Two-channel model for optical conductivity of high-mobility organic crystals

Candia, A. de; Filippis, G. De; Cangemi, L. M.; Mishchenko, A. S.; Nagaosa, Naoto; Cataudella, V.

doi:10.1209/0295-5075/125/47002

Cited by 4 publications

(4 citation statements)

References 36 publications

(69 reference statements)

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“…Therefore, the defects affect μ e not only through their concentration but also through the EPI-mediated electron-defect scattering strength which, in turn, increases with the defect concentration. This cumulative effect results in a steep non-linear change of μ e as a function of the latter, predicted within the mean-field approximation already four decades ago and later reproduced by approximation-free diagrammatic Monte Carlo calculations. − This effect is likely to be at play to boost μ e as the effective V O concentration experienced by the d xz / d yz electrons in GAO/STO decreases thanks to the band-order anomaly. Indeed, this decrease is evident from our analysis of the QP peak width in Figure b.…”

Section: Discussionmentioning

confidence: 89%

“…This cumulative effect results in a steep non-linear change of µ e as a function of the latter, predicted within the mean-field approximation already four decades ago 49 and later reproduced by approximation-free Diagrammatic Monte Carlo calculations. [50][51][52] This effect is likely to be at play to boost µ e with decrease of the effective V O concentration experienced by the d xz/yz electrons in GAO/STO thanks to the band-order anomaly.…”

Section: Effects Of the Epimentioning

confidence: 99%

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Band-Order Anomaly at the γ-Al₂O₃/SrTiO₃ Interface Drives the Electron-Mobility Boost

et al. 2021

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Rich functionalities of transition-metal oxides and their interfaces bear an enormous technological potential. Its realization in practical devices requires, however, a significant improvement of yet relatively low electron mobility in oxide materials. Recently, a mobility boost of about two orders of magnitude has been demonstrated at the spinel/perovskite γ-Al 2 O 3 /SrTiO 3 interface compared to the paradigm perovskite/perovskite LaAlO 3 /SrTiO 3 . We explore the fundamental physics behind this phenomenon from direct measurements of the momentum-resolved electronic structure of this interface using resonant soft-X-ray angle-resolved photoemission. We find an anomaly in orbital ordering of the mobile electrons in γ-Al 2 O 3 /SrTiO 3 which depopulates electron states in the top STO layer. This rearrangement of the mobile electron system pushes the electron density away from the interface that reduces its overlap with the interfacial defects and weakens the electron-phonon interaction, both effects contributing to the mobility boost. A crystal-field analysis shows that the band order alters owing to the symmetry breaking between the spinel γ-Al 2 O 3 and perovskite SrTiO 3 . The band-order engineering exploiting the fundamental symmetry properties emerges as another route to boost the performance of oxide devices.

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Section: Discussionmentioning

confidence: 89%

Section: Effects Of the Epimentioning

confidence: 99%

Band-Order Anomaly at the γ-Al₂O₃/SrTiO₃ Interface Drives the Electron-Mobility Boost

et al. 2021

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“…Slowly fluctuating dynamic stripes are essentially static at the energy scale of midinfrared conductivity (order of 0.5 eV) and play a role of an impurity potential. The optical response of such trapped carriers is significant only at high energies 46 . However, midinfrared optical conductivity in the high-temperature dynamic stripe phase is characterized by a broad absorption band extending all the way to zero energy.…”

Section: Discussionmentioning

confidence: 99%

Giant electron–phonon coupling of the breathing plane oxygen phonons in the dynamic stripe phase of $$\hbox {La}_{1.67}\hbox {Sr}_{0.33}\hbox {NiO}_4$$

Merritt

Christianson

Banerjee

et al. 2020

Sci Rep

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Doped antiferromagnets host a vast array of physical properties and learning how to control them is one of the biggest challenges of condensed matter physics. La 1.67 Sr 0.33 NiO 4 (LSno) is a classic example of such a material. At low temperatures holes introduced via substitution of La by Sr segregate into lines to form boundaries between magnetically ordered domains in the form of stripes. the stripes become dynamic at high temperatures, but LSno remains insulating presumably because an interplay between magnetic correlations and electron-phonon coupling localizes charge carriers. Magnetic degrees of freedom have been extensively investigated in this system, but phonons are almost completely unexplored. We searched for electron-phonon anomalies in LSno by inelastic neutron scattering. Giant renormalization of plane ni-o bond-stretching modes that modulate the volume around ni appears on entering the dynamic charge stripe phase. other phonons are a lot less sensitive to stripe melting. Dramatic overdamping of the breathing modes indicates that dynamic stripe phase may host small polarons. We argue that this feature sets electron-phonon coupling in nickelates apart from that in cuprates where breathing phonons are not overdamped and point out remarkable similarities with the colossal magnetoresistance manganites. Mott insulators should become metallic when extra charge carriers are introduced by doping. However, many of them remain insulating or become very poor metals with large electrical resistivity and incoherent or diffusive transport 1,2. This behavior is particularly common in transition metal oxides that have the potential to realize novel electronic phases with interesting and exotic properties from nontrivial topologies to superconductivity 3. Poor electrical conductivity is typically associated with charge carrier localization arising from interactions between different quasiparticles 4. Learning how to control these interactions is challenging, especially in the presence of strong electron-electron correlations. Electron-phonon coupling is often involved in localization of charge carriers in crystalline materials. For example, in the case of polaron formation, the carriers locally distort the atomic lattice and the distortions trap the carriers when the electron-phonon coupling strength is large enough 5. A detailed understanding of both electronic and phonon channels is necessary to accurately account for such phenomena. A lot of research focused on the former 4,6 , but the latter is poorly characterized in many interesting materials. Time-of-flight neutron scattering instruments can map the phonon spectra over hundreds of Brillouin zones, but comprehensive analysis of these datasets is extremely difficult and time-consuming. For example, small peaks in the background can be assigned to phonons. A broad peak may arise from a superposition of two or more closely-spaced peaks. Some phonons can be overlooked since most of them have appreciable structure factor only in a few zones, etc. Recently we deve...

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“…Slowly fluctuating dynamic stripes are essentially static at the energy scale of midinfrared conductivity (order of 0.5eV) and play a role of an impurity potential. The optical response of such trapped carriers is significant only at high energies [49]. However, midinfrared optical conductivity in the high-temperature dynamic stripe phase is characterized by a broad absorption band extending all the way to zero energy.…”

Section: Discussionmentioning

confidence: 99%

Giant electron-phonon coupling of the breathing plane oxygen phonons in the dynamic stripe phase of La$_{1.67}$Sr$_{0.33}$NiO$_4$

Merritt,

Christianson,

Banerjee

et al. 2020

Preprint

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Doped antiferromagnets host a vast array of physical properties and learning how to control them is one of the biggest challenges of condensed matter physics. La1.7Sr0.3NiO4 (LSNO) is a classic example of such a material. At low temperatures holes introduced via substitution of La by Sr segregate into lines to form boundaries between magnetically ordered domains in the form of stripes. The stripes become dynamic at high temperatures, but LSNO remains insulating presumably because an interplay between magnetic correlations and electron-phonon coupling localizes charge carriers. Magnetic degrees of freedom have been extensively investigated in this system, but phonons are almost completely unexplored. We searched for electron-phonon anomalies in LSNO by inelastic neutron scattering. Giant renormalization of plane Ni-O bond-stretching modes that modulate the volume around Ni appears on entering the dynamic charge stripe phase. Other phonons are a lot less sensitive to stripe melting. Dramatic overdamping of the breathing modes indicates that dynamic stripe phase may host small polarons. We argue that this feature sets electron-phonon coupling in nickelates apart from that in cuprates where breathing phonons are not overdamped and point out remarkable similarities with the colossal magnetoresistance (CMR) manganites.

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Two-channel model for optical conductivity of high-mobility organic crystals

Cited by 4 publications

References 36 publications

Band-Order Anomaly at the γ-Al₂O₃/SrTiO₃ Interface Drives the Electron-Mobility Boost

Band-Order Anomaly at the γ-Al₂O₃/SrTiO₃ Interface Drives the Electron-Mobility Boost

Giant electron–phonon coupling of the breathing plane oxygen phonons in the dynamic stripe phase of $$\hbox {La}_{1.67}\hbox {Sr}_{0.33}\hbox {NiO}_4$$

Giant electron-phonon coupling of the breathing plane oxygen phonons in the dynamic stripe phase of La$_{1.67}$Sr$_{0.33}$NiO$_4$

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Two-channel model for optical conductivity of high-mobility organic crystals

Cited by 4 publications

References 36 publications

Band-Order Anomaly at the γ-Al2O3/SrTiO3 Interface Drives the Electron-Mobility Boost

Band-Order Anomaly at the γ-Al2O3/SrTiO3 Interface Drives the Electron-Mobility Boost

Giant electron–phonon coupling of the breathing plane oxygen phonons in the dynamic stripe phase of $$\hbox {La}_{1.67}\hbox {Sr}_{0.33}\hbox {NiO}_4$$

Giant electron-phonon coupling of the breathing plane oxygen phonons in the dynamic stripe phase of La$_{1.67}$Sr$_{0.33}$NiO$_4$

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Band-Order Anomaly at the γ-Al₂O₃/SrTiO₃ Interface Drives the Electron-Mobility Boost

Band-Order Anomaly at the γ-Al₂O₃/SrTiO₃ Interface Drives the Electron-Mobility Boost