Anastasia Varlet - ESR7

Anastasia will study spin properties of graphene quantum dots in electron transport experiments in parallel and perpendicular magnetic fields.

email address – varleta@phys.ethz.ch

Host organisation (principal node)
ETH Zurich

Secondary nodes
Delft, Munich

ROLE WITHIN S3NANO

Electronic transport in gate-defined graphene nanostructures.

This project will focus on the realization of gate-defined graphene nanostructures.

One of the criteria for quantum information processing is to have long coherence time of the considered qubit system.  Graphene is therefore expected to be a promising candidate for the realization of spin qubit: being a carbon-based material, its spin coherence time is expected to be long (because of weak spin-orbit coupling and hyperfine interaction) [1].

The realization of graphene spin qubits requires high quality quantum dots.  However getting high quality graphene is challenging. It exhibits a non-negligible disorder, which is mainly due to the environment (substrate and adsorbates). As suspended nanostructures are mechanically unstable, an atomically flat and charge-trap-free substrate such as hexagonal boron nitride [2] is needed to fabricate clean graphene devices by exfoliation.

Another way to improve graphene quality is to find a way to isolate the island without any etching. Bilayer graphene is a solution: by applying an electric field perpendicularly to the bilayer sheet, a band gap can be open [3,4]. This way, nanostructures can be in principle defined via gating, just as it is done with GaAs/AlGaAs quantum dots.

Such gate-defined quantum dots have already been achieved with suspended bilayer graphene [5], and also recently with encapsulated bilayer graphene (bilayer sandwiched between two BN flakes) [6]. But the access to the "clean" excitation spectrum of these charged islands as well as reaching the few electron regime remain challenging.

[1] B. Trauzettel, D.V. Bulaev, D. Loss and G. Burkard, Spin qubits in graphene quantum dots, Nature Physics 3, 192 - 196 (2007)
[2] C. R. Dean, A. F. Young et al., Boron nitride substrates for high-quality graphene electronics ,  Nature Nanotechnology  5, 722–726 (2010)
[3] E. McCann, Asymmetry gap in the electronic band structure of bilayer graphen", Phys. Rev. B 74, 161403(R) (2006)
[4] S. Dröscher, C. Barraud, K. Watanabe, T. Taniguchi, T. Ihn, K. Ensslin, Electron flow in split-gated bilayer graphene, arXiv:1207.4942 (2012)
[5] M. T. Allen, J. Martin, A. Yacoby, Gate-defined quantum confinement in suspended bilayer graphene, Nature Communications 3, 934 (2012).
[6] A. M. Goossens, S. C. M. Driessen, T. A. Baart, K. Watanabe, T. Taniguchi, L. M. K. Vandersypen, Gate-Defined Confinement in Bilayer Graphene-Hexagonal Boron Nitride Hybrid Devices, Nano Lett., Article ASAP

PERSONAL PROFILE

EMPLOYMENT AND TRAINING

Since October 2011
ETH Zürich - Nanophysics Group (Prof. Dr. K. Ensslin - www.nanophys.ethz.ch) - Graphene Team:
Gate-defined nanostructures on BN/Bilayer Graphene/BN heterostructures.

2011 - (5 months)
CNRS – Néel Institute - Grenoble – Nanospintronics and molecular transport group (Dr. W. Wernsdorfer):
Transport in single-molecule magnet-based transistors.
Supervisor: Dr. Franck Balestro

2010 - (10 weeks)
Max Planck Institute for Solid State Research – Von Klitzing Department - MBE Group (Prof. Dr. W. Dietsche) Stuttgart, Germany: work on the role of parallel conduction in GaAs/AlGaAs heterostructures.
Supervisor: Dr. Stefan Schmult

2009 - (1 month)
The sales administration of the company JKR Consulting (telecommunications company): customers and stocks management and commercial experience (phone and physical prospecting).

 

EDUCATION AND QUALIFICATIONS

2010-2011
- 3rd grade in the engineering school called PHELMA (Physics, Electronics, Materials - phelma.grenoble-inp.fr/ ) - Grenoble, France. Specialized in Physics and Nanosciences.
- Double Master Diploma in parallel: Research Master N2 (Nanosciences, Nanotechnologies, speciality « Nanophysics-Nanostructures »).

2009
2nd year in PHELMA – section Physics and Nanosciences.
Research Project: studying and modelling of new reeds for musical instruments.

2008
1st year in PHELMA – section Physics, Electronics and Telecom.
Project: studying and modelling of a solar tower.

2006 – 2008
Preparatory Classes (specialized in Mathematics and Physics). Lycée Thiers - Marseille,
France.

2006
Baccalauréat, scientific section = A-level passed with honors (score > 80%).

 

SPECIFIC SKILLS

RESEARCH INTERESTS - Quantum Transport, Magnetism, Quantum information, Spin physics.

PROGRAMMING LANGUAGES - Maple, C programming, experience in JavaScript and Python languages.

SPECIAL SOFTWARES - MatLab, LabView.

FABRICATION TECHNIQUES - E-Beam lithography, photolithography, RIE, electron beam physical vapor deposition, Atomic Layer Deposition, Scanning Electron Microscopy, Atomic Force Microscopy, electromigration.

EXPERIMENTAL TECHNIQUES - Low temperature measurements (4K to 10mK), under magnetic field (up to 10T).

LANGUAGES

FRENCH - Mother tongue.
ENGLISH - Since 2001: written, spoken and read fluently. TOEFL graduated.
GERMAN - Since 1999: advanced level (2 stays in German families + 10 weeks internship in summer 2010 + PhD work in German-speaking Switzerland