Quantum Transport and far from equilibrium response in nano-junctions

Industry sponsored studentship at the Centre for Doctoral Training in Cross-Disciplinary Approaches to Non-Equilibrium Systems (CANES) 

October 2017 start

This is a collaborative project between King's College London, the National Physics Laboratory (NPL) and Royal Holloway. The project will also involve close collaboration with IBM research laboratories (USA and Switzerland). The aim is to develop a state-of-the-art theoretical framework to model non-equilibrium quantum transport in nano-junctions. This is key for developing new devices for quantum technology. Indeed, in the recent years computer clock speeds have not significantly increased, creating a challenge to invent a successor to CMOS technology. In this project, we will derive a theory to describe quantum transport in nano-devices, and apply the methodology to a new low-voltage piezoelectric transistor (PET). (https://www.petmem.eu).Project Aims:

This project aims to build agent-based models in which algorithmic agents, such as autonomous vehicles, interact with human agents, such as passengers, in electronic markets        underpinned by distributed ledgers and ``smart'' contracts. The project will draw on theoretical and empirical studies of social norms, institutions, trust and reputation, from both multi-agent systems research and the social sciences.  These models will be used to address the following research questions:

- How can we extract complex patterns of behaviour indicating an emerging norm from the vast quantity of mostly unrelated events that occur in a real world system?

- How can we know where to focus detection resources to have most chance of identifying an important emergent behaviour?

- How can we transform a beneficial emergent social norm into one which has enough stability to be relied on by the participants?

- How can we steer the system towards the emergence of robust institutions without undermining trust between agents?  How can we create positive synergy between trust, reputation and institutional rules?

A key part of the methodology of this project will be analysing the steady-state behaviour of these systems, which often exhibit chaotic dynamics and reversals in the flow of conditional entropy between the different micro-level and macro-level descriptions of the system.  Thus this project will require a student who is well versed in techniques for analysing non-equilibrium systems.

Project Aims

The first goal of this project is to advance the quantum transport methods to describe the many-body effects that determine the conductance through nano-materials. This will require the development of a state-of-the-art computational platform to describe quantum many-body non-equilibrium processes in correlated materials. Although electronic structure calculations are nowadays well controlled and understood, in particular via the density functional theory approach (DFT), quantum transport requires extending mathematical tools, such as the non-equilibrium Keldysh Green’s functions. In this project, the student will combine the non-equilibrium Green’s functions (NEGF) technique and the DFT. Quantum conductance in correlated complex materials involve complex interactions, such as the interactions between driven electrons and emergent electronic states (Kondo physics).  In this project, the student will learn the dynamical mean field theory (DMFT) approach, a sophisticated theory based on a mapping of the physical setup to an Anderson impurity problem. The developments made in this project will also be included in the CASTEP software, one of the most-used codes on UK national high-performance computing (HPC) facilities.The second goal is to apply the newly developed methods to piezoresist nanodevices, and to liaise with the experimental partners to guide the device design.

References

1.       S Karan, DJ et al., Phys. Rev. Lett. 115, 016802 (2015). Probing the voltage drop of a molecular junction by the Kondo effect

2.       S. Motahari, R. Requist, and DJ, Phys. Rev. B 94, 235133 (2016). Distributional Exact Diagonalization

3.       C. Weber, D. Cole, D.O’Regan, M. Payne. PNAS 111, 5790 (2014). Renormalization of myoglobin–ligand binding energetics by quantum many-body effects

4.       C Aron, G Kotliar, C Weber, Phys. Rev. Letters 108, 86401 (2012). Dimensional crossover driven by an electric field

5.       A Amaricci, C Weber, M Capone, G Kotliar, Phys. Rev. B 86, 256402 (2012). Approach to a stationary state in a driven Hubbard model coupled to a thermostatEconomic Theory, 78(1), 130–156.

 

Who can apply: UK Students

This studentship is funded for 4 years. Funding covers:

•             A tax-free stipend of around £16,500 per year.

•             Tuition fees.

•             A generous conference travel and internship fund.

Applications will be considered on a rolling basis so interested candidates should apply as soon as possible. To apply please use the link below:

http://www.kcl.ac.uk/innovation/groups/noneqsys/Canes-Programme/Howtoapply.aspx

 

Enquires can be directed to canes@kcl.ac.uk

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