Determination of the Mott-Hubbard gap in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>GdTiO</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:math>

Bjaalie, Lars; Verma, Amit; Himmetoḡlu, Burak; Janotti, Anderson; Raghavan, Santosh; Protasenko, Vladimir; Steenbergen, Elizabeth H.; Jena, Debdeep; Stemmer, Susanne; Walle, Chris G. Van de

doi:10.1103/physrevb.92.085111

Cited by 18 publications

(11 citation statements)

References 34 publications

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“…GTO assumes a distorted orthorhombic (P nmb) structure, with a 20-atom unit cell. The calculated lattice parameters and bond angles are in good agreement with experiment, and the value of the energy gap is 2.02 eV, in agreement with optical measurements [21]. Wavefunctions were expanded in a plane-wave basis set with a 400 eV energy cutoff, and the (1/4, 1/4, 1/4) special k-point was used for integrations over the Brillouin zone.…”

Section: A Density Functional Theorysupporting

confidence: 80%

Point defects, impurities, and small hole polarons inGdTiO3

et al. 2016

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The electronic structure of native defects and impurities in GdTiO3, a rare-earth titanate Mott insulator, is studied using density functional theory with a hybrid functional. Among native defects, the cation vacancies have the lowest formation energies in oxygen-rich conditions and oxygen vacancies have the lowest formation energy in oxygen-poor conditions. Among the impurities, Sr Gd , Hi and CO have low formation energies. A common feature of the native defects and impurities is that they lead to the formation of small hole polarons, which explains the frequent observation of p-type hopping conductivity in the rare-earth titanates. These small hole polarons also lead to optical absorption and act as electron traps in devices.

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Section: A Density Functional Theorysupporting

confidence: 80%

Point defects, impurities, and small hole polarons inGdTiO3

et al. 2016

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“…We can check the role of the effective Jahn-Teller motion in our calculations by analyzing in details the electronic and magnetic properties of YTiO 3 and LaTiO 3 . We observe that both YTiO 3 and LaTiO 3 are insulators in our simulations with band gaps of 1.04 and 0.94 eV respectively, compatible with experimental reports on differentq titanates [33][34][35][36][37]. Our computed magnetic moments on Ti 3+ are evaluated around 0.94 µ B and 0.84 µ B for YTiO 3 and LaTiO 3 respectively and agree with experiments although the latter value is slightly overestimated [38,39].…”

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confidence: 88%

Origin of the orbital and spin ordering in rare-earth titanates

et al. 2017

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Rare-earth titanates RTiO3 are Mott insulators displaying a rich physical behavior, featuring most notably orbital and spin orders in their ground state. The origin of their ferromagnetic to antiferromagnetic transition as a function of the size of the rare-earth however remains debated. Here we show on the basis of symmetry analysis and first-principles calculations that although rare-earth titanates are nominally Jahn-Teller active, the Jahn-Teller distortion is negligible and irrelevant for the description of the ground state properties. At the same time, we demonstrate that the combination of two antipolar motions produces an effective Jahn-Teller-like motion which is the key of the varying spin-orbital orders appearing in titanates. Thus, titanates are prototypical examples illustrating how a subtle interplay between several lattice distortions commonly appearing in perovskites can produce orbital orderings and insulating phases irrespective of proper Jahn-Teller motions.ABO 3 oxide perovskites, with partly filled d states on the B site, exhibit a rich physical behavior originating from the intimate coupling between structural, electronic (charge and orbital) and magnetic degrees of freedom [1]. Typical examples are the rare-earth vanadateselectronic configuration on V 3+ ions) that exhibit two different spin and orbital orders yielding distinct symmetries for the ground state at low temperature [2,3]. With the electronic degeneracy of Ti 3+ -3d 1 -t 1 2g configuration -, rare-earth titanates R 3+ Ti 3+ O 3 are often expected to be another text book example of such a subtle interplay between orbital and spin orders.Rare-earth titanates are Mott insulators, which according to their small tolerance factor, adopt a common orthorhombic P bnm structure characterized by large oxygen cage rotations [4][5][6], i.e a − a − c + antiferrodistortive motions in Glazer's notations [7]. They also all undergo a magnetic phase transition to either a ferromagnetic (FM) ordering for small R= Lu-Gd+Y or a G-type antiferromagnetic (G-AFM) ordering for large R= SmLa [6,8,9].The nature of the very peculiar FM to G-AFM transition as a function of the rare-earth size is however puzzling and controversial [9]. On one hand, Ti 3+ is nominally a Jahn-Teller (JT) active ion and the JT distortion is commonly proposed as a key ingredient to explain the transition [10,11]. However, while such a distortion could be compatible with the ferromagnetic phase [12,13], it cannot provide a satisfying explanation for the purely antiferromagnetic phase [10]. On the other hand, some other works have proposed that the JT distortion is neither responsible for the insulating phase of these materials nor for the observed orbital orders [14,15].Instead, Mochizuki et al have suggested that specific orbital-orderings for the FM and AFM phases are triggered by the crystal field produced by the rareearth [13,16], with a potential competition with the JT distortion [11]. This latter model ultimately results in combinations of the three t 2g orbitals [9,13,16,...

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“…Apart from weak thermal broadening with increasing temperature, the peak at 2 eV is nearly temperature independent. While early studies of GTO measured a MH gap of 0.2 -0.7 eV [28], more recent photoluminescence and DFT/DFT+U results place the gap closer to 1.8 -2 eV [29]. The small peak in the optical conductivity spectrum at 2 eV measured here supports these recent findings.…”

Section: Resultssupporting

confidence: 80%

Magneto-Elastic Coupling to Coherent Acoustic Phonon Modes in Ferrimagnetic Insulator GdTiO$_3$

Lovinger,

Zoghlin,

Kissin

et al. 2020

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In this work we investigate single crystal GdTiO3, a promising candidate material for Floquet engineering and magnetic control, using ultrafast optical pump-probe reflectivity and magneto-optical Kerr spectroscopy. GdTiO3 is a Mott-Hubbard insulator with a ferrimagnetic and orbitally ordered ground state (TC = 32 K). We observe multiple signatures of the magnetic phase transition in the photoinduced reflectivity signal, in response to above band-gap 660 nm excitation. Magnetic dynamics measured via Kerr spectroscopy reveal optical perturbation of the ferrimagnetic order on spin-lattice coupling timescales, highlighting the competition between the Gd 3+ and Ti 3+ magnetic sub-lattices. Furthermore, a strong coherent oscillation is present in the reflection and Kerr dynamics, attributable to an acoustic strain wave launched by the pump pulse. The amplitude of this acoustic mode is highly dependent on the magnetic order of the system, growing sharply in magnitude at TC, indicative of strong magneto-elastic coupling. The driving mechanism, involving strain-induced modification of the magnetic exchange interaction, implies an indirect method of coupling light to the magnetic degrees of freedom and emphasizes the potential of GdTiO3 as a tunable quantum material.

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Determination of the Mott-Hubbard gap inGdTiO3

Cited by 18 publications

References 34 publications

Point defects, impurities, and small hole polarons inGdTiO3

Point defects, impurities, and small hole polarons inGdTiO3

Origin of the orbital and spin ordering in rare-earth titanates

Magneto-Elastic Coupling to Coherent Acoustic Phonon Modes in Ferrimagnetic Insulator GdTiO$_3$

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