東華大學圖書館 |

Exciton Dynamics, Interaction, and Transport in Monolayers of Transition Metal Dichalcogenides /

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Exciton Dynamics, Interaction, and Transport in Monolayers of Transition Metal Dichalcogenides // Saroj Chand.
作者:	Chand, Saroj,
面頁冊數:	1 electronic resource (149 pages)
附註:	Source: Dissertations Abstracts International, Volume: 85-05, Section: B.
Contained By:	Dissertations Abstracts International85-05B.
標題:	Physics. -
電子資源:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30692586
ISBN:	9798380844710

Exciton Dynamics, Interaction, and Transport in Monolayers of Transition Metal Dichalcogenides /
Chand, Saroj,

Exciton Dynamics, Interaction, and Transport in Monolayers of Transition Metal Dichalcogenides /Saroj Chand. - 1 electronic resource (149 pages)

Source: Dissertations Abstracts International, Volume: 85-05, Section: B.

Monolayers Transition metal dichalcogenides (TMDs) have attracted much attention in recent years due to their promising optical and electronic properties for applications in optoelectronic devices. The rich multivalley band structure and sizable spin-orbit coupling in monolayer TMDs result in several optically bright and dark excitonic states with different spin and valley configurations. In the proposed works, we have developed experimental techniques and theoretical models to study the dynamics, interactions, and transport of both dark and bright excitons.In W-based monolayers of TMDs, the momentum dark exciton cannot typically recombine optically, but they represent the lowest excitonic state of the system and can severely affect the overall optical performances. We performed theoretical and experimental studies that show that compressive strain allows us to visualize intervalley momentum dark exciton in the PL spectrum and that these excitons can find application in strain sensing. We show that in monolayer WS2 the formation of momentum dark exciton is greatly enhanced even with small compressive strain due to intervalley electron-phonon coupling, and their spectral properties strongly correlated with the strain magnitude. Furthermore, we show a similar mechanism for WSe2, however, with tensile due to its qualitatively different band structure than WS2. We exploited this correlation for strain sensing in two-dimensional semiconductors, revealing an optical gauge factor exceeding 104. We then focused on spin dark excitons that possess an out-of-plane optical transition dipole, strong binding energy, and long lifetime. Therefore, spin forbidden excitons are promising candidates for interaction-driven long-range transportation. Moreover, these excitons are characterized by lower energy and exhibit a significantly higher density as supported by our theoretical model. By employing a high-resolution spatially resolved PL setup in an encapsulated monolayer of WS2, we demonstrated that the strong repulsive interaction arising from their high density and longer lifetime enables these dark excitons to diffuse up to several micrometers. Furthermore, we conduct experiments in the energy landscape and show that the repulsive interaction can provide energy to dark excitons for transportation even in an uphill energy landscape. This repulsion-driven long-range transport of dark states provides a new route for excitonic devices that could be used for both classical and quantum information processing.Last, we investigated the optical properties of monolayers of TMDs in different structural phases. Monolayers of TMDs occur in the semiconducting 1H phase, whose optical properties are dominated by excitons, and the metallic 1T phase, however less stable than the 1H phase. We developed a method to engineer stable the 1H/1T mixed phase starting with a pristine 1H phase monolayer WS2 by plasma irradiation process. We can control the size of 1T patches by tuning plasma irradiation time. We observe a novel resonance in mixed-phase WS2 monolayers characterized by a lower excitonic energy compared to the bright exciton and exhibits enhanced absorption, extended lifetime, and circular polarization. We attribute the emergence of these unique excitonic states to the interface that forms between two distinct phases. This interpretation gains additional support from our calculations of the dielectric function carried out on the mixed-phase supercell containing both 1H and 1T phases, revealing a novel optical response at lower energies.

English

ISBN: 9798380844710Subjects--Topical Terms:

516296
Physics.
Subjects--Index Terms:

Dark exciton

Exciton Dynamics, Interaction, and Transport in Monolayers of Transition Metal Dichalcogenides /
LDR:05131nmm a22004453i 4500 001 2400477
005 20250522084135.5
006 m o d
007 cr|nu||||||||
008 251215s2024 miu||||||m |||||||eng d
020 $a 9798380844710
035 $a (MiAaPQD)AAI30692586
035 $a AAI30692586
040 $a MiAaPQD $b eng $c MiAaPQD $e rda
100 1 $a Chand, Saroj, $e author. $0 (orcid)0000-0002-5590-2699 $3 3770488
245 1 0 $a Exciton Dynamics, Interaction, and Transport in Monolayers of Transition Metal Dichalcogenides / $c Saroj Chand.
264 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2024
300 $a 1 electronic resource (149 pages)
336 $a text $b txt $2 rdacontent
337 $a computer $b c $2 rdamedia
338 $a online resource $b cr $2 rdacarrier
500 $a Source: Dissertations Abstracts International, Volume: 85-05, Section: B.
500 $a Advisors: Grosso, Gabriele Committee members: Alu, Andrea; Menon, Vinod M.; Sfeir, Matthew Y.; Srivastava, Ajit; Flick, Johannes.
502 $b Ph.D. $c City University of New York $d 2024.
520 $a Monolayers Transition metal dichalcogenides (TMDs) have attracted much attention in recent years due to their promising optical and electronic properties for applications in optoelectronic devices. The rich multivalley band structure and sizable spin-orbit coupling in monolayer TMDs result in several optically bright and dark excitonic states with different spin and valley configurations. In the proposed works, we have developed experimental techniques and theoretical models to study the dynamics, interactions, and transport of both dark and bright excitons.In W-based monolayers of TMDs, the momentum dark exciton cannot typically recombine optically, but they represent the lowest excitonic state of the system and can severely affect the overall optical performances. We performed theoretical and experimental studies that show that compressive strain allows us to visualize intervalley momentum dark exciton in the PL spectrum and that these excitons can find application in strain sensing. We show that in monolayer WS2 the formation of momentum dark exciton is greatly enhanced even with small compressive strain due to intervalley electron-phonon coupling, and their spectral properties strongly correlated with the strain magnitude. Furthermore, we show a similar mechanism for WSe2, however, with tensile due to its qualitatively different band structure than WS2. We exploited this correlation for strain sensing in two-dimensional semiconductors, revealing an optical gauge factor exceeding 104. We then focused on spin dark excitons that possess an out-of-plane optical transition dipole, strong binding energy, and long lifetime. Therefore, spin forbidden excitons are promising candidates for interaction-driven long-range transportation. Moreover, these excitons are characterized by lower energy and exhibit a significantly higher density as supported by our theoretical model. By employing a high-resolution spatially resolved PL setup in an encapsulated monolayer of WS2, we demonstrated that the strong repulsive interaction arising from their high density and longer lifetime enables these dark excitons to diffuse up to several micrometers. Furthermore, we conduct experiments in the energy landscape and show that the repulsive interaction can provide energy to dark excitons for transportation even in an uphill energy landscape. This repulsion-driven long-range transport of dark states provides a new route for excitonic devices that could be used for both classical and quantum information processing.Last, we investigated the optical properties of monolayers of TMDs in different structural phases. Monolayers of TMDs occur in the semiconducting 1H phase, whose optical properties are dominated by excitons, and the metallic 1T phase, however less stable than the 1H phase. We developed a method to engineer stable the 1H/1T mixed phase starting with a pristine 1H phase monolayer WS2 by plasma irradiation process. We can control the size of 1T patches by tuning plasma irradiation time. We observe a novel resonance in mixed-phase WS2 monolayers characterized by a lower excitonic energy compared to the bright exciton and exhibits enhanced absorption, extended lifetime, and circular polarization. We attribute the emergence of these unique excitonic states to the interface that forms between two distinct phases. This interpretation gains additional support from our calculations of the dielectric function carried out on the mixed-phase supercell containing both 1H and 1T phases, revealing a novel optical response at lower energies.
546 $a English
590 $a School code: 0046
650 4 $a Physics. $3 516296
650 4 $a Condensed matter physics. $3 3173567
650 4 $a Optics. $3 517925
653 $a Dark exciton
653 $a Exciton physics
653 $a Exciton transport
653 $a Exciton-exciton interaction
653 $a Phase engineering
653 $a Transition metal dichalcogenides
690 $a 0605
690 $a 0611
690 $a 0752
710 2 $a City University of New York. $b Physics. $e degree granting institution. $3 3770489
720 1 $a Grosso, Gabriele $e degree supervisor.
773 0 $t Dissertations Abstracts International $g 85-05B.
790 $a 0046
791 $a Ph.D.
792 $a 2024
856 4 0 $u https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30692586