dc.contributor.advisor | Bulutay, Ceyhun | |
dc.contributor.author | Aas, Shahnaz | |
dc.date.accessioned | 2019-11-26T08:31:50Z | |
dc.date.available | 2019-11-26T08:31:50Z | |
dc.date.copyright | 2019-10 | |
dc.date.issued | 2019-10 | |
dc.date.submitted | 2019-11-25 | |
dc.identifier.uri | http://hdl.handle.net/11693/52731 | |
dc.description | Cataloged from PDF version of article. | en_US |
dc.description | Thesis (Ph.D.): Bilkent University, Department of Physics, İhsan Doğramacı Bilkent University, 2019. | en_US |
dc.description | Includes bibliographical references (leaves 52-66). | en_US |
dc.description.abstract | This doctoral thesis deals with optoelectronic and geometric band properties of
two-dimensional transition metal dichalcogenides (TMDs) under applied strain.
First, we analyze various types of strain for the K valley optical characteristics of
a freestanding monolayer MoS2, MoSe2, WS2 and WSe2 within a two-band k p
method. By this simple bandstructure combined with excitons at a variational
level, we reproduce wide range of available strained-sample photoluminescence
data. According to this model strain affects optoelectronic properties. Shear
strain only causes a rigid wavevector shift of the valley without any alternation
in the bandgap or the effective masses. Also, for
exible substrates under applying
stress the presence of Poisson's effect or the lack of it are investigated individually
for the reported measurements. Furthermore, we show that circular polarization
selectivity decreases/increases by tensile/compressive strain for energies above
the direct transition onset.
TMDs in addition to their different other attractive properties have rendered
the geometric band effects directly accessible. The tailoring and enhancement of
these features by strain is an ongoing endeavor. In the second part of this thesis,
we consider spinless two and three band, and spinful four band bandstructure
techniques appropriate to evaluate circular dichroism, Berry curvature and orbital
magnetic moment of strained TMDs. First, we establish a new k p parameter
set for MoS2, MoSe2, WS2 and WSe2 based on recently released ab initio and
experimental band properties. For most of these TMDs its validity range extend
from K valley edge to several hundreds of millielectron volts for both valence and
conduction band. We introduce strain to an available three band tight-binding
Hamiltonian to extend this over a larger part of the Brillouin zone. Based on
these we report that by applying a 2:5% biaxial tensile strain, both the Berry
curvature and the orbital magnetic moment can be doubled compared to their
unstrained values. These simple bandstructure tools can be suitable for the device
modeling of the geometric band effects in strained monolayer TMDs. | en_US |
dc.description.statementofresponsibility | by Shahnaz Aas | en_US |
dc.format.extent | xiii, 66 leaves : charts ; 30 cm. | en_US |
dc.language.iso | English | en_US |
dc.rights | info:eu-repo/semantics/openAccess | en_US |
dc.subject | k - p Hamiltonian | en_US |
dc.subject | Excitons | en_US |
dc.subject | Transition metal dichalcogenides | en_US |
dc.subject | Strain | en_US |
dc.subject | Photoluminescence | en_US |
dc.subject | Circular dichroism | en_US |
dc.subject | Berry curvature | en_US |
dc.subject | Orbital magnetic momen | en_US |
dc.title | A theoretical study of strained monolayer transition metal dichalcogenides based on simple band structures | en_US |
dc.title.alternative | Tek katmanlı gerinimli geçiş metali kalkojenitleri için basit bant yapısına dayalı kuramsal bir çalışma | en_US |
dc.type | Thesis | en_US |
dc.department | Department of Physics | en_US |
dc.publisher | Bilkent University | en_US |
dc.description.degree | Ph.D. | en_US |
dc.identifier.itemid | B160199 | |