{"id":{"repo_id":"potsdam-diss","oai_identifier":"oai:kobv.de-opus4-uni-potsdam:7762"},"canonical_url":"https://search.dev.ndltd.org/etd/potsdam-diss/oai:kobv.de-opus4-uni-potsdam:7762","repository":{"repo_id":"potsdam-diss","name":"Universität Potsdam - Diss","base_url":"https://publishup.uni-potsdam.de/opus4-ubp/oai"},"display":{"title":"Spectroscopic perspectives on ultrafast coupling phenomena in perovskite oxides","abstract":"In this thesis, I study ultrafast dynamics in perovskite oxides using time resolved broadband spectroscopy. I focus on the observation of coherent phonon propagation by time resolved Brillouin scattering: following the excition of metal transducer films with a femtosecond infrared pump pulse, coherent phonon dynamics in the GHz frequency range are triggered. Their propagation is monitored using a delayed white light probe pulse. The technique is illustrated on various thin films and multilayered samples. I apply the technique to investigate the linear and nonlinear acoustic response in bulk SrTiO_3, which displays a ferroelastic phase transition from a cubic to a tetragonal structural phase at T_a=105 K. In the linear regime, I observe a coupling of the observed acoustic phonon mode to the softening optic modes describing the phase transition. In the nonlinear regime, I find a giant slowing down of the sound velocity in the low temperature phase that is only observable for a strain amplitude exceeding the tetragonality of the material. It is attributed to a coupling of the high frequency phonons to ferroelastic domain walls in the material. I propose a new mechanism for the coupling of strain waves to the domain walls that is only effective for high amplitude strain. A detailed study of the phonon attenuation across a wide temperature range shows that the phonon attenuation at low temperatures is influenced by the domain configuration, which is determined by interface strain. Preliminary measurements on magnetic-ferroelectric multilayers reveal that the excitation fluence needs to be carefully controlled when dynamics at phase transitions are studied.","abstract_html":"In this thesis, I study ultrafast dynamics in perovskite oxides using time resolved broadband spectroscopy. I focus on the observation of coherent phonon propagation by time resolved Brillouin scattering: following the excition of metal transducer films with a femtosecond infrared pump pulse, coherent phonon dynamics in the GHz frequency range are triggered. Their propagation is monitored using a delayed white light probe pulse. The technique is illustrated on various thin films and multilayered samples. I apply the technique to investigate the linear and nonlinear acoustic response in bulk SrTiO_3, which displays a ferroelastic phase transition from a cubic to a tetragonal structural phase at T_a=105 K. In the linear regime, I observe a coupling of the observed acoustic phonon mode to the softening optic modes describing the phase transition. In the nonlinear regime, I find a giant slowing down of the sound velocity in the low temperature phase that is only observable for a strain amplitude exceeding the tetragonality of the material. It is attributed to a coupling of the high frequency phonons to ferroelastic domain walls in the material. I propose a new mechanism for the coupling of strain waves to the domain walls that is only effective for high amplitude strain. A detailed study of the phonon attenuation across a wide temperature range shows that the phonon attenuation at low temperatures is influenced by the domain configuration, which is determined by interface strain. Preliminary measurements on magnetic-ferroelectric multilayers reveal that the excitation fluence needs to be carefully controlled when dynamics at phase transitions are studied.","abstract_has_math":false,"creators":["Maerten, Lena"],"institution":"Universität Potsdam","degree_name":null,"degree_level":"thesis.doctoral","degree_discipline":null,"degree_department":null,"school":null,"contributors":["Bargheer, Matias"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2015,"date_issued":"2015-04-30","date_published":"2015-04-30","updated_at":"2026-07-24T03:51:50Z","subjects":["coherent phonons","phonon dynamics","time resolved","Brillouin scattering","perovskite oxides","optical spectroscopy","hypersound propagation","phonon damping","domain wall motion","phonon backfolding","superlattice dispersion","kohärente Phononen","Phononen Dynamik","zeitaufgelöst","Brillouin Streuung","Perowskit-Oxide","optische Spektroskopie","Hyperschall Propagation","Phononen Dämpfung","Domänenwandbewegung","Phononen Rückfaltung","Übergitter Dispersion"],"languages":[],"rights":["Keine öffentliche Lizenz: Unter Urheberrechtsschutz"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://publishup.uni-potsdam.de/frontdoor/index/index/docId/7762","outbound_label":"Repository record","outbound_source":"source_url"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Bargheer, Matias"]},{"key":"dc:creator","label":"Author","values":["Maerten, Lena"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:publisher","label":"Institution","values":["Universität Potsdam"]},{"key":"dc:type","label":"Dc Type","values":["doctoralThesis"]},{"key":"thesis:degree_level","label":"Degree Level","values":["thesis.doctoral"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["Universität Potsdam"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["coherent phonons","phonon dynamics","time resolved","Brillouin scattering","perovskite oxides","optical spectroscopy","hypersound propagation","phonon damping","domain wall motion","phonon backfolding","superlattice dispersion","kohärente Phononen","Phononen Dynamik","zeitaufgelöst","Brillouin Streuung","Perowskit-Oxide","optische Spektroskopie","Hyperschall Propagation","Phononen Dämpfung","Domänenwandbewegung","Phononen Rückfaltung","Übergitter Dispersion"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:rights","label":"Dc Rights","values":["Keine öffentliche Lizenz: Unter Urheberrechtsschutz"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["In this thesis, I study ultrafast dynamics in perovskite oxides using time resolved broadband spectroscopy. I focus on the observation of coherent phonon propagation by time resolved Brillouin scattering: following the excition of metal transducer films with a femtosecond infrared pump pulse, coherent phonon dynamics in the GHz frequency range are triggered. Their propagation is monitored using a delayed white light probe pulse. The technique is illustrated on various thin films and multilayered samples. I apply the technique to investigate the linear and nonlinear acoustic response in bulk SrTiO_3, which displays a ferroelastic phase transition from a cubic to a tetragonal structural phase at T_a=105 K. In the linear regime, I observe a coupling of the observed acoustic phonon mode to the softening optic modes describing the phase transition. In the nonlinear regime, I find a giant slowing down of the sound velocity in the low temperature phase that is only observable for a strain amplitude exceeding the tetragonality of the material. It is attributed to a coupling of the high frequency phonons to ferroelastic domain walls in the material. I propose a new mechanism for the coupling of strain waves to the domain walls that is only effective for high amplitude strain. A detailed study of the phonon attenuation across a wide temperature range shows that the phonon attenuation at low temperatures is influenced by the domain configuration, which is determined by interface strain. Preliminary measurements on magnetic-ferroelectric multilayers reveal that the excitation fluence needs to be carefully controlled when dynamics at phase transitions are studied.","In dieser Doktorarbeit untersuche ich ultraschnelle Dynamik in perovskitischen Oxiden mittels zeitaufgelöster optischer Spektroskopie. Der Schwerpunkt liegt dabei auf Phononendynamik, die mithilfe von zeitaufgelöster Brillouin-Streuung sichtbar gemacht wird: durch die Anregung einer metallischen Transducer-Schicht mit einem ultrakurzen Anregepuls wird eine kohärente Phononendynamik im GHz Frequenzbereich erzeugt. Die Ausbreitung der Schallpulse wird mit einem Weißlicht-Abfragepuls aufgezeichnet. Diese Methode wird am Beispiel verschiedener Dünnschicht- und Übergitterproben illustriert. Die Methode und das gewonnene Verständnis wende ich an, um lineare und nichtlineare akustische Eigenschaften an einem SrTiO_3-Kristall zu untersuchen. Dieser weist einen ferroelastischen Phasenübergang von kubischer zu tetragonaler Kristallstruktur bei T_a=105 K auf. Im linearen Regime beobachte ich eine Kopplung der untersuchten akustischen Mode an eine weichwerdende optische Mode, welche den Phasenübergang charakterisiert. Im nichtlinearen Regime tritt eine gigantische Verlangsamung der Schallgeschwindigkeit unterhalb von T_a auf, wenn die induzierte Gitterverzerrung die Tetragonalität des Materials übersteigt. Dies kann auf eine Kopplung der hochfrequenten akustischen Mode an ferroelastische Domänenwände bei tiefen Temperaturen zurückgeführt werden. Ich entwickle einen neuen Mechanismus, der die Kopplung der Verzerrungswelle an die Domänenwände beschreibt. Eine detaillierte Untersuchung der Phononendämpfung in SrTiO_3 über einen weiten Temperaturbereich zeigt, dass diese bei tiefen Temperaturen durch die Domänenkonfiguration beeinflusst ist. Die Domänenkonfiguration ist durch Verzerrungen an der Kristall-Transducer Grenzfläche bestimmt. Erste Untersuchungen an magnetisch-ferroelektrischen Übergittern zeigen, dass die Anregungsfluenz vorsichtig eingestellt werden muss, um die Dynamik an Phasenübergängen zu untersuchen."]},{"key":"dc:format.medium","label":"Dc Format Medium","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Spectroscopic perspectives on ultrafast coupling phenomena in perovskite oxides","Spektroskopische Untersuchung ultraschneller Kopplungsphänomene in Perowskit-Oxiden"]}]}],"canonical_facts":{"dc:contributor":["Bargheer, Matias"],"dc:creator":["Maerten, Lena"],"dc:description.abstract":["In this thesis, I study ultrafast dynamics in perovskite oxides using time resolved broadband spectroscopy. I focus on the observation of coherent phonon propagation by time resolved Brillouin scattering: following the excition of metal transducer films with a femtosecond infrared pump pulse, coherent phonon dynamics in the GHz frequency range are triggered. Their propagation is monitored using a delayed white light probe pulse. The technique is illustrated on various thin films and multilayered samples. I apply the technique to investigate the linear and nonlinear acoustic response in bulk SrTiO_3, which displays a ferroelastic phase transition from a cubic to a tetragonal structural phase at T_a=105 K. In the linear regime, I observe a coupling of the observed acoustic phonon mode to the softening optic modes describing the phase transition. In the nonlinear regime, I find a giant slowing down of the sound velocity in the low temperature phase that is only observable for a strain amplitude exceeding the tetragonality of the material. It is attributed to a coupling of the high frequency phonons to ferroelastic domain walls in the material. I propose a new mechanism for the coupling of strain waves to the domain walls that is only effective for high amplitude strain. A detailed study of the phonon attenuation across a wide temperature range shows that the phonon attenuation at low temperatures is influenced by the domain configuration, which is determined by interface strain. Preliminary measurements on magnetic-ferroelectric multilayers reveal that the excitation fluence needs to be carefully controlled when dynamics at phase transitions are studied.","In dieser Doktorarbeit untersuche ich ultraschnelle Dynamik in perovskitischen Oxiden mittels zeitaufgelöster optischer Spektroskopie. Der Schwerpunkt liegt dabei auf Phononendynamik, die mithilfe von zeitaufgelöster Brillouin-Streuung sichtbar gemacht wird: durch die Anregung einer metallischen Transducer-Schicht mit einem ultrakurzen Anregepuls wird eine kohärente Phononendynamik im GHz Frequenzbereich erzeugt. Die Ausbreitung der Schallpulse wird mit einem Weißlicht-Abfragepuls aufgezeichnet. Diese Methode wird am Beispiel verschiedener Dünnschicht- und Übergitterproben illustriert. Die Methode und das gewonnene Verständnis wende ich an, um lineare und nichtlineare akustische Eigenschaften an einem SrTiO_3-Kristall zu untersuchen. Dieser weist einen ferroelastischen Phasenübergang von kubischer zu tetragonaler Kristallstruktur bei T_a=105 K auf. Im linearen Regime beobachte ich eine Kopplung der untersuchten akustischen Mode an eine weichwerdende optische Mode, welche den Phasenübergang charakterisiert. Im nichtlinearen Regime tritt eine gigantische Verlangsamung der Schallgeschwindigkeit unterhalb von T_a auf, wenn die induzierte Gitterverzerrung die Tetragonalität des Materials übersteigt. Dies kann auf eine Kopplung der hochfrequenten akustischen Mode an ferroelastische Domänenwände bei tiefen Temperaturen zurückgeführt werden. Ich entwickle einen neuen Mechanismus, der die Kopplung der Verzerrungswelle an die Domänenwände beschreibt. Eine detaillierte Untersuchung der Phononendämpfung in SrTiO_3 über einen weiten Temperaturbereich zeigt, dass diese bei tiefen Temperaturen durch die Domänenkonfiguration beeinflusst ist. Die Domänenkonfiguration ist durch Verzerrungen an der Kristall-Transducer Grenzfläche bestimmt. Erste Untersuchungen an magnetisch-ferroelektrischen Übergittern zeigen, dass die Anregungsfluenz vorsichtig eingestellt werden muss, um die Dynamik an Phasenübergängen zu untersuchen."],"dc:format.medium":["application/pdf"],"dc:publisher":["Universität Potsdam"],"dc:rights":["Keine öffentliche Lizenz: Unter Urheberrechtsschutz"],"dc:subject":["coherent phonons","phonon dynamics","time resolved","Brillouin scattering","perovskite oxides","optical spectroscopy","hypersound propagation","phonon damping","domain wall motion","phonon backfolding","superlattice dispersion","kohärente Phononen","Phononen Dynamik","zeitaufgelöst","Brillouin Streuung","Perowskit-Oxide","optische Spektroskopie","Hyperschall Propagation","Phononen Dämpfung","Domänenwandbewegung","Phononen Rückfaltung","Übergitter Dispersion"],"dc:title":["Spectroscopic perspectives on ultrafast coupling phenomena in perovskite oxides","Spektroskopische Untersuchung ultraschneller Kopplungsphänomene in Perowskit-Oxiden"],"dc:type":["doctoralThesis"],"thesis:degree_level":["thesis.doctoral"],"thesis:institution_name":["Universität Potsdam"]},"updated_at":"2026-07-24T03:51:50Z"}