Chiral symmetry restoration in anisotropic<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mi>QED</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math>

Thomas, Iorwerth O.; Hands, Simon

doi:10.1103/physrevb.75.134516

Cited by 33 publications

(39 citation statements)

References 43 publications

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“…We plot the SX-PES and HAXPES on an enlarged (×5) scale and normalized to the main peak intensity (inset Fig. 1 states [24,25]. A similar behaviour was recently found for the 2D-electron gas at SrTiO 3 -LaAlO 3 interface using HAXPES [26].…”

supporting

confidence: 55%

Role of Ti3dCarriers in Mediating the Ferromagnetism ofCo∶TiO2Anatase Thin Films

et al. 2011

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We study the surface and bulk electronic structure of the room-temperature ferromagnet Co:TiO2 anatase films using soft and hard x-ray photoemission spectroscopy with probe sensitivities of ∼1 nm and ∼10 nm, respectively. We obtain direct evidence of metallic Ti 3+ states in the bulk, which get suppressed to give a surface semiconductor, thus indicating a surface-bulk dichotomy. X-ray absorption and high-sensitivity resonant photoemission spectroscopy reveal Ti 3+ electrons at the Fermi level (EF ) and high-spin Co 2+ electrons occurring away from EF . The results show the importance of the charge neutrality condition: Co3+ (VO is oxygen vacancy), which gives rise to the elusive Ti 3d carriers mediating ferromagnetism via the Co 3d -O 2p-Ti 3d exchange interaction pathway of the occupied orbitals.PACS numbers: 79.60.-i, 73.20.-r, 75.50.-y Dilute ferromagnetic oxides have been at the forefront of a paradigm shift in the search for spintronics and magneto-optic device materials [1][2][3][4][5][6]. However, for achieving reliable thin-film device performance, it is necessary to ensure the surface and bulk electronic properties of candidate materials. This is particularly true for high Curie-temperature oxide ferromagnets for spintronics which can be synthesized only in thin film form, such as Co:The main question that still remains enigmatic: What changes drive the long-range coupling of local moments in an insulating parent? The pre-runners, namely, dilute magnetic semiconductors (DMSs) which consisted of magnetic 3d transition metal (TM) ions doped in III-V and II-VI compounds, showed a Curie-temperature (T c ) well-below room temperature e.g. InMnAs, GaMnAs, ZnCrTe, etc [7][8][9]. Theoretical studies of carrier-mediated ferromagnetism played a pivotal role in predicting high-T c ferromagnets in the dilute substitution limit [10]. The spin-charge degrees of freedom and the anisotropic character of the dopant TM d -orbitals results in a directional dependence of exchange energies and T c 's of upto 170 K [11,12]. The limitation of T c 's significantly lower than room temperature motivated studies on alternative parents, like oxides and nitrides. The discovery of ferromagnetism in Co-doped TiO 2 (Co:TiO 2 ), with a T c exceeding 300 K [2], was crucial in expanding the field to oxides, leading to a rapid increase of new materials and phenomena arising from a synergetic marriage of semiconductor physics and strongly correlated systems.From extensive magnetic and transport studies, it is now well-accepted that Co:TiO 2 films grown in a reducing environment or annealed in vacuum result in Co segregation [13,14], while films grown in an oxidizing condition are intrinsically ferromagnetic with high spin Co 2+ [15,16]. While initial x-ray magnetic circular dichroism (XMCD) measurements and annealing in vacuum concluded that the ferromagnetism was extrinsic due to segregated Co metal clusters [14], subsequent XMCD studies showed intrinsic ferromagnetism in Co:TiO 2 grown in oxidizing conditions [17]. A soft xray surface...

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Role of Ti3dCarriers in Mediating the Ferromagnetism ofCo∶TiO2Anatase Thin Films

et al. 2011

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“…The valence band maximum (VBM) of the substrate was determined from the photoemission on-set (that is when the derivative in the spectrum + zero) and is found at 3.0 eV below the Fermi level, in agreement with previous literature. 40,41 Adsorption of pyridines results in a slightly increased intensity between the gap state and the VBM, and also an apparent shift of the leading edge of the valence band toward to the Fermi level. Due to expected spectral contributions from molecular orbitals in the same energy region this shift cannot be directly assigned to a VBM shift.…”

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confidence: 98%

Modification of Charge Transfer and Energy Level Alignment at Organic/TiO₂ Interfaces

Ahmadi

Palmgren

et al. 2009

J. Phys. Chem. C

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Adsorption of titanyl phthalocyanine (TiOPc) on rutile TiO 2 (110) modified by a set of pyridine derivatives (2,2′-bipyridine, 4,4′-bipyridine, and 4-tert-butyl pyridine) has been investigated using synchrotron radiation based X-ray photoelectron spectroscopy (XPS). For the unmodified TiOPc/TiO 2 system, a strong charge transfer is observed from the first layer TiOPc into the substrate, which leads to a molecular layer at the interface with a depleted highest occupied molecular orbital (HOMO). However, precovering the TiO 2 surface with a saturated pyridine monolayer effectively reduce this process and leave the TiOPc in a less perturbed molecular state. Furthermore, the TiOPc HOMO and core levels are observed at different binding energies ranging by 0.3 eV on the three pyridine monolayers, which is ascribed to differences in surface potentials set up by the different pyridine/TiO 2 systems.

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“…1D). In addition, compared with the spectra for r-and h-TiO 2 (110), the dominating features between BEs of~3 and~9.5 eV [primarily O2p-derived (5,7,12,27)] were found to be shifted by~0.4 eV toward E F .…”

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confidence: 99%

The Role of Interstitial Sites in the Ti 3d Defect State in the Band Gap of Titania

Wendt

Sprunger

Lira

et al. 2008

Science

838

111

1,188

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Titanium dioxide (TiO 2 ) has a number of uses in catalysis, photochemistry, and sensing that are linked to the reducibility of the oxide. Usually, bridging oxygen (O br ) vacancies are assumed to cause the Ti 3d defect state in the band gap of rutile TiO 2 (110). From high-resolution scanning tunneling microscopy and photoelectron spectroscopy measurements, we propose that Ti interstitials in the near-surface region may be largely responsible for the defect state in the band gap. We argue that these donor-specific sites play a key role in and may dictate the ensuing surface chemistry, such as providing the electronic charge required for O 2 adsorption and dissociation. Specifically, we identified a second O 2 dissociation channel that occurs within the Ti troughs in addition to the O 2 dissociation channel in O br vacancies. Comprehensive density functional theory calculations support these experimental observations.

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Chiral symmetry restoration in anisotropicQED3

Cited by 33 publications

References 43 publications

Role of Ti3dCarriers in Mediating the Ferromagnetism ofCo∶TiO2Anatase Thin Films

Role of Ti3dCarriers in Mediating the Ferromagnetism ofCo∶TiO2Anatase Thin Films

Modification of Charge Transfer and Energy Level Alignment at Organic/TiO₂ Interfaces

The Role of Interstitial Sites in the Ti 3d Defect State in the Band Gap of Titania

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Chiral symmetry restoration in anisotropicQED3

Cited by 33 publications

References 43 publications

Role of Ti3dCarriers in Mediating the Ferromagnetism ofCo∶TiO2Anatase Thin Films

Role of Ti3dCarriers in Mediating the Ferromagnetism ofCo∶TiO2Anatase Thin Films

Modification of Charge Transfer and Energy Level Alignment at Organic/TiO2 Interfaces

The Role of Interstitial Sites in the Ti 3d Defect State in the Band Gap of Titania

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Modification of Charge Transfer and Energy Level Alignment at Organic/TiO₂ Interfaces