Changes in the electronic structure of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Ti</mml:mi></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">O</mml:mi></mml:mrow><mml:mrow><mml:mn>7</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>across the semicondu

Abbate, M.; Potze, R.; Sawatzky, G. A.; Schlenker, C.; Lin, Hong‐Ji; Tjeng, L. H.; Chen, C. T.; Teehan, D.; Turner, Tracy

doi:10.1103/physrevb.51.10150

Cited by 42 publications

(28 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In contrast, the PES spectra in the Ti 3d band region show strong temperature dependence as shown in Fig. 1 (b), being consistent with the previous results for the M and LI phases with a lower energy resolution [16]. Here, the sample was first cooled and then heated as indicated in the figure, so as to cross twice each transition temperature.…”

supporting

confidence: 72%

See 1 more Smart Citation

Disorder effects in the bipolaron system Ti ₄ O ₇ studied by photoemission spectroscopy

Kobayashi¹,

Susaki²,

Fujimori³

et al. 2002

Europhys. Lett.

View full text Add to dashboard Cite

We have performed a photoemission study of Ti4O7 around its two transition temperatures so as to cover the metallic, high-temperature insulating (bipolaron-liquid), and low-temperature insulating (bipolaron-crystal) phases. While the spectra of the low-temperature insulating phase show a finite gap at the Fermi level, the spectra of the high-temperature insulating phase are gapless, which is interpreted as a soft Coulomb gap due to dynamical disorder. We suggest that the spectra of the high-temperature disordered phase of Fe3O4, which exhibits a charge order-disorder transition (Verwey transition), can be interpreted in terms of a Coulomb gap.PACS numbers: 71.30.+h, 72.80.Ga, Since Mott [1] proposed the idea of variable-range hopping and minimum metallic conductivity for disordered systems and Anderson [2] raised the concept of localization due to disorder, physical properties of disordered solids have been extensively studied. Influence of Coulomb interaction on the electronic density of states (DOS) near the Fermi level (E F ) of disordered systems is one of the most fundamental issues to be clarified. Efros and Shklovskii [3] proposed that in disordered insulators long-range Coulomb interaction opens a soft Coulomb gap (SCG), whose DOS is proportional to (E − E F ) 2 . So far, there have been tunneling spectroscopic confirmations of the SCG in some disordered systems such as doped semiconductors [4]. Davies and Franz [5] pointed out the possibility of an SCG opening in the photoemission spectra of Na x Ta y W 1−y O 3 [6], but the experiments did not have sufficient energy resolution to critically address this problem. Another important issue is how short-range order (SRO) affects DOS near E F , that is, how the electronic structure evolves when a charge ordering develops from disorder to SRO to long-range order.Ti 4 O 7 is a suitable system to study the above problems: It undergoes successive phase transitions with decreasing temperature from a metal to a charge-ordered insulator via an insulator with SRO [7]. It is a system with nominally 0.5 3d electron per Ti, allowing two possible valence states of Ti 3+ (3d 1 ) and Ti 4+ (3d 0 ), and attracted particular attention in 1970's as a system where bipolarons, or singlet pairs of two polarons, are formed in real space [7][8][9]. Above T MI = 154 K, the system is in the metallic (M) phase and the Ti valence is believed to be uniform 3.5+ as shown in Fig. 1 (a). That is, the electrical resistivity ρ(T ) is metallic with Pauliparamagnetic χ(T ). With decreasing temperature, singlet Ti 3+ -Ti 3+ pairs, namely bipolarons, are formed, resulting in the metal-to-insulator transition at T MI with a steep increase in ρ(T ) by three orders of magnitude. At the same time, χ(T ) almost vanishes, reflecting the formation of the singlet bipolarons. We refer to this phase as the high-temperature insulating (HI) phase. Because the bipolarons are dynamically disordered in this phase as has been established by EPR studies [10], the HI phase may be called a bipolaron liquid. Sub...

show abstract

supporting

confidence: 72%

“…The position and the width of the O 2p band (not shown) show almost no temperature dependence across the two phase transitions as in the previous photoemission study [16]. In contrast, the PES spectra in the Ti 3d band region show strong temperature dependence as shown in Fig.…”

mentioning

confidence: 64%

Disorder effects in the bipolaron system Ti ₄ O ₇ studied by photoemission spectroscopy

Kobayashi¹,

Susaki²,

Fujimori³

et al. 2002

Europhys. Lett.

View full text Add to dashboard Cite

show abstract

“…For the former, there is no conclusive experimental data on the band-gap energy and for the latter, as to our knowledge, no reports at all. The band gap of Ti 4 O 7 is reported to be 0.041 eV from conductivity measurements [62], 0.6 eV from spectroscopy data [63], and 0.25 eV from optical transmission data [64]. In principle, both HSE and U = 5 result in compatible band gaps.…”

Section: B Electronic and Magnetic Propertiesmentioning

confidence: 98%

TinO2n−1Magnéli phases studied using density functional theory

et al. 2014

View full text Add to dashboard Cite

Defects in the rutile TiO 2 structures have been extensively studied, but the intrinsic defects of the oxygendeficient Ti n O 2n−1 phases have not been given the same amount of consideration. Those structures, known as Magnéli phases, are characterized by the presence of ordered planes of oxygen vacancies, also known as shear planes, and it has been shown that they form conducting channels inside TiO-based memristor devices. Memristors are excellent candidates for a new generation of memory devices in the electronics industry. In this paper we present density-functional-theory-based electronic structure calculations for Ti n O 2n−1 Magnéli structures using PBESol+U (0 U 5 eV) and Heyd-Scuseria-Ernzerhof functionals, showing that intrinsic defects present in these structures are responsible for the appearance of states inside the band gap, which can act as intrinsic dopants for the enhanced conductivity of TiO 2 memristive devices.

show abstract

“…They proposed a mechanism for the metal-insulator transition related to the disorder of the Ti +3 pairs. Abbatte et al 25 presented results of photoemission spectroscopy and x-ray absorption spectra ͑XAS͒ within the 50-300 K range. They studied Ti 4 O 7 's electronic structure across the semiconductor-semiconductor and semiconductor-metal transitions.…”

Section: Introductionmentioning

confidence: 99%

“…The Ti +3 ions are ordered in alternate Ti +3 -Ti +3 pairs up to 150 K above which temperature the Ti +3 -Ti +3 pairs separate and all equivalent titanium ions adopt an average electronic charge-Ti +3. 5 Abbatte et al 25 Lakkis et al 26 combined x-ray diffraction with electron paramagnetic resonance studies. They proposed a mechanism for the metal-insulator transition related to the disorder of the Ti +3 pairs.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamics of oxygen defective Magnéli phases in rutile: A first-principles study

Liborio

Harrison

2008

Phys. Rev. B

View full text Add to dashboard Cite

Ab initio thermodynamics has been used to calculate the formation energies, in different environmental conditions, for a number of oxygen-defective structures in rutile. In addition to the Ti n O 2n−1 ͑3 ഛ n ഛ 5͒ Magnéli phases, the two fundamental points defects, Ti interstitials and neutral oxygen vacancies, were also considered. The predicted phase stability is compared to available experimental data and there is reasonable agreement between the calculated phase boundaries and those observed. These results are used to discuss a mechanism that has been proposed as an explanation for the formation of the crystallographic shear planes in rutile.

show abstract

Changes in the electronic structure ofTi4O7across the semicondu

Cited by 42 publications

References 29 publications

Disorder effects in the bipolaron system Ti ₄ O ₇ studied by photoemission spectroscopy

Disorder effects in the bipolaron system Ti ₄ O ₇ studied by photoemission spectroscopy

TinO2n−1Magnéli phases studied using density functional theory

Thermodynamics of oxygen defective Magnéli phases in rutile: A first-principles study

Contact Info

Product

Resources

About

Changes in the electronic structure ofTi4O7across the semicondu

Cited by 42 publications

References 29 publications

Disorder effects in the bipolaron system Ti 4 O 7 studied by photoemission spectroscopy

Disorder effects in the bipolaron system Ti 4 O 7 studied by photoemission spectroscopy

TinO2n−1Magnéli phases studied using density functional theory

Thermodynamics of oxygen defective Magnéli phases in rutile: A first-principles study

Contact Info

Product

Resources

About

Disorder effects in the bipolaron system Ti ₄ O ₇ studied by photoemission spectroscopy

Disorder effects in the bipolaron system Ti ₄ O ₇ studied by photoemission spectroscopy