from Quantum Physics to Nanotechnology


"Nature isn't classical, dammit, and if you want to make a simulation of nature, you'd better make it quantum mechanical, and by golly it's a wonderful problem, because it doesn't look so easy." (R. Feynman, source here)


 

With aggressive miniaturisation of electronic devices, modern technology is based on nanometer-sized devices and hence termed as "Nanotechnology". At this ultra-small scale, the primary focus is to harness the power of quantum nature of materials for the design and optimisation of next generation devices such as super-fast quantum computers, spintronics, high efficiency photovoltaics and thermoelectric, low energy loss photonic devices, sub-nanometer imaging of biomolecules, nano-particle drug delivery systems, etc.       

Our team develops multi-scale theoretical methods based on tight-binding, DFT, and effective-mass approaches to enable quantitative understanding of new and emergent materials in close collaboration with experimentalists, leading to the design and analysis of nano-scale devices operating in quantum mechanical regime. Based on our state-of-the-art simulation framework, we also predict not-yet-fabricated devices with optimised functionalities. Above all, working and understanding physical phenomena at the nanometer scale is absolutely fascinating in itself, as it unravels the complexity used by nature to build everything around us! 




Broad Areas of Interest:

Nanoelectronics, Condensed-Matter Physics, Quantum Physics, High Performance Computing, Engineering Education

Keywords:

Single Impurity Spin Qubits, Quantum Computing Architectures, Quantum Circuits and Simulations, Bismide, Quantum Dot   

Few key questions which motivate our work are:

  • How to exploit the very long coherence time of SiP spin qubits for designing a scalable and universal quantum computing architecture?

  • Can we engineer the wavelength and polarisation properties of III-V QDs for photonic and photovoltaic devices with optimised functionalities? 

  • Can we design Auger-loss free photonic devices from novel bismide materials such as GaBiAs and GaBiNAs with tailored wave lengths? 

  • Audio/Video available online at nanoHUB.org and Youtube: 

    [Video] World's first pinpointing of qubits for quantum computers @ CQC2T, University of Melbourne, and University of New South Wales, Australia

    [Video] Quantum Dot based Photonic Devices @ Physics Department, Dartmouth College, New Hampshire, USA 

    [Audio] Multi-layer QD Stacks for SOAs @ 3rd International Workshop on Epitaxial Growth and Fundamental Properties of Semiconductor Nanostructures, Austria 

    [Audio] Excited State Spectroscopy of a Bilayer QD Molecule @ Electrical & Computer Engineering Department, University of Iowa, Iowa, USA 

    [Audio] Theory of Bismide Alloys @ 2nd International Workshop on Bismuth containing Semiconductors, Surrey University, UK 

    [Audio] Why QD Simulations Must Contain Multi-Million Atoms?   

    [PDF] PhD Research Summary @ Purdue University, Indiana, USA 

    [PDF] Theory of Self-Assembled Quantum Dots - My Ph.D. Thesis @ Purdue University, Indiana, USA 

    Summary of Research Methods:

    The theory and modeling work is based on the following methods:

  • Strain relaxation of atoms in a quantum heterostructure based on atomistic valence force field (VFF) method.

  • Electronic structure calculations based on sp3d5s* tight-binding theory, k.p model, DFT, or some hybrid of these methods.

  • Inter-band optical transition strengths and optical gain from Fermi's Golden rule.

  • Linear and quadratic piezoelectric potentials by solving the Poisson's equation.

  • Multi-particle excitonic spectra from Heitler-London and full configuration interaction (FCI).

  • STM wave function images by coupling Bardeen's tunnelling theory, Chen's derivate rule, and Slater orbitals with tight-binding theory

  • Further details about these methods are presented here: Modeling Methodologies


    Compute Resources:

    Our work is supported by computational resources provided by the following supercomputers:
    • RCAC Purdue University through NCN/Nanohub
    • Magnus Pawsey through NCMAS scheme
    • Raijin NCI through NCMAS scheme
    • Spartan University of Melbourne 

    (1) Are you an experimentalist and interested in our theory? Please feel free to send an email. 

    (2) Are you a student and want to be a part of our team? Please feel free to send an email. 
        For admission and scholarship information, please visit: http://futurestudents.unimelb.edu.au/admissions/scholarships 


    Selected Articles

    Nanoscale 2017

    Visualisation of central-cell-effects in STM images for high-precision donor physics. 
    Nature Nanotechnology 2016

    World's first pinpointing of atoms for quantum computers. (Article Here)

    Nanoscale 2015


    Electric field breaks the strong coupling of quantum dot molecules. (Article Here)

    JPCM (Invited Article) 2015


    Si:As Donor Wave function - Fixing the central-cell corrections in the tight-binding theory. (Article Here)

    PRB 2011, Invited Feature Article


    An elemental change to laser design. (Article Here)

    Nanotechnology 2011, Editor Highlight


    Supercomputers model real-world quantum dot devices atom-by-atom (Article Here)