimaging: noninvasive near-field optical microscopy in an electron microscope. NANO LETTERS 2015; 15:3383-3390. [PMID: 25855869 DOI: 10.1021/acs.nanolett.5b00716] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We demonstrate a new nanoimaging platform in which optical excitations generated by a low-energy electron beam in an ultrathin scintillator are used as a noninvasive, near-field optical scanning probe of an underlying sample. We obtain optical images of Al nanostructures with 46 nm resolution and validate the noninvasiveness of this approach by imaging a conjugated polymer film otherwise incompatible with electron microscopy due to electron-induced damage. The high resolution, speed, and noninvasiveness of this "cathodoluminescence-activated" platform also show promise for super-resolution bioimaging.
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93
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Nie YF, King PDC, Kim CH, Uchida M, Wei HI, Faeth BD, Ruf JP, Ruff JPC, Xie L, Pan X, Fennie CJ, Schlom DG, Shen KM. Interplay of spin-orbit interactions, dimensionality, and octahedral rotations in semimetallic SrIrO(3). PHYSICAL REVIEW LETTERS 2015; 114:016401. [PMID: 25615483 DOI: 10.1103/physrevlett.114.016401] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Indexed: 06/04/2023]
Abstract
We employ reactive molecular-beam epitaxy to synthesize the metastable perovskite SrIrO(3) and utilize in situ angle-resolved photoemission to reveal its electronic structure as an exotic narrow-band semimetal. We discover remarkably narrow bands which originate from a confluence of strong spin-orbit interactions, dimensionality, and both in- and out-of-plane IrO(6) octahedral rotations. The partial occupation of numerous bands with strongly mixed orbital characters signals the breakdown of the single-band Mott picture that characterizes its insulating two-dimensional counterpart, Sr(2)IrO(4), illustrating the power of structure-property relations for manipulating the subtle balance between spin-orbit interactions and electron-electron interactions.
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94
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Bischak CG, Hetherington CL, Precht JT, Stachelrodt CE, Wang Z, Schlom DG, Ginsberg NS. Super Resolution Fluorescence Microscopy by Cathodoluminescence-Activated Excitation. Biophys J 2015. [DOI: 10.1016/j.bpj.2014.11.223] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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95
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Hetherington CL, Bischak CG, Stachelrodt CE, Precht JT, Wang Z, Schlom DG, Ginsberg NS. Superresolution Fluorescence Microscopy within a Scanning Electron Microscope. Biophys J 2015. [DOI: 10.1016/j.bpj.2014.11.1054] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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96
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Huefner M, Ghosh RK, Freeman E, Shukla N, Paik H, Schlom DG, Datta S. Hubbard gap modulation in vanadium dioxide nanoscale tunnel junctions. NANO LETTERS 2014; 14:6115-6120. [PMID: 25268467 DOI: 10.1021/nl502065b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We locally investigate the electronic transport through individual tunnel junctions containing a 10 nm thin film of vanadium dioxide (VO2) across its thermally induced phase transition. The insulator-to-metal phase transition in the VO2 film collapses the Hubbard gap (experimentally determined to be 0.4 ± 0.07 V), leading to several orders of magnitude change in tunnel conductance. We quantitatively evaluate underlying transport mechanisms via theoretical quantum mechanical transport calculations which show excellent agreement with the experimental results.
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97
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King PDC, Wei HI, Nie YF, Uchida M, Adamo C, Zhu S, He X, Božović I, Schlom DG, Shen KM. Atomic-scale control of competing electronic phases in ultrathin LaNiO₃. NATURE NANOTECHNOLOGY 2014; 9:443-7. [PMID: 24705511 DOI: 10.1038/nnano.2014.59] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2013] [Accepted: 02/21/2014] [Indexed: 05/27/2023]
Abstract
In an effort to scale down electronic devices to atomic dimensions, the use of transition-metal oxides may provide advantages over conventional semiconductors. Their high carrier densities and short electronic length scales are desirable for miniaturization, while strong interactions that mediate exotic phase diagrams open new avenues for engineering emergent properties. Nevertheless, understanding how their correlated electronic states can be manipulated at the nanoscale remains challenging. Here, we use angle-resolved photoemission spectroscopy to uncover an abrupt destruction of Fermi liquid-like quasiparticles in the correlated metal LaNiO₃ when confined to a critical film thickness of two unit cells. This is accompanied by the onset of an insulating phase as measured by electrical transport. We show how this is driven by an instability to an incipient order of the underlying quantum many-body system, demonstrating the power of artificial confinement to harness control over competing phases in complex oxides with atomic-scale precision.
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98
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Shukla N, Parihar A, Freeman E, Paik H, Stone G, Narayanan V, Wen H, Cai Z, Gopalan V, Engel-Herbert R, Schlom DG, Raychowdhury A, Datta S. Synchronized charge oscillations in correlated electron systems. Sci Rep 2014. [PMCID: PMC4019945 DOI: 10.1038/srep04964] [Citation(s) in RCA: 112] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Strongly correlated phases exhibit collective carrier dynamics that if properly harnessed can enable novel functionalities and applications. In this article, we investigate the phenomenon of electrical oscillations in a prototypical MIT system, vanadium dioxide (VO2). We show that the key to such oscillatory behaviour is the ability to induce and stabilize a non-hysteretic and spontaneously reversible phase transition using a negative feedback mechanism. Further, we investigate the synchronization and coupling dynamics of such VO2 based relaxation oscillators and show, via experiment and simulation, that this coupled oscillator system exhibits rich non-linear dynamics including charge oscillations that are synchronized in both frequency and phase. Our approach of harnessing a non-hysteretic reversible phase transition region is applicable to other correlated systems exhibiting metal-insulator transitions and can be a potential candidate for oscillator based non-Boolean computing.
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99
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Schick D, Herzog M, Wen H, Chen P, Adamo C, Gaal P, Schlom DG, Evans PG, Li Y, Bargheer M. Localized excited charge carriers generate ultrafast inhomogeneous strain in the multiferroic BiFeO3. PHYSICAL REVIEW LETTERS 2014; 112:097602. [PMID: 24655276 DOI: 10.1103/physrevlett.112.097602] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Indexed: 05/22/2023]
Abstract
We apply ultrafast x-ray diffraction with femtosecond temporal resolution to monitor the lattice dynamics in a thin film of multiferroic BiFeO3 after above-band-gap photoexcitation. The sound-velocity limited evolution of the observed lattice strains indicates a quasi-instantaneous photoinduced stress which decays on a nanosecond time scale. This stress exhibits an inhomogeneous spatial profile evidenced by the broadening of the Bragg peak. These new data require substantial modification of existing models of photogenerated stresses in BiFeO3: the relevant excited charge carriers must remain localized to be consistent with the data.
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100
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Ravichandran J, Yadav AK, Cheaito R, Rossen PB, Soukiassian A, Suresha SJ, Duda JC, Foley BM, Lee CH, Zhu Y, Lichtenberger AW, Moore JE, Muller DA, Schlom DG, Hopkins PE, Majumdar A, Ramesh R, Zurbuchen MA. Crossover from incoherent to coherent phonon scattering in epitaxial oxide superlattices. NATURE MATERIALS 2014; 13:168-72. [PMID: 24317186 DOI: 10.1038/nmat3826] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Accepted: 10/30/2013] [Indexed: 05/27/2023]
Abstract
Elementary particles such as electrons or photons are frequent subjects of wave-nature-driven investigations, unlike collective excitations such as phonons. The demonstration of wave-particle crossover, in terms of macroscopic properties, is crucial to the understanding and application of the wave behaviour of matter. We present an unambiguous demonstration of the theoretically predicted crossover from diffuse (particle-like) to specular (wave-like) phonon scattering in epitaxial oxide superlattices, manifested by a minimum in lattice thermal conductivity as a function of interface density. We do so by synthesizing superlattices of electrically insulating perovskite oxides and systematically varying the interface density, with unit-cell precision, using two different epitaxial-growth techniques. These observations open up opportunities for studies on the wave nature of phonons, particularly phonon interference effects, using oxide superlattices as model systems, with extensive applications in thermoelectrics and thermal management.
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