Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session X37b: Metal Insulator Phase Transitions III: Vanadates and Nickelates |
Hide Abstracts |
Sponsoring Units: DCMP GMAG Chair: Jiang Wei, Tulane University Room: 384 |
Friday, March 17, 2017 8:00AM - 8:12AM |
X37b.00001: Nanoscale control of the metal insulator transition in vanadium oxides using focused ion beam irradiation - fundamental and application perspectives Yoav Kalcheim, Juan Trastoy, Javier Del Valle, Ilya Valmianski, Ivan Schuller Vanadium oxides have long been the focus of intensive research aiming to understand the underlying mechanism of their metal-insulator transitions. These materials are also of interest for applications such as memory devices, bolometers, meta-materials and more. In this study we show that using focused Ga ion irradiation it is possible to suppress the metal-insulator transition with nanometric scale resolution. Aside for shedding light on the mechanism of suppression, this permits the spatial study of the effect of irradiation as well as single step lithography to produce wires of tunable connectivity. Using this technique with deep penetrating ions, it would also be possible to create 3-dimensional wiring patterns in a single lithographic step, with potentially important implications for neuromorphic computation. [Preview Abstract] |
Friday, March 17, 2017 8:12AM - 8:24AM |
X37b.00002: Femtosecond Time-Resolved Nano-Imaging of the Insulator-to-Metal Transition in Vanadium Dioxide Aaron Sternbach, Kyle Lewis, Peter Kissin, Tetiana Slusar, Hyun-Tak Kim, Richard Averitt, Dimitri Basov We have preformed femtosecond time-resolved and nanometer spatially resolved measurements of the insulator-to-metal transition in Vanadium Dioxide (VO$_{\mathrm{2}})$. In order to make this work possible, we have devised and implemented a method for artifact-free nano-imaging with pulsed laser sources. We observe that the transient metallic state is highly inhomogeneous. Following an ultrafast pumping event, a homogeneous increase in near-field signal occurs, which signifies that the initial injection of conduction electrons is homogeneous. This is followed by the inhomogeneous insulator-to-metal transition, which evolves over two distinct timescales from tens to hundreds of picoseconds. Our advances pave a pathway to study a wide range of systems with inhomogeneities properties on the nanoscale with nanoscopic spatial, and ultrafast temporal resolution. [Preview Abstract] |
Friday, March 17, 2017 8:24AM - 8:36AM |
X37b.00003: Finding a metallic chain in strained monoclinic VO$_{2}$ films. Tetiana Slusar, Jin-Cheol Cho, Hyang-Rok Lee, Ki-Ju Yee, Hyun-Tak Kim The microscopic understanding of the electron-electron and electron-phonon interplay is crucial for describing the physics of the insulator-to-metal transition (IMT) in VO$_{2}$ and other strongly correlated systems. The clue on this in VO$_{2}$, particularly, was obtained when the second monoclinic insulating M2 phase was discovered. It is an intermediate phase between monoclinic insulating M1 and rutile metallic R emerging when VO$_{2}$ undergoes structural changes accompanying the IMT. The M2 phase with its two substructures of V-atoms arrangement, a charge-density wave (CDW) and antiferromagnetic insulator-chain (IC), enables the electronic Mott transition via transformation of the IC into a metallic chain (MC) through a breakdown of the electrons correlations. However, the MC has been never observed experimentally. We resolve this issue via the separation of coherent optical phonons originating from different M2 substructures with a subsequent IC-to-MC transformation on IMT. It was measured by ultrafast pump-probe technique that is a unique tool able to sense both structural changes on a femtosecond timescale and the corresponding response of electronic system. This finding decouples the electron-electron and electron-phonon contribution, supporting the Mott IMT. [Preview Abstract] |
Friday, March 17, 2017 8:36AM - 8:48AM |
X37b.00004: Imaging the transition states in the thermal and nonthermal phase transitions of vanadium dioxide using coherent femtosecond electron beams Faran Zhou, Joseph Williams, Zhensheng Tao, David Torres, Nelson Sepulveda, Chong-Yu Ruan Phase transitions are often discussed within the context of thermal equilibrium where distinct phase change phenomena are described in the complex phase diagram in which temperature, chemical doping, or pressure are steady-state tuning parameters. Much less is understood in terms of excited states and dynamical phase transitions induced after sudden excitations using intense laser or electrical pulses.~ Here we present controlled studies to examine the transient emergence of new metastable phases and their nonequilibrium dynamics during photo- and electrically induced phase transitions of vanadium dioxide using femtosecond electron diffraction and diffusive scattering techniques, which allow us to directly monitor the momentum-dependent lattice dynamics.~~~We discover a unique interaction-driven monoclinic emergent state that, interestingly, has a similar crystal symmetry as the thermodynamic M2~phase. Meanwhile, using an excitation pulse below the interaction-drive threshold we also isolate the thermal transitions, following a distinctly different pathway.~ We discuss these results in the context of charge doping, lattice instabilities, static and transient stresses that can invariably influence the phase transitions with potential applications in high-speed electronics.~ [Preview Abstract] |
Friday, March 17, 2017 8:48AM - 9:00AM |
X37b.00005: Correlation-driven metal-insulator transition in Cu$_x$V$_2$O$_5$ nanobeams probed by resistance noise spectroscopy Ali Alsaqqa, Colin Kilcoyne, Ahmed Ali, Justin Andrews, Peter Marley, Sarbajit Banerjee, G. Sambandamurthy Nanoscale vanadium oxide bronzes have attracted interest due to the interesting phenomena they exhibit ranging from charge ordering, superconductivity and metal insulator transitions. We present results from a transport and resistance noise study of single crystalline nanobeams of ${\beta'-\textrm{Cu}_x\textrm{V}_2\textrm{O}_5}$. Resistance noise spectroscopy is a sensitive tool to understand local electronic and structural changes across a phase transition and we employ the method to understand the metal-insulator transition in individual nanobeams of ${\beta'-\textrm{Cu}_x\textrm{V}_2\textrm{O}_5}$. The nanobeams show a metal-insulator transition upon cooling from room temperature with a T$_{MI}\sim$ 210 K. The low-frequency (< 1 Hz) noise magnitude shows a bump-like increase near the phase transition and deviation from a simple 1/f behavior. The probability density function of the resistance fluctuations shows signatures of non-Gaussian fluctuators near the transition and can be interpreted as a strong indicator of a correlation-driven phase transition. The roles of Mott physics, charge ordering and further avenues to tune the transition for potential applications as Mott field effect transistors will be discussed. [Preview Abstract] |
Friday, March 17, 2017 9:00AM - 9:12AM |
X37b.00006: Resistive switching phenomena and metal-insulator transitions in VO$_{\mathrm{2}}$ and V$_{\mathrm{2}}$O$_{\mathrm{3}}$ nanodevices. Javier del Valle, Aliaksei Charnukha, Yoav Kalcheim, Juan Trastoy, Ilya Valmianski, Paul Wang, Dimitri Basov, Ivan K Schuller The VO$_{\mathrm{X}}$ family comprises a large number of oxides, most of which are known to exhibit a Metal-Insulator phase transition (MIT). However, the temperature at which this MIT takes place varies greatly, even for oxides very close in stoichiometry. This makes the study of vacancy drift and filament formation in vanadium oxides an attractive subject, as it can potentially couple two phenomena that have raised much interest: resistive switching and insulating phases in correlated materials. We have fabricated VO$_{\mathrm{2}}$ and V$_{\mathrm{2}}$O$_{\mathrm{3}}$ nanojunctions with a 100-200 nm gap that allows us to apply high electric fields and induce a resistive switching in the sample. Transport measurements after the switching reveal multiple jumps in the resistivity as a function of the temperature, suggesting the formation of new insulating phases. This effect could potentially generate a rich variety of new electrical functionalities in materials presenting a MIT. We thank the AFOSR for financing this research. [Preview Abstract] |
Friday, March 17, 2017 9:12AM - 9:24AM |
X37b.00007: Strain tuning of a Metal-Insulator Transition in SrVO$_{\mathrm{3}}$ films ElĂas Ferreiro-Vila, Hugo Meley, Marta Gibert, Zhenping Wu, Stefano Gariglio, Jean-Marc Triscone SrVO$_{\mathrm{3}}$ is a 3$d^{\mathrm{1}}$ metal with cubic perovskite structure in bulk. Ultrathin films, however, display a dimensional-crossover-driven Metal-Insulator Transition (MIT) as measured by \textit{in situ} photoemission spectroscopy [1]; the ground state for 2 unit cell thick layers is of Mott-Hubbard nature, i.e. the insulating state seems to be driven by electronic correlations, probably enhanced by the reduced dimensionality. Dynamical mean field theory (DMFT) calculations show that this MIT is very sensitive to small changes in the level of epitaxial strain and in thickness [2] making ultrathin SrVO$_{\mathrm{3}}$ films interesting for applications such as sensors and Mott transistors.We report here on investigations of high quality epitaxial films of SrVO$_{\mathrm{3\thinspace }}$grown on a variety of substrates imposing different lattice mismatches. Our transport measurements revealed that the thickness-driven MIT can indeed be tuned via epitaxial strain. As the film thickness is reduced, the films evolve from a metallic behavior to a localized one. At intermediate film thickness, an upturn in resistivity is observed at low temperatures. The thickness at which the crossover occurs depends on the level of strain. [1] K.Yoshimatsu, T. Okabe, H. Kumigashira, S. Okamoto, S. Aizaki, A. Fujimori and M. Oshima. \textit{PRL} \textbf{104,} 147601 (2010). [2]Z. Zhong, M. Wallerberger, J. M. Tomczak, C. Taranto, N. Parragh, A. Toschi, G. Sangiovanni and K. Held, \textit{PRL} \textbf{114}, 246401 (2015). [Preview Abstract] |
Friday, March 17, 2017 9:24AM - 9:36AM |
X37b.00008: Growth and Characterization of Vanadium Dioxide Thin Films for Application in Tunable Metasurfaces Elise Moore, Nathan Kurtz, Adam Ollanik, Brian Riggs, Matthew Escarra Vanadium dioxide (VO2) demonstrates dramatic variation in optical and electronic properties across a metal-insulator transition. The transition, which occurs near room temperature, involves a phase change from monoclinic to tetragonal crystal structure. In order to utilize its unique properties in tunable optical metasurfaces, VO2 thin films are grown using pulsed laser deposition (PLD) on amorphous glass substrates. Raman scattering spectroscopy, x-ray diffraction, and other characterization of the phase transition are used to assess their quality. The most straightforward characterization is done by measuring the resistivity change of a film across the transition temperature (68C). The magnitude of this change is a direct measure of film quality. Electrical characterization of the phase transition is verified and complemented by optical characterization -- analysis of the film's reflectance, transmittance, and refractive index as a function of temperature. These films are then employed in low-loss Huygens optical metasurfaces, which use tunable phase shift in nanoresonators to vary the behavior of light across an interface via a thermal, electrical, or optical stimulus. [Preview Abstract] |
Friday, March 17, 2017 9:36AM - 9:48AM |
X37b.00009: Photoinduced structural dynamics and transformation pathway of sapphire-supported ultrathin vanadium dioxide Ding-Shyue Yang, Xing He, Napat Punpongjareorn, Chonglin Chen, Yuan Lin The complex phase-transition behaviors of vanadium dioxide (VO$_{\mathrm{2}})$ have drawn continual attention because of their strong dependence on a wide range of factors including temperature, strain, doping, photoexcitation, and voltage. Dynamically, ultrafast electron diffraction (UED) with atomic-scale spatial and temporal resolution has been used to unravel the transformation pathway in the photoinduced structural phase transition of VO$_{\mathrm{2}}$, using bulk and nearly strain-free specimens. In this presentation, we report the UED results from 10-nm-thick crystalline VO$_{\mathrm{2}}$ supported on Al$_{\mathrm{2}}$O$_{\mathrm{3}}$(0001) and examine the influence of surface strain on the ultrafast structural transformation. It becomes clear that a complete conversion from the monoclinic phase to the tetragonal lattice does not take place on the time scale of few hundred picoseconds unless a fluence multiple times higher than the thermodynamic enthalpy threshold is used. For some crystalline domains, structural transformation may not be seen even after 1 ns following an intense photoexcitation. The implications of the present and previous observations as well as the transformation pathway will be discussed. [Preview Abstract] |
Friday, March 17, 2017 9:48AM - 10:00AM |
X37b.00010: A photo-induced metastable phase in monoclinic V2O3. Andrej Singer, Juan Gabriel Ramirez, Ilya Valmianski, Ivan K. Schuller, Oleg G. Shpyrko The out of equilibrium pathways recently emerged as a novel paradigm in controlling the order parameters in strongly correlated electron systems. The complex interplay among various degrees of freedom, the hierarchy of the characteristic time scales, and the possibility to dynamically control the nanoscale disorder allows accessing hidden, metastable phases or enhancing the order parameter. Here we couple time-resolved x-ray diffraction experiments with high-resolution nanoscale x-ray imaging to study the properties of the photo-excited structural phase transition (SPT) in the classical material V$_{\mathrm{2}}$O$_{\mathrm{3}}$. We directly observe a non-equilibrium pathway arising during a photo-excited SPT, which is absent in equilibrium measurements. The experiments were conducted at the x-ray free-electron laser LCLS and the synchrotron source APS. [Preview Abstract] |
Friday, March 17, 2017 10:00AM - 10:12AM |
X37b.00011: Electronic structure of H$_{x}$VO$_{\mathrm{2}}$ probed with \textit{in-situ} spectroscopic ellipsometry So Yeun Kim, Luke J. Sandilands, Taedong Kang, Jaeseok Son, C. H. Sohn, Hyojin Yoon, Junwoo Son, S. J. Moon, T. W. Noh Vanadium dioxide (VO$_{\mathrm{2}})$ undergoes a metal-to-insulator transition (MIT) near 340K. Despite extensive studies on this material, the role of electron-electron correlation and electron-lattice interactions in driving this MIT is still under debate. Recently, it was demonstrated that hydrogen can be reversibly absorbed into VO$_{\mathrm{2}}$ thin film without destroying the lattice framework. This H-doping allows systematic control of the electron density and lattice structure which in turn leads to a insulator (VO$_{\mathrm{2}})$ - metal (H$_{x}$VO$_{\mathrm{2}})$ - insulator (HVO$_{\mathrm{2}})$ phase modulation [Yoon \textit{et al.}, Nat. Mat. \textbf{15}, 1113-1119 (2016)]. To better understand the phase modulation of H$_{x}$VO$_{\mathrm{2}}$, we used \textit{in-situ} spectroscopic ellipsometry to monitor the electronic structure during the hydrogenization process, i.e. we measured the optical conductivity of H$_{x}$VO$_{\mathrm{2}}$ while varying $x$. Starting in the high temperature rutile metallic phase of VO$_{\mathrm{2}}$, we observed a large change in the electronic structure upon annealing in H gas at 370K: the low energy conductivity is continuously suppressed, consistent with reported DC resistivity data, while the conductivity peaks at high energy show strong changes in energy and spectral weight. The implications of our results for the MIT in H$_{x}$VO$_{\mathrm{2}}$ will be discussed. [Preview Abstract] |
Friday, March 17, 2017 10:12AM - 10:24AM |
X37b.00012: Magnetic and Crystal Structures in LaVO$_{\mathrm{3}}$ Thin Films under Epitaxial Strain Hugo Meley, Jean Marc Triscone, Stefano Gariglio Interplay between spin, charge, orbital and lattice degrees of freedom is extremely strong and at the origin of numerous phenomena in complex oxides [1]. A remarkable case of lattice-orbit coupling is the Jahn-Teller (JT) effect. LaVO$_{\mathrm{3}}$, a 3d$^{\mathrm{2}}$ compound, exhibits a JT-type cooperative distortion below the 140 K structural phase transition where a mixed G- and C-type orbital order establishes [2]; at higher temperatures, the crystal field due to GdFeO$_{\mathrm{3}}$-type distortion (Pbnm symmetry) imposes a C-type orbital ordering, although with strong orbital fluctuations [3]. We have explored the effect of biaxial strain in epitaxial thin films of LaVO$_{\mathrm{3}}$. X-ray diffraction reveals that the layers accommodate the strain imposed by the substrate assuming different patterns of octahedral tilts and rotations. We used temperature dependent X-ray diffraction, muon spectroscopy and optical conductivity to investigate the film structure under different strain states as well as the orbital and magnetic order. We compare these results with calculations from ab$-$initio theory. [Preview Abstract] |
Friday, March 17, 2017 10:24AM - 10:36AM |
X37b.00013: The role of defects in the electrical properties of NbO$_{\mathrm{\mathbf{2}}}$\textbf{ thin film vertical devices} Toyanath Joshi, Pavel Borisov, David Lederman Epitaxial NbO$_{\mathrm{2}}$ thin films were grown on Si:GaN layers deposited on Al$_{\mathrm{2}}$O$_{\mathrm{3}}$ substrates using pulsed laser deposition. Pulsed current-voltage (IV) curves and self-sustained current oscillations were measured across a 31 nm NbO$_{\mathrm{2}}$ film and compared with a similar device made from polycrystalline NbO$_{\mathrm{2}}$ film grown on TiN-coated SiO$_{\mathrm{2}}$/Si substrate. Crystal quality of the as grown films was determined from x-ray diffractometric, x-ray photoelectron spectroscopy and atomic force microscopy data. The epitaxial film device was found to be more stable than the defect-rich polycrystalline sample in terms of current switching and oscillation behaviors. [Preview Abstract] |
Friday, March 17, 2017 10:36AM - 10:48AM |
X37b.00014: Thickness and substrate dependence of the optical conductivity of niobium dioxide films. D. J. Lahneman, Zhen Xing, Mitchell Polizzi, Melissa Beebe, R. A. Lukaszew, M. M. Qazilbash, S. Kittiwatanakul, J. Lu, S. A. Wolf Niobium dioxide (NbO$_{\mathrm{2}})$ undergoes a temperature induced insulator-to-metal transition accompanied by a crystallographic transition at $^{\mathrm{\sim }}$1080K. Films of different thickness (100 nm and 200 nm) were grown directly on sapphire substrates and on gold coated sapphire substrates. Using Fourier transform infrared spectroscopy and spectroscopic ellipsometry we investigate the room temperature insulating state of NbO$_{\mathrm{2}}$ thin films in the spectral range from $^{\mathrm{\sim }}$100 cm$^{\mathrm{-1}}$ to 50000 cm$^{\mathrm{-1}}$. We observe that at $^{\mathrm{\sim }}$25000 cm$^{\mathrm{-1}}$ there is a shift in the optical interband transition for different films. We discuss the origin of this shift and the implications for the electronic structure. We compare the infrared-active phonons in NbO$_{\mathrm{2}}$ films with those published in the literature on single crystals. The phonons shed light on the strain in the films. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700