Projekt

Controlling excitons in two-dimensional materials

Udbyder

Vejleder

Sted

København og omegn

Just like graphene, a two-dimensional material is an atomically thin sheet of tightly bound atoms, weakly bound to its surroundings through van der Waals forces. Among other advantages, two-dimensional materials are interesting because of the opportunity they give to make atomically sized optical or electronic components. Recently, it has been realized that the class of two-dimensional materials is not limited to graphene but in fact includes hundreds of other materials with diverse properties ranging from insulating, semi-conducting, conducting and superconducting materials. The prospect of using these atomically thin materials for atomic scale devices has lead to a rapid increase in the interest in these materials from the scientific community and the interest has been further supported by experimental demonstrations of actual devices (such as LEDs) constructed by carefully selected two-dimensional materials.

In this project we will investigate the optical properties of two-dimensional semi-conductors like MoS2 focusing on the lowest excited states known as excitons. An exciton is a two-body bound state formed when an electron in the conduction band and a hole in the valence band interact through the attractive coulomb force. States like these are also observed in three-dimensional semiconductors but their binding energy is typically on the order of a few meVs. In contrast, excitons are much more strongly bound in two-dimensional semi-conductors due to their reduced dimensionality. The tuning of excitonic properties by strain have previously been investigated in three dimensional semi-conductors but the achievable strain, on the order of a few %, does not yield significant differences in their excitonic properties. In contrast, strain on the order of 10% is achievable in 2D materials which make it possible to guide excitons by locally straining the 2D semi-conductor to change to exciton binding energy, a principle known as exciton funneling. This has been achived experimentally already by suspending MoS2 on a nano-pillar.

The goals of this project are:
- To calculate exciton binding energies, effective masses and band-gaps as a function of strain in two-dimensional semiconductors, H-MoS2 and black phosporous, which should show opposite trends. This will be done using the density functional theory (DFT) code GPAW which is being developed at our group.

- Employ these parameters to develop an effective medium 2D Mott-Wannier model, with spatially varying material properties, which can be used to simulate larger systems.

The project is well connected to ongoing research activities both within CAMD and at the Center for Nanostructured Graphene (CNG); you will thus be part of a larger team of researchers working on 2D materials and electronic structure theory. The data produced and results obtained in the course of the project will also be beneficial for the 2D Materials Database developed and maintained at CAMD.     

 


Forudsætninger

Knowledge of quantum mechanics

Søg i opslag
Kontakt

Virksomhed/organisation

DTU Fysik

Navn

Kristian Sommer Thygesen

Stilling

Professor

Mail

thygesen@fysik.dtu.dk

Vejleder-info

Bachelor i Fysik og Nanoteknologi

Vejleder

Kristian Sommer Thygesen

ECTS-point

5 - 30

Type

Afgangsprojekt, Bachelorprojekt, Kandidatspeciale, Specialkursus

Kandidatuddannelsen i Elektroteknologi

Vejleder

Kristian Sommer Thygesen

ECTS-point

5 - 30

Type

Afgangsprojekt, Bachelorprojekt, Kandidatspeciale, Specialkursus

Kandidatuddannelsen i Fotonik

Vejleder

Kristian Sommer Thygesen

ECTS-point

5 - 30

Type

Afgangsprojekt, Bachelorprojekt, Kandidatspeciale, Specialkursus

Kandidatuddannelsen i Fysik og Nanoteknologi

Vejleder

Kristian Sommer Thygesen

ECTS-point

5 - 30

Type

Afgangsprojekt, Bachelorprojekt, Kandidatspeciale, Specialkursus

Kandidatuddannelsen i Bæredygtig Energi

Vejleder

Kristian Sommer Thygesen

ECTS-point

5 - 30

Type

Afgangsprojekt, Bachelorprojekt, Kandidatspeciale, Specialkursus

OM DTU

DTU er et teknisk eliteuniversitet med international rækkevidde og standard. Vores mission er at udvikle og nyttiggøre naturvidenskab og teknisk videnskab til gavn for samfundet. 10.000 studerende uddanner sig her til fremtiden, og 5.700 medarbejdere har hver dag fokus på uddannelse, forskning, myndighedsrådgivning og innovation, som bidrager til øget vækst og velfærd.

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Anker Engelunds Vej 1
Bygning 101A
2800 Kgs. Lyngby


45 25 25 25

dtu@dtu.dk

CVR-nr. 30 06 09 46

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