Formation of two-dimensional small polarons at the conducting 
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 interface

Kong, Weilong; Zhou, Jun; Luo, Yong Zheng; Yang, Tong; Wang, Xinbo; Chen, Jingsheng; Rusydi, Andrivo; Feng, Yuan Ping; Yang, Ming

doi:10.1103/physrevb.100.085413

Cited by 10 publications

(8 citation statements)

References 53 publications

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“…That means a large number of electrons at this interface are localized in the form of small polarons, which possibly results in decreased superconducting pairing and lowered superconductivity transition temperature which is not detectable with our STM working at 4.5 K. On the other side, the emergence of interfacial polarons encourages us to compare this interface to similar interfacial superconducting systems like FeSe/STO and LaAlO 3 /SrTiO 3 in which solid evidence has been recently discovered that diffusive large polarons play critical roles in the interfacial conductivity , and even enhanced interfacial superconductivity . A recent theoretical work pointed out that small polarons also present at the LaAlO 3 /SrTiO 3 interface but make insignificant contribution to superconductivity . Theoretically, the long-ranged interaction between electrons and phonons that creates polarons has long been considered favorable for superconducting pairing. , However, whether small polarons help in superconducting pairing is largely unknown.…”

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confidence: 99%

“…17 A recent theoretical work pointed out that small polarons also present at the LaAlO 3 /SrTiO 3 interface but make insignificant contribution to superconductivity. 42 Theoretically, the long-ranged interaction between electrons and phonons that creates polarons has long been considered favorable for superconducting pairing. 43,44 However, whether small polarons help in superconducting pairing is largely unknown.…”

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confidence: 99%

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Interfacial Polarons in van der Waals Heterojunction of Monolayer SnSe₂ on SrTiO₃ (001)

Mao

et al. 2020

Nano Lett.

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Interfacial polarons have been demonstrated to play important roles in heterostructures containing polar substrates. However, most of polarons found so far are diffusive large polarons; the discovery and investigation of small polarons at interfaces are scarce. Herein, we report the emergence of interfacial polarons in monolayer SnSe 2 epitaxially grown on Nb-doped SrTiO 3 (STO) surface using angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy (STM). ARPES spectra taken on this heterointerface reveal a nearly flat in-gap band correlated with a significant charge modulation in real space as observed with STM. An interfacial polaronic model is proposed to ascribe this ingap band to the formation of self-trapped small polarons induced by charge accumulation and electron−phonon coupling at the van der Waals interface of SnSe 2 and STO. Such a mechanism to form interfacial polaron is expected to generally exist in similar van der Waals heterojunctions consisting of layered 2D materials and polar substrates.

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confidence: 99%

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confidence: 99%

Interfacial Polarons in van der Waals Heterojunction of Monolayer SnSe₂ on SrTiO₃ (001)

Mao

et al. 2020

Nano Lett.

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“…The Ti ions attracted around the oxygen vacancies in TiO 6 octahedral forms potential minima which localize electrons and holes to form self‐trapped excitons (STE). [ 29–31 ] We found that the time‐resolved PL at 530 nm (2.34 eV) peak is best fitted by the stretched biexponential decay model while time‐resolved PL at 690 nm (1.8 eV) peak could be fitted well by simple biexponential decay model as shown in Figure S6 in the Supporting Information. This indicates that the 2.34 eV luminescence is excited from electron–hole pair excitonic state while 1.8 eV luminescence could possibly be due to the Ti vacancy defect states.…”

Section: Resultsmentioning

confidence: 88%

Emergent Midgap Excitons in Large‐Size Freestanding 2D Strongly Correlated Perovskite Oxide Films

Zhang

Harsan

Gan

et al. 2021

Advanced Optical Materials

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2D materials exhibit strong excitonic effects due to low dimensionality and enhanced Coulomb interactions, resulting in fascinating many‐particle phenomena like excitons. Though perovskite is a classical type of material hosting abundant correlated electronic phases, freestanding 2D perovskite oxides are not easy to fabricate and yet to be extensively studied. Here the realization of large size (1 × 1 cm2) freestanding perovskite SrTiO3 films, which show unexpected excitonic photoluminescence (PL) spectra and carrier dynamics, is reported. Two pronounced broad PL peaks emerge in 2D freestanding SrTiO3 films at 2.34–2.4 and 1.8–1.9 eV, of which the 2.34–2.4 eV emission originates from self‐trapped excitons localized within TiO6 octahedra, and the 1.8–1.9 eV peak from Ti vacancies. The time‐resolved PL shows a remarkable enhancement of nonradiative Auger recombination through three‐particle process, in which electron–hole excitons transfer their kinetic energy to other free electrons or holes. The results demonstrate unique excitonic properties in 2D perovskite SrTiO3 films and unravel their potential for high‐performance optoelectronic devices.

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“…In summary, we have shown the emergence of coexisting charge density waves, polarons, and bipolarons originating from the intrinsic uncompensated charge of the polar TaO 2 -terminated KTaO 3 (001) surface. We have obtained a direct, real-space view of these states, in contrast to similar phenomena at interfaces of heterostructured materials 17 , 45 – 47 , where the charge distribution is not directly accessible. The competition between charge-ordering (CDW and (bi)polaronic states) and homogeneous distribution (2DEG) arises from the contrasting action of spatially extended 5 d orbitals of Ta (favoring charge delocalization) and strong electronic correlation (favoring charge localization).…”

Section: Resultsmentioning

confidence: 99%

Competing electronic states emerging on polar surfaces

et al. 2022

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Excess charge on polar surfaces of ionic compounds is commonly described by the two-dimensional electron gas (2DEG) model, a homogeneous distribution of charge, spatially-confined in a few atomic layers. Here, by combining scanning probe microscopy with density functional theory calculations, we show that excess charge on the polar TaO2 termination of KTaO3(001) forms more complex electronic states with different degrees of spatial and electronic localization: charge density waves (CDW) coexist with strongly-localized electron polarons and bipolarons. These surface electronic reconstructions, originating from the combined action of electron-lattice interaction and electronic correlation, are energetically more favorable than the 2DEG solution. They exhibit distinct spectroscopy signals and impact on the surface properties, as manifested by a local suppression of ferroelectric distortions.

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Formation of two-dimensional small polarons at the conducting LaAlO3/SrTiO3 interface

Cited by 10 publications

References 53 publications

Interfacial Polarons in van der Waals Heterojunction of Monolayer SnSe₂ on SrTiO₃ (001)

Interfacial Polarons in van der Waals Heterojunction of Monolayer SnSe₂ on SrTiO₃ (001)

Emergent Midgap Excitons in Large‐Size Freestanding 2D Strongly Correlated Perovskite Oxide Films

Competing electronic states emerging on polar surfaces

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Formation of two-dimensional small polarons at the conducting LaAlO3/SrTiO3 interface

Cited by 10 publications

References 53 publications

Interfacial Polarons in van der Waals Heterojunction of Monolayer SnSe2 on SrTiO3 (001)

Interfacial Polarons in van der Waals Heterojunction of Monolayer SnSe2 on SrTiO3 (001)

Emergent Midgap Excitons in Large‐Size Freestanding 2D Strongly Correlated Perovskite Oxide Films

Competing electronic states emerging on polar surfaces

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Product

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Interfacial Polarons in van der Waals Heterojunction of Monolayer SnSe₂ on SrTiO₃ (001)

Interfacial Polarons in van der Waals Heterojunction of Monolayer SnSe₂ on SrTiO₃ (001)