First-principles studies of lone-pair-induced distortions in epitaxial phases of perovskite<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>SnTiO</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>PbTiO</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:math>

Pitike, Krishna Chaitanya; Parker, William R.; Louis, Lydie; Nakhmanson, Serge

doi:10.1103/physrevb.91.035112

Cited by 33 publications

(20 citation statements)

References 64 publications

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“…The hybridization also causes the asymmetric ELF lobes near at the Pb sites as shown in Fig. 5 (c) and (d), which is a characteristic of the lone-pair mechanism 49,54 .…”

Section: Increasing Of the A-site Instabilitymentioning

confidence: 91%

Persistence of polar distortion with electron doping in lone-pair driven ferroelectrics

Jin

2016

Phys. Rev. B

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Free electrons can screen out long-range Coulomb interaction and destroy the polar distortion in some ferroelectric materials, whereas the coexistence of polar distortion and metallicity were found in several non-centralsymmetric metals (NCSMs). Therefore, the mechanisms and designing of NCSMs have attracted great interests. In this work, by first-principles calculation, we found the polar distortion in the lone-pair driven ferroelectric material PbTiO3 can not only persist, but also increase with electron doping. We further analyzed the mechanisms of the persisting of the polar distortion. We found that the Ti site polar instability is suppressed but the Pb site polar instability is intact with the electron doping. The Pb-site instability is due to the lone-pair mechanism which can be viewed as a pseudo-Jahn-Teller effect, a mix of the ground state and the excited state by ion displacement from the central symmetric position. The lone-pair mechanism is not strongly affected by the electron doping because neither the ground state nor the excited state involved is at the Fermi energy. The enhancement of the polar distortion is related to the increasing of the Ti ion size by doping. These results show that the long-pair stereoactive ions can be used for designing NCSMs.Although the NCSM structures are no longer suitable for the usage as ferroelectric materials because of the metallicity, other interesting properties are found in NCSMs, like the unconventional optical responses 15,16 , magnetoelectricity 17 , superconductivity 18 , and thermoelectricity 13 . A deeper understanding of the mechanisms of NCSM could help finding new NCSMs. The purpose of this work is to seek a possible mechanism of NCSMs so new NCSMs can be found or designed.In this work, by studying the polar distortion in electrondoped PbTiO 3 , we show that the lone-pair driven polar distortion is compatible with metallicity. The lone pair mechanism for the polar distortion in non-doped PbTiO 3 has been long studied [19][20][21][22] . In PbTiO 3 , the hybridization between the Pb (6s, 6p) bands and O 2p bands reduces the short-range repulsion, resulting in a large polar distortion, which is often referred as lone-pair driven ferroelectricity. The lone-pair driven ferroelectricity can be interpreted as the result of the Pseudo-Jahn-Teller effect (PJTE). 23-26 which is local. Therefore, it is possible that the lone pair mechanism can still drive the polar distortion even if the long-range interaction is screened. We found that the polar distortion in PbTiO 3 not only persists but also is enhanced with the electron doping. Then by analyzing the evolution of the phonon and the force constant matrices (FCM's), we found that the A-site instability, which is caused by the lone-pair mechanism, is responsible for the persisting of the polar distortion, because the electronic states involved are far away from the Fermi energy. We showed that enhancement of the polar distortion is related to the increasing of the Pb-O distance. We discussed the generalizability...

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“…The hybridization also causes the asymmetric ELF lobes near at the Pb sites as shown in Fig. 5 (c) and (d), which is a characteristic of the lone-pair mechanism 49,54 .…”

Section: Increasing Of the A-site Instabilitymentioning

confidence: 91%

Persistence of polar distortion with electron doping in lone-pair driven ferroelectrics

Jin

2016

Phys. Rev. B

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“…More importantly, Sn is isoelectronic to Pb and environmentally benign. Thus, SnTiO 3 has attracted lots of theoretical attention for its possible physical properties without doping [21,[24][25][26][27]. We will present here that P 4mm SnTiO 3 shows a great compatibility with polar distortions and mobile carriers as PbTiO 3 with electrostatic doping.…”

Section: Introductionmentioning

confidence: 80%

“…Although doping in BaTiO 3 has been tentatively studied theoretically [14,15] and explored experimentally [16][17][18][19], the screening of long-range Coulomb interactions has been proven to suppress polar distortions with doping [14,15]. To achieve "polar metals," doping in lone-pair ferroelectrics [20][21][22] should be a promising approach, which has been scarcely studied so far. Very recently, we reported a theoretical research on the electron doping effect in lone-pair ferroelectrics PbTiO 3 [22], predicting that electron doping even enhances polar distortion.…”

Section: Introductionmentioning

confidence: 99%

Polar instability under electrostatic doping in tetragonal SnTiO3

Jin

2017

Phys. Rev. B

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How to make the metallicity compatible with a polar structure for forming a "polar metal" has been an interesting and important topic since the polar structure was discovered in metallic LiOsO 3. Here, we present robust polar instability under electrostatic doping in tetragonal SnTiO 3 based on our first-principles calculations. The mechanism for polar distortion surviving free carriers is investigated from the "weak-coupling" perspective. The contributions of different interactions between two polar modes in a "ferroelectric" phase transition are also studied. We found that the short-range interaction contributes the most for lowering the total energy during the ferroelectricphase transition. Moreover, the dipole-dipole interaction between two polar modes of oxygen atoms provides the largest energy gain among local interactions, which cannot be screened out by doping. We propose that the promising candidates for noncentrosymmetric metals obtained by doping are ferroelectrics with bonding states responsible for polar distortions away from the Fermi level. We believe that this mechanism sheds light on a method to obtain noncentrosymmetric metals from a large amount of ferroelectric perovskite oxides by doping.

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“…This lone-pair-driven persistence of polarity has also been found in BFO 37) . It may also be applicable to other lone-pair-driven ferroelectrics, such as PbVO3 65) , SnTiO3 66) and BiMnO3 67) .…”

Section: Batio 3 and Other Perovskite Oxidesmentioning

confidence: 99%

Review on ferroelectric/polar metals

Zhou

Ariando

2020

Jpn. J. Appl. Phys.

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The possibility of reconciliation between seemingly mutually exclusive properties in one system can not only lead to theoretical breakthroughs but also potential novel applications. The research on the coexistence of two purportedly contra-indicated properties, ferroelectricity/polarity and conductivity, proposed by Anderson and Blount over 50 years ago was recently revitalized by the discovery of the first unambiguous polar metal LiOsO 3 and further fueled by the demonstration of the first switchable ferroelectric metal WTe 2 . In this review, we first discuss the reasons why the coexistence of ferroelectricity/polarity and conductivity have been deemed incompatible, followed by a review on the history of ferroelectric/polar metals. Secondly, we review the important milestones along with the corresponding mechanisms for the ferroelectric/polar metallic phases in these materials.Thirdly, we summarize the design approaches for ferroelectric/polar metals. Finally, we discuss the future prospects and potential applications of ferroelectric/polar metals.

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First-principles studies of lone-pair-induced distortions in epitaxial phases of perovskiteSnTiO3andPbTiO3

Cited by 33 publications

References 64 publications

Persistence of polar distortion with electron doping in lone-pair driven ferroelectrics

Persistence of polar distortion with electron doping in lone-pair driven ferroelectrics

Polar instability under electrostatic doping in tetragonal SnTiO3

Review on ferroelectric/polar metals

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