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Ultrafast Electron Dynamics in Corre...

Saha, Tanusree,

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Ultrafast Electron Dynamics in Correlated Systems Probed by Time-Resolved Photoemission Spectroscopy /

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Ultrafast Electron Dynamics in Correlated Systems Probed by Time-Resolved Photoemission Spectroscopy // Tanusree Saha.
作者:	Saha, Tanusree,
面頁冊數:	1 electronic resource (169 pages)
附註:	Source: Dissertations Abstracts International, Volume: 84-12, Section: B.
Contained By:	Dissertations Abstracts International84-12B.
標題:	Physics. -
電子資源:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30525404
ISBN:	9798379599638

Ultrafast Electron Dynamics in Correlated Systems Probed by Time-Resolved Photoemission Spectroscopy /
Saha, Tanusree,

Ultrafast Electron Dynamics in Correlated Systems Probed by Time-Resolved Photoemission Spectroscopy /Tanusree Saha. - 1 electronic resource (169 pages)

Source: Dissertations Abstracts International, Volume: 84-12, Section: B.

Complex systems in condensed matter are characterized by strong coupling between different degrees of freedom constituting a solid. In materials described by many-body physics, these interactions may lead to the formation of new ground states such as excitonic insulators, Mott insulators, and charge and spin density waves. However, the inherent complexity in such materials poses a challenge to identifying the dominant interactions governing these phases using equilibrium studies. Owing to the distinct timescales associated with the elementary interactions, such complexities can be readily addressed in the non-equilibrium regime. Additionally, these materials might also show the emergence of new, metastable "hidden" phases under non-equilibrium. The thesis investigates the ultrafast timescales of fundamental interactions in candidate systems by employing time-and angle-resolved photoemission spectroscopy in the femtosecond time domain. In the (supposed) excitonic insulator model system Ta2NiSe5, the timescale of band gap closure and the dependence of rise time (of the photoemission signal) on the photoexcitation strength point to a predominantly electronic origin of the band gap at the Fermi level. The charge density wave (CDW) - Mott insulator 1T-TaS2 undergoes photoinduced phase transition to two different phases. The initial one is a transient phase which resembles the systems's high temperature equilibrium phase, followed by a long-lived "hidden" phase with a different CDW amplitude and is primarily driven by the CDW lattice order. For the spin density wave system CaFe2As2 where multiple bands contribute in the formation of Fermi surfaces, selective photoexcitation was used to disentangle the role played by different electron orbitals. By varying the polarization of photoexcitation pulses, it is observed that dxz/dyz orbitals primarily contribute to the magnetic ordering while the dxy orbitals have dominant role in the structural order. The findings of the present study provide deeper perspectives on the underlying interactions in complex ground phases of matter, therefore, initiating further experimental and theoretical studies on such materials.

English

ISBN: 9798379599638Subjects--Topical Terms:

516296
Physics.
Subjects--Index Terms:

Charge density wave

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520 $a Complex systems in condensed matter are characterized by strong coupling between different degrees of freedom constituting a solid. In materials described by many-body physics, these interactions may lead to the formation of new ground states such as excitonic insulators, Mott insulators, and charge and spin density waves. However, the inherent complexity in such materials poses a challenge to identifying the dominant interactions governing these phases using equilibrium studies. Owing to the distinct timescales associated with the elementary interactions, such complexities can be readily addressed in the non-equilibrium regime. Additionally, these materials might also show the emergence of new, metastable "hidden" phases under non-equilibrium. The thesis investigates the ultrafast timescales of fundamental interactions in candidate systems by employing time-and angle-resolved photoemission spectroscopy in the femtosecond time domain. In the (supposed) excitonic insulator model system Ta2NiSe5, the timescale of band gap closure and the dependence of rise time (of the photoemission signal) on the photoexcitation strength point to a predominantly electronic origin of the band gap at the Fermi level. The charge density wave (CDW) - Mott insulator 1T-TaS2 undergoes photoinduced phase transition to two different phases. The initial one is a transient phase which resembles the systems's high temperature equilibrium phase, followed by a long-lived "hidden" phase with a different CDW amplitude and is primarily driven by the CDW lattice order. For the spin density wave system CaFe2As2 where multiple bands contribute in the formation of Fermi surfaces, selective photoexcitation was used to disentangle the role played by different electron orbitals. By varying the polarization of photoexcitation pulses, it is observed that dxz/dyz orbitals primarily contribute to the magnetic ordering while the dxy orbitals have dominant role in the structural order. The findings of the present study provide deeper perspectives on the underlying interactions in complex ground phases of matter, therefore, initiating further experimental and theoretical studies on such materials.
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590 $a School code: 2141
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653 $a Complex systems
653 $a Excitonic insulator
653 $a Metastable phase
653 $a Mott insulator
653 $a Non-equilibrium
690 $a 0605
690 $a 0611
710 2 $a University of Nova Gorica (Slovenia). $b Physics. $e degree granting institution. $3 3823883
720 1 $a De Ninno, Giovanni $e degree supervisor.
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