Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session L44: Metal-Insulator Phase Transition ILive
|
Hide Abstracts |
Sponsoring Units: DCMP Chair: John Harter, University of California, Santa Barbara |
Wednesday, March 17, 2021 8:00AM - 8:12AM Live |
L44.00001: Coherent phonons and the interplay between charge density wave and Mott phases in 1T-TaSe2 Charles Sayers, Hamoon Hedayat, Ariana Ceraso, Flavien Museur, Mattia Cattelan, Lewis Hart, Liam Farrar, Stefano Dal Conte, Giulio Cerullo, Claudia Dallera, Enrico Da Como, Ettore Carpene 1T-TaSe2 is an ideal system in which to explore the phenomenon of coexisting order since it is host to both a charge density wave (CDW) and Mott phase at low temperature. We investigated the CDW-Mott phase in 1T-TaSe2 at 77 K using a combination of time- and angle-resolved photoemission spectroscopy (TR-ARPES) and time-resolved reflectivity (TRR) which reveals strong coherent phonon oscillations [1]. Most importantly, we find that perturbation using a femtosecond laser pulse in TR-ARPES triggers a modulation of the Mott gap with a single frequency related to the in-plane CDW amplitude mode, whereas TRR measurements show a modulation comprised of multiple frequencies belonging to the distorted CDW lattice modes. Our results clearly identify the relationship of the in-plane CDW amplitude mode with the Mott phase in 1T-TaSe2 and highlight the importance of lattice degrees of freedom. |
Wednesday, March 17, 2021 8:12AM - 8:24AM Live |
L44.00002: Structural Manipulation of Phase Transitions by Self-induced Strain in Geometrically Confined Thin Films Yoav Kalcheim, Coline Adda, Pavel Salev, Minhan Lee, Nareg Ghazikhanian, Nicolas M Vargas, Javier del Valle, Henry Navarro, Ivan K Schuller Strain engineering is used very frequently to tune material properties in thin films. The most studied sources of strain are lattice mismatch and differential thermal contraction between the substrate and film. However, we show that in materials which undergo a structural phase transition (SPT), a third and often overlooked source of strain may play a very significant role. If the substrate confines the area of the film, the SPT may induce stress which changes the evolution of the transition. This is a 2D analog of the isochoric water-ice transition, where the freezing point drops below 0°C. |
Wednesday, March 17, 2021 8:24AM - 8:36AM Live |
L44.00003: Unraveling the role of V-V dimer on the vibrational properties of VO2 by first-principles simulations and Raman spectroscopic analysis Wasim Mondal, Egor Evlyukhin, Sebastian Alphonso Howard, Galo Paez Fajardo, Hanjong Paik, Darrell Schlom, Louis F. J. Piper, Wei-Cheng Lee We investigate the vibrational properties of VO2, particularly the low temperature M1 phase using the density functional theory as well as Raman spectroscopy. We perform the structural optimization using SCAN meta-GGA functional and obtain the optimized crystal structures not only with the correct energy hierarchy for the rutile and M1 phases, but also phonon properties in great agreement with previous neutron scattering measurement as well as Raman spectroscopic measurements presented in this work. Based on the harmonic approximation around the optimized structures at zero temperature, we reproduce the phonon softening in the rutile phase as well as the phonon stiffening in the M1 phase. In addition, we perform Raman experiments on VO2 thin films which stimulate enormous interests in the field of thin-film engineering for transition metal oxides. We demonstrate from the comparison between theoretical calculations and Raman measurements that the subtle change of the V-V dimer due to the strain effect can be reliably detected by the Raman spectroscopy, which could be a new framework to determine the subtle change of crystal structure for transition metal oxide thin films. |
Wednesday, March 17, 2021 8:36AM - 8:48AM Live |
L44.00004: Observation of the insulator to metal transition in VO2 by non-contact AFM Alyson Spitzig, Michael Arumainayagam, Elizabeth Guo, Xuguang Wang, Dilek Yildiz, Jason D Hoffman, Jenny E. Hoffman VO2 undergoes an insulator to metal transition (IMT) with a conductivity increase up to 5 orders of magnitude upon heating through 340 K. The interplay between Joule heating and electric field effects on inducing the IMT is an active area of research. Here we present non-contact atomic force microscopy (nc-AFM) measurements from a VO2 film grown with oxygen plasma-assisted MBE. In nc-AFM, an oscillating qPlus sensor can locally and non-invasively detect the force and power dissipation between the tip and sample. As we ramp the voltage applied to the sample, we observe a rise and subsequent drop in the power dissipated, indicating the film has switched to the metallic state. We match the pre-transition power dissipated to Joule dissipation, highlighting the crucial role local heating plays in triggering the IMT in VO2. |
Wednesday, March 17, 2021 8:48AM - 9:00AM Live |
L44.00005: Near-Field Forces and Non-Contact Dissipation in VO2 Films Elizabeth Guo, Alyson Spitzig, Michael Arumainayagam, Dilek Yildiz, Jason D Hoffman, Jenny E. Hoffman Two theories can describe how VO2 undergoes its insulator-to-metal transition (IMT) at 340 K: it may exhibit a Mott transition; or exhibit a Peierls or structural phase transition (SPT) due to electron-phonon interactions. To study the IMT of VO2, we use the non-invasive technique of non-contact atomic force microscopy (nc-AFM). When the oscillating conducting tip of the nc-AFM approaches a VO2 film grown by molecular beam epitaxy, we detect a resonant frequency shift of the tuning fork sensor, related to tip-sample forces. We also increase the driving bias to maintain a constant tip response amplitude, related to tip-sample power dissipation. Preliminary data shows a rise in the power dissipated in the high force regime, suggesting phononic dissipation which may signal proximity to a phase transition. We expect power dissipation to change across the structural phases of VO2 due to differing lattice symmetries and phonon spectra. Thus, we study the role of phonon dispersion in the insulating and metallic states of VO2 in order to understand the dissipative nature of the SPT. |
Wednesday, March 17, 2021 9:00AM - 9:12AM Live |
L44.00006: Simultaneous Structural and Electronic Transitions in Epitaxial VO2/TiO2(001) Galo Paez Fajardo, Christopher Singh, Matthew J Wahila, Keith E. Tirpak, Nicholas F. Quackenbush, Shawn Sallis, Hanjong Paik, Yufeng Liang, Darrell Schlom, christoph Schlueter, Tien-Lin Lee, Wei-Cheng Lee, Louis F. J. Piper VO2 is known to undergoes a metal-to-insulator transition (MIT) near room temperature in concomitance with a structural phase transition (SPT) from a rutile to a monoclinic phase. However, the Mott versus Peierls nature of the transition is still under debate. Recently several studies [1] have reported an electron-correlation driven MIT of VO2 without a corresponding SPT under certain conditions. Here we will present a temperature dependence study [2] of biaxially stretched, epitaxial VO2 films grown by molecular beam epitaxy on TiO2(001) employing x-ray standing waves and hard x-ray photoelectron spectroscopy, which are sensitive to the interplanar distance along the V-V dimer direction and the metallicity of VO2, respectively. This combined study allowed us to monitor simultaneously the MIT and SPT of the strained VO2 films, which were found to occur concurrently within ±1 K. Comparison of our DFT modelling with the spectroscopic data further supports a cooperative Mott-Peierls description of the transition for VO2. |
Wednesday, March 17, 2021 9:12AM - 9:24AM Live |
L44.00007: Real-space cluster dynamical mean-field theory: Center focused extrapolation on the one- and two particle level Marcel Klett, Nils Wentzell, Thomas Schaefer, Fedor Simkovic, Olivier Parcollet, Sabine Andergassen, Philipp Hansmann We revisit the cellular dynamical mean-field theory (CDMFT) for the single band Hubbard model on the square lattice at half filling, reaching real-space cluster sizes of up to 9 x 9 sites. Using benchmarks against direct lattice diagrammatic Monte Carlo at high temperature, we show that the self-energy obtained from a cluster center focused extrapolation converges faster with the cluster size than the periodization schemes previously introduced in the literature. The same benchmark also shows that the cluster spin susceptibility can be extrapolated to the exact result at large cluster size, even though its spatial extension is larger than the cluster size. |
Wednesday, March 17, 2021 9:24AM - 9:36AM Live |
L44.00008: Filament dynamics in the voltage-driven insulator-to-metal transition Javier del Valle, Nicolas M Vargas, Pavel Salev, Rodolfo Rocco, Claribel Dominguez Ordonez, Jennifer Fowlie, Pavel Lapa, Yoav Kalcheim, Coline Adda, Minhan Lee, Stefano Gariglio, Marcelo Rozenberg, Jean-Marc Triscone, Ivan Schuller Certain correlated oxides feature an insulator-to-metal transition which can be triggered by applying an external voltage: the material becomes conducting if a threshold electric field is exceeded. This phenomenon is known as voltage-driven IMT, and it has very promising applications in emerging technologies such as optoelectronics and neuromorphic computing. While it is known that this process takes place in a filamentary way, it is not yet known how these filaments nucleate, grow and relax. We combine reflectivity and transport measurements to image metallization with spatial and temporal resolution. Five correlated oxides from two different families are analyzed: VO2, V2O3, V3O5, NdNiO3 and SmNiO3, finding remarkable differences in the filament expansion process. By comparing these systems and with the insight of numerical simulations, we identify the key parameters that govern the dynamics of the voltage-driven IMT. |
Wednesday, March 17, 2021 9:36AM - 9:48AM Live |
L44.00009: Joule heating simulations of VO2 films Michael Arumainayagam, Alyson Spitzig, Elizabeth Guo, Xuguang Wang, Dilek Yildiz, Jason D Hoffman, Jenny E. Hoffman Vanadium dioxide (VO2) undergoes an insulator-to-metal transition (IMT) when heated above 340 K. Recent studies have shown that an applied voltage can trigger the IMT, but it is still unclear whether the electric field or Joule heating drives the transition. To investigate the role of Joule heating in the voltage-triggered IMT, we used conductive atomic force microscopy (CAFM), which employs a biased tip in contact mode to measure the local current through a VO2 film. Here we present a computational study of Joule heating in a VO2 film due to CAFM bias sweeps. We use COMSOL Multiphysics, a finite element analysis software, to determine the local temperature and electric field prior to the IMT. This Joule heating model can reproduce the IV characteristics of the CAFM experimental data, confirming the importance of Joule heating in inducing the IMT. We extend our simulations to non-contact AFM dissipation measurements, in which the role of Joule heating in VO2 is determined as a function of temperature and voltage, and the additional parameters of tip-sample distance and tip oscillation amplitude. |
Wednesday, March 17, 2021 9:48AM - 10:00AM Live |
L44.00010: Out-of-equilibrium dynamics in a 2D electron system with screened Coulomb interactions Lily Stanley, Dragana Popovic Considerable experimental evidence suggests that Coulomb interactions are responsible for a variety of phenomena observed in the metallic regime of 2D systems, as well as for glassy behavior near the 2D metal-insulator transition (MIT) and in the insulating regime. In particular, in both low- and high-disorder systems, the insulating state is a Coulomb glass. To address the fundamental question whether glassy behavior of electrons exists in the absence of long-range Coulomb interactions, we studied strongly disordered 2D electrons in thin-oxide Si devices in which the Coulomb interaction is screened by the nearby metallic gate. We measured the relaxations of conductivity after excitation out of equilibrium made by a large change of carrier density ns, over a wide range of temperatures and ns, spanning the 2D MIT. The results show differences in the dynamics compared to the case of long-range interactions, indicating the key role of long-range Coulomb interactions in the existence of glassy behavior of electrons near the 2D MIT in strongly disordered samples. |
Wednesday, March 17, 2021 10:00AM - 10:12AM Live |
L44.00011: Tunneling injection of doublon-like excitations and their coupling to the charge density wave in 1T-TaS2 Christopher J. Butler, Masaro Yoshida, Tetsuo Hanaguri, Yoshihiro Iwasa In 1T-TaS2, it is known that an electron-phonon-driven charge density wave precedes a Mott insulating ground state, but much about the nature of each of these phenomena has yet to be established. Fresh insights may be gained from observing the dynamics of the coupled lattice and charge degrees of freedom. Here, we observe the dynamic response to tunneling injection of single electrons, facilitated using a scanning tunneling microscope. This reveals unusual narrow electronic excitations at the upper Hubbard band onset, and their apparent electron-phonon replicas. The replicas likely stem from excitation of amplitude mode phonons associated with the 'Star-of-David' charge density wave. The narrow electronic excitations themselves may hint at coherent quasiparticles, polaronic bound states, or an as yet unknown phenomenon of strongly correlated and electron-phonon coupled systems. These observations may extend our microscopic understanding of systems in which electronic correlations and electron-phonon coupling are both strong, and should spur a new theoretical push to understand the excitations which arise. |
Wednesday, March 17, 2021 10:12AM - 10:24AM Live |
L44.00012: A Systematic Study of V1-xMoxO2 Correlation Length as a Function of Mo Composition and Temperature Tyra C Douglas, Matthew A Davenport, Logan M. Whitt, Top B Rawot Chhetri, Matthew Krogstad, Stephan Rosenkranz, Raymond Osborn, Jared Allred
|
Wednesday, March 17, 2021 10:24AM - 10:36AM Live |
L44.00013: Electron-Phonon Coupled Materials in Nonequilibrium Ryan Nesselrodt, James Freericks Advances in the capability of pump-probe spectroscopy experiments present the opportunity to explore the coupled degrees of freedom in complex materials, as well as to reveal novel nonequilibrium features. Since the electrons are pumped to high energy, it is a reasonable approximation to consider a model of electrons coupled to static phonons. We examine the case of the Holstein model and we present the results for an exact solution of time-resolved ARPES data for phonon mediated charge-density-wave systems. The calculations are able to run to long times and include all perturbative and intrinsic anharmonic effects. We compare these computational results to experiments. |
Wednesday, March 17, 2021 10:36AM - 10:48AM Live |
L44.00014: Fragile 3D Order in V(1-x)MoxO2 Matthew Krogstad, Matthew A Davenport, Logan M. Whitt, Stephan Rosenkranz, Raymond Osborn, Jared Allred VO2 displays a metal-insulator phase transition near 340 K. Accompanying this electronic transition is a structural transition. The connection between these two transitions is unclear, with electronically-driven and structurally-driven models providing conflicting results. Electron doping via molybdenum substitution enhances metallicity and reduces the structural transition temperature; between 17% and 19% Mo, we find that the long-range structural transition is suppressed entirely while the electronic transitions remain similar. |
Wednesday, March 17, 2021 10:48AM - 11:00AM Live |
L44.00015: Abrupt structural transition in V2O3 revealed by pair distribution function analysis Ethan Fletcher, Benjamin Frandsen, Hiroshi Kageyama, Kentaro Higashi V2O3 is an important material for the study of Mott insulators and other strongly correlated electron systems. Despite decades of research, a complete understanding of the metal-insulator transition in V2O3 has not been conclusively established. Here, we present comprehensive atomic and magnetic pair distribution function (PDF) analyses of V2O3 using both x-ray and neutron total scattering measurements, shedding new light on the mechanism of the transition from the point of view of short-range structural and magnetic correlations on both sides of the transition. We observe an abrupt structural transition with no hint of short-range monoclinic distortions above the transition temperature. This lack of structural fluctuations above the transition contrasts with the known presence of magnetic fluctuations in the high-temperature state, suggesting that the lattice degree of freedom plays a secondary role behind the spin degree of freedom in the transition mechanism. |
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. |
© 2025 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