Phase transformation in the oxides

Wang, Franklin F. Y.; Gupta, Kedar P.

doi:10.1007/bf02644576

Cited by 20 publications

(14 citation statements)

References 74 publications

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“…The gradual shift of the peak with temperature can be attributed to the continuous increase in the angle of tetragonal distortion with temperature. 12 As seen in Figs. 2͑c͒ and 2͑h͒, we found additional significant electronic ͑"hump"͒ states in the energy range near 170 meV.…”

Section: Results and Analysissupporting

confidence: 57%

“…24 This fully reversible rearrangement of the diffraction spot intensity is then attributed to the enhanced regularity of the in-plane rotations at low temperature, i.e., cubic-to-tetragonal phase transition. 12 Figure 2 shows the Fermi surface and band-structure maps of the STO collected at 150 and 20 K. In the cubic phase at 150 K, we find that the Fermi surface has three degenerate bands centered at ⌫ points and elongated along each principal axis as shown in Fig. 2͑a͒.…”

Section: Results and Analysismentioning

confidence: 99%

“…STO is a band insulator, which experiences a secondorder phase transition from cubic to tetragonal structure at the critical temperature T c of about 105 K. 12 Below T c , neighboring octahedral TiO 6 units start to rotate oppositely about the c axis eventually reaching an angle of 2°as T → 0 ͓Figs. 1͑a͒ and 1͑b͔͒.…”

Section: Introductionmentioning

confidence: 99%

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Structure and correlation effects in semiconductingSrTiO3

et al. 2010

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We have investigated the effects of structure change and electron correlation on SrTiO 3 single crystals using angle-resolved photoemission spectroscopy. We show that the cubic to tetragonal phase transition at 105 K is manifested by a charge transfer from in-plane ͑d yz and d zx ͒ bands to out-of-plane ͑d xy ͒ band, which is opposite to the theoretical predictions. Along this second-order phase transition, we find a smooth evolution of the quasiparticle strength and effective masses. The in-plane band exhibits a peak-dip-hump lineshape, indicating a high degree of correlation on a relatively large ͑170 meV͒ energy scale, which is attributed to the polaron formation.

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Section: Results and Analysissupporting

confidence: 57%

Section: Results and Analysismentioning

confidence: 99%

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Structure and correlation effects in semiconductingSrTiO3

et al. 2010

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“…Intrinsic SrTiO 3 is a band insulator with a ∼3.2 eV gap, and experiences a second-order phase transition from cubic to tetragonal structure at the critical temperature of about 105 K (ref. 18 ). For the present study, both the XAS and ARPES measurements were performed ∼170 K while the low-energy-electron-diffraction (LEED) patterns were taken at room temperature.…”

Section: Resultsmentioning

confidence: 99%

Observation of a two-dimensional liquid of Fröhlich polarons at the bare SrTiO3 surface

et al. 2015

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The polaron is a quasi-particle formed by a conduction electron (or hole) together with its self-induced polarization in a polar semiconductor or an ionic crystal. Among various polarizable examples of complex oxides, strontium titanate (SrTiO3) is one of the most studied. Here we examine the carrier type and the interplay of inner degrees of freedom (for example, charge, lattice, orbital) in SrTiO3. We report the experimental observation of Fröhlich polarons, or large polarons, at the bare SrTiO3 surface prepared by vacuum annealing. Systematic analyses of angle-resolved photoemission spectroscopy and X-ray absorption spectra show that these Fröhlich polarons are two-dimensional and only exist with inversion symmetry breaking by two-dimensional oxygen vacancies. Our discovery provides a rare solvable field theoretical model, and suggests the relevance of large (bi)polarons for superconductivity in perovskite oxides, as well as in high-temperature superconductors.

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“…All measurements presented here were performed in the C M direction (i.e., the [110] direction of the surface Brillouin zone) as shown in Fig. 1(a), and the sample temperature was between 120 K and 150 K (well above the second-order phase transition from cubic to tetragonal structure, which occurs at the critical temperature of T c % 105 K 47,48 ). The approximate k-path probed in the bulk Brillouin zone, can be determined using the free electron final state model, 49,50 where the wave vector perpendicular to the sample is given by…”

Section: Experiments Detailsmentioning

confidence: 99%

Surface electronic structure for various surface preparations of Nb-doped SrTiO₃ (001)

Hatch

Fredrickson

Choi

et al. 2013

Journal of Applied Physics

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Difference in electronic structure between tetragonal and cubic Sr Nb O 2 N J. Appl. Phys. 98, 043706 (2005); 10.1063/1.2032612High-resolution synchrotron-radiation photoemission characterization for atomically-controlled SrTiO 3 ( 001 ) substrate surfaces subjected to various surface treatments High-resolution angle-resolved photoemission spectroscopy (ARPES) was used to study the surface electronic structure of Nb-doped SrTiO 3 (STO) single crystals prepared using a variety of surface preparations. ARPES measurements show that simple degreasing with subsequent anneal in vacuum is not an adequate surface preparation of STO, rather, preparations consisting of etching with buffered HF or HCl, and to a lesser extent, simple water leaching resulted in surfaces with much less disorder. A non-dispersing, mid-gap state was found $800 meV above the top of the valence band for samples which underwent etching. This mid-gap state is not present for vacuum-annealed and water-leached samples, as well as for STO thin films grown using molecular beam epitaxy. Theoretical modeling using density functional theory suggests that this mid-gap state is not related to the SrO-and TiO 2 -terminated surfaces, but rather, is due to a partial hydrogenation of the STO surface that occurs during etching. V C 2013 AIP Publishing LLC.

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Phase transformation in the oxides

Cited by 20 publications

References 74 publications

Structure and correlation effects in semiconductingSrTiO3

Structure and correlation effects in semiconductingSrTiO3

Observation of a two-dimensional liquid of Fröhlich polarons at the bare SrTiO3 surface

Surface electronic structure for various surface preparations of Nb-doped SrTiO₃ (001)

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Phase transformation in the oxides

Cited by 20 publications

References 74 publications

Structure and correlation effects in semiconductingSrTiO3

Structure and correlation effects in semiconductingSrTiO3

Observation of a two-dimensional liquid of Fröhlich polarons at the bare SrTiO3 surface

Surface electronic structure for various surface preparations of Nb-doped SrTiO3 (001)

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Surface electronic structure for various surface preparations of Nb-doped SrTiO₃ (001)