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Andrew Mitchell

Lecturer/Assistant Professor

School Of Physics
Science Centre - North
Belfield
Dublin 4

Tel: +353 1 7162520
Email: andrew.mitchell@ucd.ie

Biography

I am a theoretical physicist working broadly in the area of condensed matter -- in particular theoretical nanoelectronics and topological quantum matter. I am interested in the quantum mechanics of strongly correlated electron systems and many-body theory.

I studied at Oxford University, obtaining my DPhil (PhD) in early 2010. Before starting as an Assistant Professor of Theoretical Physics at UCD, I did postdoctoral research in Cologne (Germany), Oxford (UK), and Utrecht (Netherlands). From 2012-2014 I was a Junior Rersearch Fellow (JRF) at Wadham College in Oxford.

Publications

     

Peer Reviewed Journals

Mitchell, AK; Landau, LA; Fritz, L; Sela, E (2016) 'Universality and Scaling in a Charge Two-Channel Kondo Device'. Physical Review Letters, 116 :157202. Available Online [DOI] [Details]
Vojta, M; Mitchell, AK; Zschocke, F (2016) 'Kondo Impurities in the Kitaev Spin Liquid: Numerical Renormalization Group Solution and Gauge-Flux-Driven Screening'. Physical Review Letters, 117 :037202. Available Online [DOI] [Details]
Mitchell, AK; Fritz, L (2016) 'Signatures of Weyl semimetals in quasiparticle interference'. Physical Review B - Condensed Matter and Materials Physics, 93 :035137. Available Online [DOI] [Details]
Stadler, K; Mitchell, AK, von Delft, J; Weichselbaum, A (2016) 'Interleaved numerical renormalization group as an efficient multiband impurity solver'. Physical Review B - Condensed Matter and Materials Physics, 93 :235101. Available Online [DOI] [Details]
Derry, PG; Mitchell, AK; Logan, DE (2015) 'Quasiparticle interference from magnetic impurities'. Physical Review B - Condensed Matter and Materials Physics, 92 :035126. Available Online [DOI] [Details]
Schwabe, A; Hänsel, M; Potthoff, M; Mitchell, AK (2015) 'Screening mechanisms in magnetic nanostructures'. Physical Review B - Condensed Matter and Materials Physics, 92 :155104. Available Online [DOI] [Details]
Mitchell, AK; Bulla, R (2015) 'Validity of the local self-energy approximation: Application to coupled quantum impurities'. Physical Review B - Condensed Matter and Materials Physics, 92 :155101. Available Online [DOI] [Details]
Mitchell, AK; Fritz, L (2015) 'Kondo effect in three-dimensional Dirac and Weyl systems'. Physical Review B - Condensed Matter and Materials Physics, 92 :121109(R). Available Online [DOI] [Details]
Mitchell, AK; Derry, PG; Logan, DE (2015) 'Multiple magnetic impurities on surfaces: Scattering and quasiparticle interference'. Physical Review B - Condensed Matter and Materials Physics, 91 :235127. Available Online [DOI] [Details]
Galpin, MR; Mitchell, AK; Temaismithi, J; Logan, DE; Béri, B; Cooper, NR (2014) 'Conductance fingerprint of Majorana fermions in the topological Kondo effect'. Physical Review B - Condensed Matter and Materials Physics, 89 :045143. Available Online [DOI] [Details]
Mitchell, AK; Galpin, MR; Wilson-Fletcher, S; Logan, DE; Bulla, R (2014) 'Generalized Wilson chain for solving multichannel quantum impurity problems'. Physical Review B - Condensed Matter and Materials Physics, 89 :121105(R). Available Online [DOI] [Details]
Mitchell, AK; Schuricht, D; Vojta, M; Fritz, L (2013) 'Kondo effect on the surface of three-dimensional topological insulators: Signatures in scanning tunneling spectroscopy'. Physical Review B - Condensed Matter and Materials Physics, 87 :075430. Available Online [DOI] [Details]
Mitchell, AK; Vojta, M; Bulla, R; Fritz, L (2013) 'Quantum phase transitions and thermodynamics of the power-law Kondo model'. Physical Review B - Condensed Matter and Materials Physics, 88 :195119. Available Online [DOI] [Details]
Mitchell, AK; Fritz, L (2013) 'Kondo effect with diverging hybridization: Possible realization in graphene with vacancies'. Physical Review B - Condensed Matter and Materials Physics, 88 :075104. Available Online [DOI] [Details]
Mitchell, AK; Jarrold, TF; Galpin, MR; Logan, DE (2013) 'Local Moment Formation and Kondo Screening in Impurity Trimers'. Journal of Physical Chemistry B, 117 :12777. Available Online [DOI] [Details]
Mitchell, AK; Sela, E; Logan, DE (2012) 'Two-Channel Kondo Physics in Two-Impurity Kondo Models'. Physical Review Letters, 108 :086405. Available Online [DOI] [Details]
Sela, E; Mitchell, AK (2012) 'Local magnetization in the boundary Ising chain at finite temperature'. Journal of Statistical Mechanics: Theory and Experiment, 2012 :P04006. Available Online [Details]
Mitchell, AK; Sela, E (2012) 'Universal low-temperature crossover in two-channel Kondo models'. Physical Review B - Condensed Matter and Materials Physics, 85 :235127. Available Online [DOI] [Details]
Sela, E; Mitchell, AK; Fritz, L (2011) 'Exact Crossover Green Function in the Two-Channel and Two-Impurity Kondo Models'. Physical Review Letters, 106 :147202. Available Online [DOI] [Details]
Mitchell, AK; Becker, M; Bulla, R (2011) 'Real-space renormalization group flow in quantum impurity systems: Local moment formation and the Kondo screening cloud'. Physical Review B - Condensed Matter and Materials Physics, 84 :115120. Available Online [DOI] [Details]
Mitchell, AK; Logan, DE; Krishnamurthy, HR (2011) 'Two-channel Kondo physics in odd impurity chains'. Physical Review B - Condensed Matter and Materials Physics, 84 :035119. Available Online [DOI] [Details]
Mitchell, AK; Logan, DE (2010) 'Two-channel Kondo phases and frustration-induced transitions in triple quantum dots'. Physical Review B - Condensed Matter and Materials Physics, 81 :075126. Available Online [DOI] [Details]
Mitchell, AK; Jarrold, TF; Logan, DE (2009) 'Quantum phase transition in quantum dot trimers'. Physical Review B - Condensed Matter and Materials Physics, 79 :085124. Available Online [DOI] [Details]
Mitchell, AK; Galpin, MR; Logan, DE (2006) 'Gate voltage effects in capacitively coupled quantum dots'. EPL (Europhysics Letters), 76 :95. Available Online [Details]
                                                                                                                                           

Research

Research Interests

Theoretical nanoelectronics:
When nanoscale components are incorporated into electronic circuits, the laws of quantum mechanics govern their basic properties. Striking phenomena such as entanglement and quantum interference can appear, and have no classical analogue. The next generation of miniaturized electronics will overcome the limitations of traditional design paradigms by exploiting the novel functionality of the nano. 

I am interested in developing and applying state-of-the-art theoretical and computational techniques, working closely with experimental collaborators to study and direct development of new nanoelectronic devices. The group is currently working on two key areas of emerging potential. First, we are exploring the rich physics of nanostructures such as semiconductor quantum dots, where strong electron interactions lead to new emergent physics appearing in electron transport measurements. Such devices also represent a paradigm for designer nanophysics, providing a route engineer previously elusive states through quantum simulation of abstract models. 
 
We are also interested in molecular electronics -- especially single molecule junctions. Here, new possibilities arise from the complex interplay between quantum interference due to competing electron transport pathways, and the Kondo effect due to entanglement from strong electronic interactions. Our aim is to address the challenge of how to harness the robust and reproducible chemical complexity provided by nature in single molecule devices. 


Topological Quantum Matter: 
The last decade has seen enormous activity in the research of electronic topological states of matter, sparked by the discovery of topological insulators (TIs), protected by time-reversal symmetry. The nontrivial bulk band topology of 3D strong TIs causes the crossing of surface states at time-reversal invariant points in the surface Brillouin zone, and gives rise to a 2D surface metal. In the vicinity of such crossing points, the effective surface theory takes the form of a Dirac equation of massless fermions, with spin-momentum locking.

Many of the intriguing properties of such systems are however elusive to direct local measurement since, by their very nature, topological features are not local in real-space. However, topological systems can be characterized by their nontrivial response to defects or spin qubits. We are interested in studying such defects in topological materials such as graphene, topological insulators, Dirac and Weyl semimetals, and spin liquids. In particular we develop the theory of experimentally-relevant measurable quantities such as those probed by scanning tunneling spectroscopy (STM) and related quasiparticle interference (QPI), especially in disordered and/or interacting systems.