Metallization of vanadium dioxide driven by large phonon entropy

Budai, J. D.; Hong, Jiawang; Manley, M. E.; Specht, E. D.; Li, Chen W.; Tischler, J. Z.; Abernathy, D. L.; Said, Ayman; Leu, Bogdan M.; Boatner, L. A.; McQueeney, R. J.; Delaire, Olivier

doi:10.1038/nature13865

Cited by 292 publications

(303 citation statements)

References 44 publications

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“…While this approximation has been used successfully in a wide range of applications, [97][98][99][100][101][102][103][104] we show that it fails to accurately represent the electronic structure under the Floquet-phonon conditions. The frozen phonon approximation cannot account for the dynamical dressing effect that the coherently oscillating lattice supplies to the electronic structure.…”

Section: -83mentioning

confidence: 99%

Phonon Driven Floquet Matter

2018

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The effect of electron-phonon coupling in materials can be interpreted as a dressing of the electronic structure by the lattice vibration, leading to vibrational replicas and hybridization of electronic states. In solids a resonantly excited coherent phonon leads to a periodic oscillation of the atomic lattice in a crystal structure bringing the material into a non-equilibrium electronic configuration. Periodically oscillating quantum systems can be understood in terms of Floquet theory, which has a long tradition in the study of semi-classical light-matter interaction. Here, weshow that the concepts of Floquet analysis can be applied to coherent lattice vibrations reflecting the underlying coupling mechanism between electrons and coherent bosonic modes. This coupling leads to phonon-or photon-dressed quasi-particles imprinting specific signatures in the spectrum of the electronic structure. Such dressed electronic states can be detected by time-and angularresolved photoelectron spectroscopy (ARPES) manifesting as sidebands to the equilibrium band structure. Taking graphene as a paradigmatic material with strong electron-phonon interaction and non-trivial topology we show how the phonon-dressed states display an intricate sideband structure revealing the electron-phonon coupling at the Brillouin zone center and topological ordering of the Dirac bands. Most strikingly, we find that the non-equilibrium electronic structure created by coherent dynamical dressing is the same for photon and phonon perturbations. We demonstrate that if time-reversal symmetry is broken by the coherent lattice perturbations a topological phase transition can be induced. This work establishes that the recently demonstrated concept of lightinduced non-equilibrium Floquet phases can also be applied when using coherent phonon modes for the dynamical control of material properties. The present results are generic for bosonic timedependent perturbations, therefore we envision similar phenomena to be observed for example for plasmon, magnon or exciton driven materials.

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Section: -83mentioning

confidence: 99%

Phonon Driven Floquet Matter

2018

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“…Different schemes have been suggested to explain the strain induced T MIT variation, including strong electronic correlations [57,58] and orbital control [35,54] but the microscopic mechanism behind the strain modulation remains unclear. Regarding the MIT in general, it is likely that both correlations and structural effects must be taken into account [10,[59][60][61]. Independent of the precise microscopic mechanism, mesoscopic physics certainly is extremely important in these samples.…”

Section: Samplesmentioning

confidence: 99%

Phase transition in bulk single crystals and thin films ofVO2by nanoscale infrared spectroscopy and imaging

et al. 2015

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We have systematically studied a variety of vanadium dioxide (VO 2 ) crystalline forms, including bulk single crystals and oriented thin films, using infrared (IR) near-field spectroscopic imaging techniques. By measuring the IR spectroscopic responses of electrons and phonons in VO 2 with sub-grain-size spatial resolution (~20 nm), we show that epitaxial strain in VO 2 thin films not only triggers spontaneous local phase separations but also leads to intermediate electronic and lattice states that are intrinsically different from those found in bulk. Generalized rules of strain and symmetry dependent mesoscopic phase inhomogeneity are also discussed. These results set the stage for a comprehensive understanding of complex energy landscapes that may not be readily determined by macroscopic approaches.

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“…Mott-like transition, [18][19][20] but also strong coupling to phonon modes and doubling of the unit-cell. [21] In VO2 thin films and nano-beams, the transition develops through a spatially phase separated state [8,10,22] that may affect the dynamics of the transition.Phase separation is complicated by at least one additional insulating phase for which a solid state triple point was identified. [23] Further modification can be achieved by substrate and local strain, which alter the VO2 electronic properties [18] or control the phase separation.…”

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confidence: 99%

Ramp‐Reversal Memory and Phase‐Boundary Scarring in Transition Metal Oxides

et al. 2017

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Transition metal oxides (TMOs) are complex electronic systems which exhibit a multitude of collective phenomena. Two archetypal examples are VO2 and NdNiO3, which undergo a metal-insulator phase-transition (MIT), the origin of which is still under debate. Here we report the discovery of a memory effect in both systems, manifest through an increase of resistance at a specific temperature, which is set by reversing the temperature-ramp from heating to cooling during the MIT. The characteristics of this ramp-reversal memory effect do not coincide with any previously reported history or memory effects in manganites, electronglass or magnetic systems. From a broad range of experimental features, supported by theoretical modelling, we find that the main ingredients for the effect to arise are the spatial Submitted to 22222222224222 phase-separation of metallic and insulating regions during the MIT and the coupling of lattice strain to the local critical temperature of the phase transition. We conclude that the emergent memory effect originates from phase boundaries at the reversal-temperature leaving "scars" in the underlying lattice structure, giving rise to a local increase in the transition temperature.The universality and robustness of the effect shed new light on the MIT in complex oxides.TMOs are a hallmark example of complex electron systems; the competition between charge, spin, strain, lattice, oxidation and other degrees of freedom, having similar energy scales, give rise to numerous collective phenomena [1][2][3] including superconductivity, [4] colossal magnetoresistance [5] and metal-insulator transitions (MIT). [6] In many thin film TMOs which exhibit a temperature (T)-driven phase transition, complexity is manifest through the coexistence of multiple phases where a single phase is expected, [7][8][9][10][11] providing the setting required for emergent phenomena to develop.[1]An intriguing feature found in many of the systems that exhibit the aforementioned phenomena, is the appearance of internal memory, where the system's properties (e.g. resistance or magnetization) depend on the measurement history. Such memory effects appear in various forms and measurement settings, having very different microscopic origins, many of which are still poorly understood. Examples include dynamical memory and slow relaxation in electron-glass systems such as amorphous oxides, [12,13] spatially phase-separated memory in colossal-magnetoresistance manganites, [14] shape-memory in martensitic alloys, [15] and more. [16,17] Here we report the appearance of an unexpected memory effect within the MIT in two prototypical examples of complex TMOs, namely VO2 and NdNiO3 (NNO). The characteristics of the observed effect differ substantially from those of previously reported memory effects, indicating a different microscopic origin.VO2 and NNO both exhibit an MIT, however its features and microscopic origin are quite different. In VO2 the MIT occurs above room temperature, ~340 K, and is accompanied by a structural transition from...

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Metallization of vanadium dioxide driven by large phonon entropy

Cited by 292 publications

References 44 publications

Phonon Driven Floquet Matter

Phonon Driven Floquet Matter

Phase transition in bulk single crystals and thin films ofVO2by nanoscale infrared spectroscopy and imaging

Ramp‐Reversal Memory and Phase‐Boundary Scarring in Transition Metal Oxides

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