Metastability Phenomena in VO2 Thin Films

Gioacchino, D. Di; Marcelli, A.; Puri, Alessandro; Zou, Chongwen; Fan, Lele; Zeitler, U.; Bianconi, A.

doi:10.3390/condmat2010010

Cited by 15 publications

(9 citation statements)

References 20 publications

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“…The new mesoscopic phase separation with scale free spatial correlation for spin stripes order found here in nickelates is in agreement with previous indications [53][54][55][56][57][58][59] and it provides the experimental smoking gun evidence that the spin ordering in spin stripes phase in nickelates is near a quantum critical point. A similar spatial fractal landscape has been found in cuprates [46][47][48][49][50][51][52] and in other oxides near a quantum phase transition as in VO 2 [60][61][62][63], in ruthenates [64,65], and in diborides [66,67]. The observed scale free phase separation in nickelates is in agreement with the predictions by of the multiband Hubbard model of frustrated phase separation in strongly correlated two bands systems [29,68].…”

Section: Discussionsupporting

confidence: 86%

Direct Visualization of Spatial Inhomogeneity of Spin Stripes Order in La1.72Sr0.28NiO4

et al. 2019

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In several strongly correlated electron systems, the short range ordering of defects, charge and local lattice distortions are found to show complex inhomogeneous spatial distributions. There is growing evidence that such inhomogeneity plays a fundamental role in unique functionality of quantum complex materials. La 1.72 Sr 0.28 NiO 4 is a prototypical strongly correlated perovskite showing spin stripes order. In this work we present the spatial distribution of the spin order inhomogeneity by applying micro X-ray diffraction to La 1.72 Sr 0.28 NiO 4 , mapping the spin-density-wave order below the 120 K onset temperature. We find that the spin-density-wave order shows the formation of nanoscale puddles with large spatial fluctuations. The nano-puddle density changes on the microscopic scale forming a multiscale phase separation extending from nanoscale to micron scale with scale-free distribution. Indeed spin-density-wave striped puddles are disconnected by spatial regions with negligible spin-density-wave order. The present work highlights the complex spatial nanoscale phase separation of spin stripes in nickelate perovskites and opens new perspectives of local spin order control by strain.Condens. Matter 2019, 4, 77 2 of 10 the stripes phases have been the object of interest for decades [1][2][3], while in this last decade new scanning X-ray diffraction methods have been developed due to the ability to focus X-ray synchrotron radiation to micron and sub-micron spots. These methods have made it possible to obtain visualization of spatial topological inhomogeneity of charge density wave order in doped cuprate perovskites [4,5]. Short range generalized Wigner charge density waves have been found to be spatially inhomogeneous with the formation of "striped charge puddles" anti-correlated with competing puddles of "striped dopants rich clusters" [4][5][6]. These experimental results have opened a new era in the long-standing research of complexity in doped strongly correlated perovskites, since they have falsified popular stripes theories which for decades have assumed a homogeneous spatial distribution of spin stripes and charge-stripes. In this work we focus on the spin stripes phase in doped nickelate perovskites. In order to determine the role that the spatial distribution of ordered phases in cuprates plays for the superconductivity, it is instructive to study a non-superconducting reference system like the layered nickelates [7]. Keeping this idea in mind, we push forward the investigation of the spatial distribution of spin-density-wave stripes ordering (SDW-stripes) in La 2-x Sr x NiO 4 nickelates.It is well known that spin stripes appear in layered nickelates [7] in the doping interval 0.15 ≤ x ≤ 0.5 [7]. In the doping range 0.25 < x < 0.3 magnetic stripes and charge stripes can be easily investigated separately. In La 2-x Sr x NiO 4 the spin-order scattering exhibits peaks in the k-space for (1−ε; 0; l) with odd and even l, whereas charge-order scattering always peaks at (2ε; 0; l) with odd l, [7,8] where t...

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Section: Discussionsupporting

confidence: 86%

Direct Visualization of Spatial Inhomogeneity of Spin Stripes Order in La1.72Sr0.28NiO4

et al. 2019

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“…XANES can be particularly useful for probing and mapping the changes in the electronic structure of an MIT transition, providing a correlation between macroscopic observables and microscopic models associated with coexisting metastable configurations, which are tuned by the thickness-dependent misfit strain and stress distributions induced by the mismatch between thin film and substrate [26][27][28]. Since, in the VO 2 electronic MIT-driven transition, a relatively large change in the electronic configuration between the metallic and insulating phases is expected, an accurate measurement of the difference among V 2p X-ray absorption spectra will probe changes of the local 3d orbital occupancy.…”

Section: Discussionmentioning

confidence: 99%

Nanoscale Phase Separation and Lattice Complexity in VO2: The Metal–Insulator Transition Investigated by XANES via Auger Electron Yield at the Vanadium L23-Edge and Resonant Photoemission

et al. 2017

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Among transition metal oxides, VO 2 is a particularly interesting and challenging correlated electron material where an insulator to metal transition (MIT) occurs near room temperature. Here we investigate a 16 nm thick strained vanadium dioxide film, trying to clarify the dynamic behavior of the insulator/metal transition. We measured (resonant) photoemission below and above the MIT transition temperature, focusing on heating and cooling effects at the vanadium L 23 -edge using X-ray Absorption Near-Edge Structure (XANES). The vanadium L 23 -edges probe the transitions from the 2p core level to final unoccupied states with 3d orbital symmetry above the Fermi level. The dynamics of the 3d unoccupied states both at the L 3 -and at the L 2 -edge are in agreement with the hysteretic behavior of this thin film. In the first stage of the cooling, the 3d unoccupied states do not change while the transition in the insulating phase appears below 60 • C. Finally, Resonant Photoemission Spectra (ResPES) point out a shift of the Fermi level of~0.75 eV, which can be correlated to the dynamics of the 3d // orbitals, the electron-electron correlation, and the stability of the metallic state.

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“…Advances on quantum mechanics of orbital physics which is today a hot topic have been obtained by Oleś group showing orbital dilution in d 4 oxides by tuning crystal field potential [96] and magnetic properties of crystalline and ferroelectric layered rare-earth-titanate by Kuznetsov et al [97]. Strain Induced orbital dynamics across the metal insulator transition in thin VO 2 films [98] provide further information on nanoscale phase separation in the correlation-driven insulator-metal transition in vanadium dioxide [99][100][101][102]. The theoretical studies on nanoscale phase separation observed in cuprates [103][104][105][106] have focused on the coexistence of a metallic phase with a spin density wave phase controlled by pressure [107] of the nucleation of magnetic micro-inhomogeneity induced by an electric field [108] the order-disorder transition in a system made of two electronic components induced by nearest-neighbor repulsion [109].…”

Section: The Superstripes 2019 Conferencementioning

confidence: 99%

Superconductivity in Quantum Complex Matter: the Superstripes Landscape

Bianconi

2020

J Supercond Nov Magn

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While in XX century the theory of superconductivity has focused on a homogeneous metal with a rigid lattice which can be reduced to a single effective conduction band in the dirty limit. Today in the XXI century, the physics of superconductivity is focusing on complexity of quantum matter where novel quantum functionalities with lattice inhomogeneity at nanoscale (between 1 nm and 100 nm) and at mesoscopic scale (in the range 100-10000 nm), where the electronic structure need to be described by multiple Fermi surfaces and multiple gaps in the superconducting phase in the clean limit. The present issue of Journal of superconductivity and Novel magnetism collects papers presented at the

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Metastability Phenomena in VO2 Thin Films

Cited by 15 publications

References 20 publications

Direct Visualization of Spatial Inhomogeneity of Spin Stripes Order in La1.72Sr0.28NiO4

Direct Visualization of Spatial Inhomogeneity of Spin Stripes Order in La1.72Sr0.28NiO4

Nanoscale Phase Separation and Lattice Complexity in VO2: The Metal–Insulator Transition Investigated by XANES via Auger Electron Yield at the Vanadium L23-Edge and Resonant Photoemission

Superconductivity in Quantum Complex Matter: the Superstripes Landscape

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