<i>h</i>-ErMnO<sub>3</sub> absorbance, reflectivity and, emissivity in the THz to mid-infrared from 2 K to 1700 K : Carrier screening, Fröhlich resonance, small polarons, and bipolarons

We report the temperature dependent THz to mid-infrared response of hexagonal-ErMnO<sub>3</sub> using absorption, reflectivity, and emissivity techniques from 2 K to 1700 K. At low temperatures, lowest frequency vibrational modes which extend up the lock-in ferroelectric temperature, coe...

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Autores principales: Massa, Néstor Emilio, del Campo, Leire, Holldack, Karsten, Canizares, Aurélien, Phuoc, Vinh Ta, Kayser, Paula, Alonso, José Antonio
Formato: Articulo Preprint
Lenguaje:Inglés
Publicado: 2020
Materias:
Física
Ciencias Exactas
Fröhlich resonance
polarons
bipolarons
Phonon interactions
Acceso en línea:http://sedici.unlp.edu.ar/handle/10915/125735
Aporte de:
SEDICI (UNLP) de Universidad Nacional de La Plata
id I19-R120-10915-125735
record_format dspace
institution Universidad Nacional de La Plata
institution_str I-19
repository_str R-120
collection SEDICI (UNLP)
language Inglés
topic Física
Ciencias Exactas
Fröhlich resonance
polarons
bipolarons
Phonon interactions
spellingShingle Física
Ciencias Exactas
Fröhlich resonance
polarons
bipolarons
Phonon interactions
Massa, Néstor Emilio
del Campo, Leire
Holldack, Karsten
Canizares, Aurélien
Phuoc, Vinh Ta
Kayser, Paula
Alonso, José Antonio
<i>h</i>-ErMnO<sub>3</sub> absorbance, reflectivity and, emissivity in the THz to mid-infrared from 2 K to 1700 K : Carrier screening, Fröhlich resonance, small polarons, and bipolarons
topic_facet Física
Ciencias Exactas
Fröhlich resonance
polarons
bipolarons
Phonon interactions
description We report the temperature dependent THz to mid-infrared response of hexagonal-ErMnO<sub>3</sub> using absorption, reflectivity, and emissivity techniques from 2 K to 1700 K. At low temperatures, lowest frequency vibrational modes which extend up the lock-in ferroelectric temperature, coexist with paramagnon excitations and are associated with well-defined crystal field Rare Earth pure magnetic replicas in an intriguing phonon-magnetic convergence enhancing the multiferroic character of <i>h</i>-ErMnO<sub>3</sub>. Increasing the temperature, a number of vibrational bands close to the space group predicted undergo profile broadening and softening. In particular, a distinctive set of bands in the 288-329 cm<sup>-1</sup> (300 K) range has a component whose profile is carrier screened becoming nearly fully blurred in the intermediate phase between ~830 K and ~1500 K. Below TC ~830 K this asymmetric band, having one component still partially screened, further splits as spin phonon interaction and the tripling of the unit cell takes place revealing at TN ~79 K a delicate balance of long- and short-range interactions. Ambient Raman scattering brings up evidence of a Fröhlich resonance due to Coulomb interactions between carriers and the macroscopic field linked to the corresponding longitudinal optical phonon mode. We found it is dynamically correlated to the hexagonal c-axis negative thermal expansion. Quantitative analyses of the mid-infrared (MIR) optical conductivity show that also plays a role in small polarons and mediates in high temperature bipolarones. Bipolaron profiles at high temperatures change as the sample opacity increases when at ~900 K straight stripes turn curly toward complex vortex-antivortex domain patterns in the paraelectric phase. At still higher temperatures a low frequency Drude contribution is triggered by electron hopping signaling an insulator-metal phase transition at ~1600 K while the MIR response suggests coexistence between single small polarons and bipolarons. On closing, we draw a parallel with improper ferroelectrics sustaining a lattice incommensurate intermediate phase and unit cell tripling. We argue that in the <i>h</i>-ErMnO<sub>3</sub> (R=Rare Earth, Y) family of compounds the intermediate phase be considered incommensurate with onset at TINC ~1500 K and ferroelectric lock-in at TC ~830 K delimiting this regime in <i>h</i>-ErMnO<sub>3</sub>.
format Articulo
Preprint
author Massa, Néstor Emilio
del Campo, Leire
Holldack, Karsten
Canizares, Aurélien
Phuoc, Vinh Ta
Kayser, Paula
Alonso, José Antonio
author_facet Massa, Néstor Emilio
del Campo, Leire
Holldack, Karsten
Canizares, Aurélien
Phuoc, Vinh Ta
Kayser, Paula
Alonso, José Antonio
author_sort Massa, Néstor Emilio
title <i>h</i>-ErMnO<sub>3</sub> absorbance, reflectivity and, emissivity in the THz to mid-infrared from 2 K to 1700 K : Carrier screening, Fröhlich resonance, small polarons, and bipolarons
title_short <i>h</i>-ErMnO<sub>3</sub> absorbance, reflectivity and, emissivity in the THz to mid-infrared from 2 K to 1700 K : Carrier screening, Fröhlich resonance, small polarons, and bipolarons
title_full <i>h</i>-ErMnO<sub>3</sub> absorbance, reflectivity and, emissivity in the THz to mid-infrared from 2 K to 1700 K : Carrier screening, Fröhlich resonance, small polarons, and bipolarons
title_fullStr <i>h</i>-ErMnO<sub>3</sub> absorbance, reflectivity and, emissivity in the THz to mid-infrared from 2 K to 1700 K : Carrier screening, Fröhlich resonance, small polarons, and bipolarons
title_full_unstemmed <i>h</i>-ErMnO<sub>3</sub> absorbance, reflectivity and, emissivity in the THz to mid-infrared from 2 K to 1700 K : Carrier screening, Fröhlich resonance, small polarons, and bipolarons
title_sort <i>h</i>-ermno<sub>3</sub> absorbance, reflectivity and, emissivity in the thz to mid-infrared from 2 k to 1700 k : carrier screening, fröhlich resonance, small polarons, and bipolarons
publishDate 2020
url http://sedici.unlp.edu.ar/handle/10915/125735
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