Dernière mise à jour : 24-11-2017

5 sujets INAC/PHELIQS

• Solid state physics, surfaces and interfaces

• Theoretical Physics

 

Advanced AlGaN-based 1D nanostructure growth for UV emission

SL-DRF-18-0392

Research field : Solid state physics, surfaces and interfaces
Location :

Photonique, Electronique et Ingénierie Quantiques (PHELIQS)

Laboratoire de Nano Physique des Semi-Conducteurs (NPSC)

Grenoble

Contact :

Christophe DURAND

Joël EYMERY

Starting date : 01-10-2018

Contact :

Christophe DURAND

UGA - DRF/INAC/PHELIQS/NPSC

04 38 78 19 77

Thesis supervisor :

Joël EYMERY

CEA - DRF/INAC/MEM/NRS

04 38 78 30 15

The growth of GaN nanowires surrounded by GaN/InGaN quantum wells grown by MOVPE (Metal-Organic Vapor Phase Epitaxy) has been studied extensively in the laboratory and is now well mastered [1]. This is an important step forward as it makes possible the manufacturing and industrial production of nanowire-based LEDs for the emission of visible light (blue, green and white).

In the same way, we wish to develop new 1D nanostructures for the emission of UV light. Pioneering and promising results have been obtained in the laboratory using GaN/InAlN quantum wells grown around the GaN wires exhibiting emission at 330 nm up to room temperature [2]. By applied a in situ annealing, we have demonstrated the possibility of etching the GaN wires core, while preserving the optical properties of the quantum wells. Thus, we made for the first time quantum well-based tubes with excellent optical properties [3].

The aim of the thesis is to develop new quantum wells, such as GaN/AlGaN or AlGaN/AlN grown on 1D nanostructures (wires, tubes, bands, etc.), in order to be able to reach far UV emission wavelengths (<280 nm) with the possibility destroying bacteria. This is a major challenge for the development of UV LEDs considering new applications such as water treatment or sterilization. The purpose of this study is to better understand the potentiality of 1D nanostructures to emit far UV. This type of quantum well grown on 1D nanostructures also makes possible the realization of IR subband detectors in the THz domain.

The development of several stages will be necessary to carry out this thesis project: (i) the realization of 1D nanostructures in Al(Ga)N by combining growth and selective etching, (ii) epitaxy of AlGaN-based quantum wells grown on these nanostructures, (iii) advanced structural and optical characterization, and (iv) the design of new devices and their favrication. The thesis will be based on a collaborator network (C2N, EPFL, Univ. Tyndall ...) in order to progress effectively.

The work is essentially experimental to explore fundamental phenomena at the nanometer scale while participating in a active research topic on the development of new LED devices for UV emission.



[1] R. Koester et al., Nano Lett. 11, 4839 (2011).

[2] C. Durand et al., ACS Photonics 1, 38 (2014).

[3] C. Durand et al., Nano Lett. 17, 3347 (2017).



Theoretical study of advanced magnetocaloric materials

SL-DRF-18-0177

Research field : Solid state physics, surfaces and interfaces
Location :

Photonique, Electronique et Ingénierie Quantiques (PHELIQS)

Groupe Théorie (GT)

Grenoble

Contact :

MIKE ZHITOMIRSKY

Starting date : 01-10-2018

Contact :

MIKE ZHITOMIRSKY

CEA - DRF/INAC/PHELIQS/GT

04.38.78.43.30

Thesis supervisor :

MIKE ZHITOMIRSKY

CEA - DRF/INAC/PHELIQS/GT

04.38.78.43.30

Laboratory link : http://inac.cea.fr/Phocea/Vie_des_labos/Ast/ast_groupe.php?id_groupe=1157

An external magnetic field affects the entropy of a magnetic system and provokes temperature variations which can be used for magnetic refrigeration. Such an alternative cooling technology is increasingly important nowadays for space telescopes, particle physics experiments and quantum computing. The existing adiabatic demagnetization refrigerators utilize paramagnetic salts, which have limited capacity for temperatures above 1 K. Recently, two new families of magnetocaloric materials suitable for applications in the 1-4 K temperature range have been proposed: geometrically frustrated spin systems and dipolar magnets. We plan to study the magnetocaloric properties of such materials using large scale Monte Carlo simulations of realistic spin models appropriate for the known, Gd3Ga5O12 and GdLiF4, as well as for the prospective, Yb2Ti2O7 and Yb3Ga5O12, magnetocaloric materials. The theoretical study will benefit from a collaboration with the on-going experimental work at INAC.

SL-DRF-18-0072

Research field : Solid state physics, surfaces and interfaces
Location :

Photonique, Electronique et Ingénierie Quantiques (PHELIQS)

Laboratoire Silicium Nanoélectronique Photonique et Structures (SINAPS)

Grenoble

Contact :

Emmanuel PICARD

David PEYRADE

Starting date : 01-09-2018

Contact :

Emmanuel PICARD

CEA - DRF/INAC/PHELIQS/SINAPS

04 38 78 90 97

Thesis supervisor :

David PEYRADE

CNRS - LTM

04 38 78 24 53

Interaction effects on topological properties of multiterminal Josephson junctions

SL-DRF-18-0289

Research field : Theoretical Physics
Location :

Photonique, Electronique et Ingénierie Quantiques (PHELIQS)

Groupe Théorie (GT)

Grenoble

Contact :

Julia MEYER

Manuel HOUZET

Starting date : 01-10-2018

Contact :

Julia MEYER

Université Grenoble Alpes - DRF/INAC/PHELIQS/GT

04.38.78.31.46

Thesis supervisor :

Manuel HOUZET

CEA - DRF/INAC/PHELIQS/GT

04.38.78.90.44

Personal web page : http://inac.cea.fr/Pisp/manuel.houzet/

Laboratory link : http://inac.cea.fr/en/Phocea/Vie_des_labos/Ast/ast_groupe.php?id_groupe=501

There is currently an active search for new phases of matter that admit topologically protected edge states. A promising route to realize them consists in combining conventional materials into appropriate heterostructures. Multiterminal Josephson junctions between conventional superconductors may be considered as topological materials themselves. As an example, 4-terminal junctions can accommodate topologically protected zero-energy bound states, which form so-called Weyl singularities. Their existence may be revealed through a quantized transconductance, like in the quantum Hall effect, but without magnetic field. The aim of the project will be to explore further this recent idea by investigating theoretically the robustness of this prediction in the presence of local Coulomb repulsion within the junction. In particular, the fate of Weyl singularities will be analyzed within an actual quantum-dot model for the junction.

Quantum transport in voltage-biased topological Josephson junctions

SL-DRF-18-0281

Research field : Theoretical Physics
Location :

Photonique, Electronique et Ingénierie Quantiques (PHELIQS)

Groupe Théorie (GT)

Grenoble

Contact :

Manuel HOUZET

Julia MEYER

Starting date : 01-10-2018

Contact :

Manuel HOUZET

CEA - DRF/INAC/PHELIQS/GT

04.38.78.90.44

Thesis supervisor :

Julia MEYER

Université Grenoble Alpes - DRF/INAC/PHELIQS/GT

04.38.78.31.46

Personal web page : http://inac.cea.fr/Pisp/julia.meyer/

Laboratory link : http://inac.cea.fr/en/Phocea/Vie_des_labos/Ast/ast_groupe.php?id_groupe=501

Topological phases of matter have attracted much interest in recent years. Topological superconductors are of particular interest because they may host Majorana bound states [1]. Josephson junctions have been proposed as probes of topological superconductivity, and possible signatures of such Majorana bound states in topological Josephson junctions have indeed been observed [2,3,4]. However, important aspects related to the effect of the environment on the properties of the junction are still not fully understood. The aim of the thesis is to make progress in the understanding of quantum transport in voltage-biased topological Josephson junctions in the presence of an electromagnetic environment.

 

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