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Ananthu Surendran - ​ESR 11,  September 2018 - September 2021

Chalmers University of Technology, Gothenburg, Sweden

Master thesis: "Metallic like states on MoS2 using microwave plasma"

MoS2 is one the most studied 2D material post-graphene. The tunable bandgap, superior electrical and mechanical properties and wide availability makes it a promising material for future technological applications. MoS2 possess an array of structural phases of which some of those are metallic in nature. The most sought after metallic state, 1T phase, is produced either by high energy electron beam irradiation or Li intercalation. In this work, we explore the possibility of large scale controllable generation of metallic phase on MoS2 using Microwave forming gas plasma. Our studies focus structural characterisation using Raman scattering experiments and electrical characterisation down to 4K. We observe that the plasma exposed samples develop additional Raman peaks which are considered to belong to a different phase. The electrical characterisation show that the new phase show metallic like conduction down to 4K. The scalable and tunable nature makes this an attractive technique for various future technological applications. Supervisor:  Madhu Thalakulam, QTran Lab,SoP, IISER-TVM.

Personal Training Committee

Main Supervisor: Thilo Bauch, Chalmers

Co-supervisor: Klaus Ensslin, ETH Zurich

Mentor: Amaia Zurutuza, GRA SEMI

Planned secondments

At AALTO, Finland (November 2019) for training in non-equilibrium transport characterisation of S-TI-S hybrid structures.

At GRA SEMI, Spain (June/July 2021) for training in 2D-materials integration.

At UKON, Germany (March 2021) for training in scanning probe microscopy and study of local electrical transport.

PhD project

Transport properties of a hybrid Topological Insulator-superconductor device

Objectives: Our aim is to emulate topological superconductivity in TIs via the proximity effect in hybrid structures using s-wave (Al and Nb) superconductors. Topological superconductors are predicted to host Majorana fermions and are therefore very promising candidates for topologically protected Quantum Information processing. We will study the topologically protected surface electronic state of the TI via the Josephson Effect. For this purpose, we will use nanowires and flakes of Bi2Te3 and Bi2Se3. In order to have a strong Josephson current signal from the bound state (single mode), we will interface the TI nanowires with large gap superconductors such as Nb. In detail, we will be looking for a transition from a 3D to a 2D topological insulator by thinning down the as-grown flakes and nanowires. Such a transition will be detected by a distinct change in the magnetic field response of the Josephson current. Indeed, in 2D TIs the Josephson current will be only carried by the 1D edge states, which results in SQUID-like magnetic field response opposite to a Fraunhofer-like dependence for a 3D TI junction. Moreover, we will integrate the S-TI-S junction, where the TI is in the 2D limit, in a superconducting resonator (collaboration with Early Stage Researcher 14, RAITH, Germany) and perform spectroscopic characterisation of the Andreev bound states localised at the edges. We will explore in collaboration with Early Stage Researcher 4 (AALTO, Finland) the possibility of using S-TI-S hybrid structures for proximity supercurrent detection in thermometry applications at ultra-low temperatures.

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