Full metadata record
DC Field | Value | Language |
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dc.contributor.advisor | 이재동 | - |
dc.contributor.author | Youngjae Kim | - |
dc.date.accessioned | 2020-06-22T16:02:14Z | - |
dc.date.available | 2020-06-22T16:02:14Z | - |
dc.date.issued | 2020 | - |
dc.identifier.uri | http://dgist.dcollection.net/common/orgView/200000283324 | en_US |
dc.identifier.uri | http://hdl.handle.net/20.500.11750/11991 | - |
dc.description | Ultrafast subfemtosecond dyanmics, light and matter interactions, time-resolved photoemission spectroscopy | - |
dc.description.abstract | We introduce two aspects of the optical pulses (i.e., an audience watching the dynamics and a leading actor raising the dynamics) and demonstrate the interactions in terms of observations of real time-resolved responses and novel applications to open up the fastest electronics. First, we propose a new calculation tech-nique for the time-resolved photoemission spectroscopy that efficiently capture the real-time spectral weights of electronic structures of time-evolving single-particle Kohn-Sham orbitals in solid systems at the extremely ultrashort temporal space. It is found that the calculation can be used to explorer the non-equilibrium phase transitions of strongly correlated electron systems within the frame of the Tran-Blaha exchange potential so that it gives a new insight into the dynamical aspect of Zaanen-Sawatzky-Allen scheme in the case of excited CuO and NiO. We also introduce an appearance of pseudospin-correlated optical transitions in graphene and this would provide a chance to observe the dynamics of pseudospins in emerging materials. Second, control of electrons or their spins in the subfemtosecond time span could become a new pathway to the fastest elec-tronics or spintronics based on the light-wave-induced dynamics. We shall see the applied strain in wide-gap semiconductors is found to be a useful application to manipulate the light-wave-induced current in terms of change in effective mass as a controlling parameter. Also, we provide a smart heterojunction between 2D ferromagnetic transition metal tri-chalcogenide and non-magnetic semiconductor is shown as a petahertz spin device that generate spin filtered current or injector under the strong optical field. We believe our studies on the real-time dynamics provides an unexplored and undefined aspect induced by the optical pulses and suggests new guidance to the meaningful subfemtosecond physics. | - |
dc.description.statementofresponsibility | open | - |
dc.description.tableofcontents | I. Introduction 1.1 Extreme time scale 1 1.2 Ultrafast dynamics in solids 2 1.2.1 Light as an actor: pumping the dynamics 3 1.2.2 Light as an audience: probing the dynamics 3 II. Theoretical frameworks 2.1 Solving Time-dependent Schrödinger’s equations 5 2.1.1 Time-evolved two-level model 5 2.1.2 Dynamics of solid systems 9 2.2 Exact diagonalization for many-body problems 17 2.2.1 Hubbard model 17 2.2.2 Time-evolution of Hubbard system 23 2.3 Density functional theory 27 2.3.1 Kohn-Sham equation 28 2.3.2 Augmented plane wave 31 2.3.3 Local-density approximation 34 2.3.4 Modified Becke-Johnson potential 36 2.3.5 Time-dependent density functional theory 38 2.3.6 Time-resolved angle-resolved photoemission spectroscopy 42 III. Results and discussion I: correlation-dressed excited states of solids 3.1 Correlation-dressed excited states of solids 48 3.2 Correlation induced band mixing in excited states of NiO and CuO 50 3.3 Quantum-phase-dressed excited states of graphene 60 3.4 Conclusion 70 IV. Results and discussion II: Spins at petahertz time scale 4.1 Petahertz frequency control of spins 72 4.2 Model for petahertz spins 74 4.3 TDDFT results of CrPTe3/Sb(111) 83 4.4 Magnetic exchange in the heterostructure 85 4.5 Spin-orbit coupling effect 86 4.6 Conclusion 88 V. Results and discussion III: Subfemtosecond charge driving 5.1 Subfemtosecond charge driving with correlation-assisted band engineering 90 5.2 Band engineering 93 5.3 Excitonic correlation 99 5.4 Conclusion 106 VI. Summary Summary 108 VII. References References 110 |
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dc.format.extent | 136 | - |
dc.language | eng | - |
dc.publisher | DGIST | - |
dc.source | /home/dspace/dspace53/upload/200000283324.pdf | - |
dc.title | Theoretical studies on subfemtosecond dynamics of excited matters | - |
dc.title.alternative | 들뜬 상태에서의 서브펨토초 동역학에 관한 이론적 연구 | - |
dc.type | Thesis | - |
dc.identifier.doi | 10.22677/Theses.200000283324 | - |
dc.description.alternativeAbstract | 본 연구에서 우리는 광의 두 역할을 활용하여 물질로부터의 전자의 극한속도인 수 펨토초 극초고속 시간분해 반응과 동역학의 새로운 활용 가능성에 대하여 이론적 측면의 제안을 하였다. 첫 번째로, 우리는 고체물질 속 단일 전자 Kohn-Sham 오비탈의 실시간 전자구조를 효율적으로 관찰할 수 있는 시간분해 광전자분광 계산 테크닉을 제안하였다. 이 계산에서 우리는 Tran-Blaha 교환 작용으로 기술되는 강상관물질 CuO와 NiO에서 동역학적 Zaanen-Sawatzky-Aallen 과정을 제안하였다. 또한, 우리는 그래핀에서 가짜스핀-연관 광학적 작용을 관찰하였으며, 이는 신물질에서의 가짜스핀 동역학을 연구할 새로운 기회를 제공할 수 있다. 두 번째로, 우리는 빛의 전기장에 의해 유도되는 전자의 극초고속 동역학의 응용성에 관한 연구를 수행하였다. 넓은 갭 반도체에 압력을 가하여, 에너지띠를 변화하여 전자의 유효질량을 변화시키면, 그 물질에서의 빛에 의한 전류를 효과적으로 제어할 수 있음을 알 수 있었다. 또한 마지막으로, 저차원 강자성물질과 비자성 물질의 이종접합을 고려하여 고강도 레이저펄스에 노출시키면, 빛에 의한 전자의 움직임이 순수 스핀의 움직임으로 변환될 수 있음을 발견하였다. 본 연구가 미지의 영역인 전자계 극한 시간영역에서의 움직임과 그 활용을 이해할 수 있는데 기여를 할 수 있을 것이라 기대한다. | - |
dc.description.degree | Doctor | - |
dc.contributor.department | Emerging Materials Science | - |
dc.contributor.coadvisor | Hyunmin Kim | - |
dc.date.awarded | 2020-02 | - |
dc.publisher.location | Daegu | - |
dc.description.database | dCollection | - |
dc.citation | XT.MD 김64 202002 | - |
dc.date.accepted | 2020-01-20 | - |
dc.contributor.alternativeDepartment | 신물질과학전공 | - |
dc.contributor.affiliatedAuthor | Kim, Youngjae | - |
dc.contributor.affiliatedAuthor | Kim, Hyunmin | - |
dc.contributor.affiliatedAuthor | Lee, JaeDong | - |
dc.contributor.alternativeName | 김현민 | - |
dc.contributor.alternativeName | JaeDong Lee | - |
dc.contributor.alternativeName | 김영재 | - |