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Ultrafast Spin Dynamics of Quantum M...

Zhang, Haochen,

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Ultrafast Spin Dynamics of Quantum Materials /

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Ultrafast Spin Dynamics of Quantum Materials // Haochen Zhang.
作者:	Zhang, Haochen,
面頁冊數:	1 electronic resource (93 pages)
附註:	Source: Dissertations Abstracts International, Volume: 86-05, Section: B.
Contained By:	Dissertations Abstracts International86-05B.
標題:	Condensed matter physics. -
電子資源:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=31147725
ISBN:	9798342743471

Ultrafast Spin Dynamics of Quantum Materials /
Zhang, Haochen,

Ultrafast Spin Dynamics of Quantum Materials /Haochen Zhang. - 1 electronic resource (93 pages)

Source: Dissertations Abstracts International, Volume: 86-05, Section: B.

The study of spin dynamics in quantum materials has generated ideas about the fundamental understanding of magnetism and the design of novel solid-state devices. In this thesis, we discuss our ultrafast optical studies of the spin dynamics in the hybrid organic-inorganic metal halide perovskite, a new semiconductor material for spintronic applications, and α-RuCl3, a Kitaev quantum spin liquid candidate.Hybrid organic-inorganic metal halide perovskites are emerging materials in photovoltaics and only recently become a promising class of materials for semiconductor spintronics. In two phase-stabilized perovskite thin films (MA0.3FA0.7PbI3 and MA0.3FA0.7Pb0.5Sn0.5I3), we first present temperature dependence of the bandgap using photoluminescence and absorption spectroscopy. Through first-principles calculations, we show the significant impact of thermally induced lattice distortions on the bandgap widening and the different effects on the bandgap from the static and dynamic distortions. Additionally, fluence-dependent photoluminescence measurements demonstrate both the bandgap renormalization and band filling effects.Next, we report a systematic investigation of coherent spin precession, spin dephasing and spin relaxation of electrons and holes in these two perovskites using time-resolved Faraday rotation spectroscopy. With applied in-plane magnetic fields, we observe robust Larmor spin precession of electrons and holes that persists for hundreds of picoseconds. The spin dephasing and relaxation processes are likely to be sensitive to the defect levels. Temperature-dependent measurements give further insights into the spin relaxation channels. The extracted electron Lande g-factors (3.75 and 4.36) are the biggest among the reported values in inorganic or hybrid perovskites. Both the electron and hole g-factors shift dramatically with temperature, which we propose to originate from thermal lattice vibration effects on the band structure. These results lay the foundation for further design and use of lead- and tin-based perovskites for spintronic applications.α-RuCl3 is a Kitaev material suggested to be a proximate quantum spin liquid in a certain temperature and magnetic field range. Nonequilibrium measurements of transient dynamics have been proposed to detect the fractionalized particles that emerge in the spin liquid and to possibly drive the system into novel photoinduced magnetic states that cannot be accessed by conventional equilibrium probes. Here we study ultrafast spin dynamics of photoinduced excitations in α-RuCl3 using pump-probe transient grating spectroscopy. In the real part of the complex transient reflectance change ∆r/r, we observe evidence of long-range antiferromagnetic correlations near the Neel temperature. Most intriguingly, above the Neel temperature in the Kitaev paramagnetic phase, we reveal a photoexcitation component sensitive to the in-plane magnetic field in the imaginary part of ∆r/r. This component exhibits two distinct lifetimes of about tens of picoseconds. This photoexcitation component may be connected to novel photoexcited states in the Kitaev quantum spin liquid, and its lifetimes likely reflect the dynamics of unconventional spin excitations in the Kitaev model.

English

ISBN: 9798342743471Subjects--Topical Terms:

3173567
Condensed matter physics.
Subjects--Index Terms:

Spin dynamics

Ultrafast Spin Dynamics of Quantum Materials /
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520 $a The study of spin dynamics in quantum materials has generated ideas about the fundamental understanding of magnetism and the design of novel solid-state devices. In this thesis, we discuss our ultrafast optical studies of the spin dynamics in the hybrid organic-inorganic metal halide perovskite, a new semiconductor material for spintronic applications, and α-RuCl3, a Kitaev quantum spin liquid candidate.Hybrid organic-inorganic metal halide perovskites are emerging materials in photovoltaics and only recently become a promising class of materials for semiconductor spintronics. In two phase-stabilized perovskite thin films (MA0.3FA0.7PbI3 and MA0.3FA0.7Pb0.5Sn0.5I3), we first present temperature dependence of the bandgap using photoluminescence and absorption spectroscopy. Through first-principles calculations, we show the significant impact of thermally induced lattice distortions on the bandgap widening and the different effects on the bandgap from the static and dynamic distortions. Additionally, fluence-dependent photoluminescence measurements demonstrate both the bandgap renormalization and band filling effects.Next, we report a systematic investigation of coherent spin precession, spin dephasing and spin relaxation of electrons and holes in these two perovskites using time-resolved Faraday rotation spectroscopy. With applied in-plane magnetic fields, we observe robust Larmor spin precession of electrons and holes that persists for hundreds of picoseconds. The spin dephasing and relaxation processes are likely to be sensitive to the defect levels. Temperature-dependent measurements give further insights into the spin relaxation channels. The extracted electron Lande g-factors (3.75 and 4.36) are the biggest among the reported values in inorganic or hybrid perovskites. Both the electron and hole g-factors shift dramatically with temperature, which we propose to originate from thermal lattice vibration effects on the band structure. These results lay the foundation for further design and use of lead- and tin-based perovskites for spintronic applications.α-RuCl3 is a Kitaev material suggested to be a proximate quantum spin liquid in a certain temperature and magnetic field range. Nonequilibrium measurements of transient dynamics have been proposed to detect the fractionalized particles that emerge in the spin liquid and to possibly drive the system into novel photoinduced magnetic states that cannot be accessed by conventional equilibrium probes. Here we study ultrafast spin dynamics of photoinduced excitations in α-RuCl3 using pump-probe transient grating spectroscopy. In the real part of the complex transient reflectance change ∆r/r, we observe evidence of long-range antiferromagnetic correlations near the Neel temperature. Most intriguingly, above the Neel temperature in the Kitaev paramagnetic phase, we reveal a photoexcitation component sensitive to the in-plane magnetic field in the imaginary part of ∆r/r. This component exhibits two distinct lifetimes of about tens of picoseconds. This photoexcitation component may be connected to novel photoexcited states in the Kitaev quantum spin liquid, and its lifetimes likely reflect the dynamics of unconventional spin excitations in the Kitaev model.
546 $a English
590 $a School code: 0779
650 4 $a Condensed matter physics. $3 3173567
650 4 $a Materials science. $3 543314
650 4 $a Physical chemistry. $3 1981412
650 4 $a Quantum physics. $3 726746
650 4 $a Analytical chemistry. $3 3168300
653 $a Spin dynamics
653 $a Photoluminescence measurements
653 $a Spintronic applications
653 $a Absorption spectroscopy
653 $a Kitaev material
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690 $a 0599
690 $a 0794
690 $a 0486
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710 2 $a University of Toronto (Canada). $b Physics. $e degree granting institution. $3 3817096
720 1 $a Yang, Luyi $e degree supervisor.
773 0 $t Dissertations Abstracts International $g 86-05B.
790 $a 0779
791 $a Ph.D.
792 $a 2024
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