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Electron-phonon coupling: Computational methods for electronic transport in nanostructures and in bulk materials

Location : CECAM-Lugano, Lugano, Switzerland
October 14, 2019 – October 16, 2019

Real-life performance of semiconductors and metals, whether it being in one, two, or three dimensions, is often limited by carrier scattering by phonons. The mobility of charge is a key parameter in the semiconductor industry to describe the electrical performance and the movement under applied electric fields. The traditional approach to calculate phonon-limited mobilities is based on the Boltzmann transport equation in combination with the effective mass approximation and empirical deformation potentials. Recently, predictive parameter-free mobility calculations have been carried out at the density functional theory (DFT) level for the electron-phonon coupling (EPC) [1-6].

EPC may also lead to a Bose-Einstein condensation of electrons near the Fermi surface as Cooper pairs, resulting in conventional superconductivity at sufficiently low temperatures. Also here DFT calculations of EPC have explained the origin of superconductivity in a range of materials and provided quantitative estimates for the critical temperature using Migdal-Eliashberg theory [7-8]. A recent example includes first-principles theory that revealed how high-pressure hydrogen sulfide is a strongly anharmonic superconductor [9].

In a different context, the introduction of Inelastic Electron Tunneling Spectroscopy together with STM/AFM scanning probe techniques have opened up the possibility to study adsorbates with unprecedented resolution and to characterize inelastic scattering against vibrations down to the single-molecule limit. Ab-initio approaches based on DFT and nonequilibrium Green’s functions (NEGF) have been developed to describe the EPC in such nanoscale junctions and to explain the inelastic transport characteristics [10-12].

Despite the common origin of EPC in these three distinct phenomena (phonon-limited resistivity, phonon-mediated superconductivity and IETS) the systems have traditionally been considered separately by different researchers and with different ab initio methods. In this workshop we propose to convene researchers interested in such EPC physics with the view to foster exchange between people with different approaches and methods.

Some key questions for the discussions would be:
· Ab-initio modelling of EPC in 3D materials: How to deal with the computational complexities of very large systems, such as explicit systems with explicit dopants, layered heterostructures, or organic molecular compounds?
. What are the advantages and limitations of currently available calculational schemes? How can scalability issues and applications to novel materials be addressed?
. Harmonic theory is often applied, but what are the impacts and signatures of anharmonicity in EPC in the derived phenomena (resistivity, superconductivity and IETS)?
. Prospects for a first-principles theory of driven BCS superconductivity?
· Beyond the Boltzmann approach: What can NEGF offer for mobility calculations? Which systems would be prone to interference effects that are beyond a semiclassical description? How to address the high-bias regime?
. How can existing ab initio IETS theory be developed further to describe interfaces and excitation of delocalized phonons?

 

References

Key references:
[1] O. D. Restrepo, K. Varga, and S. T. Pantelides, Appl. Phys. Lett. 94, 212103 (2009).
[2] K. Kaasbjerg, K. S. Thygesen, K. W. Jacobsen, PRB 85, 115317 (2012).
[3] C.-H. Park, N. Bonini, T. Sohier, G. Samsonidze, B. Kozinsky, M. Calandra, F. Mauri, and N. Marzari, Nano Lett. 14, 1113 (2014).
[4] W. Li, PRB 92, 075405 (2015).
[5] T. Gunst, T. Markussen, K. Stokbro, and M. Brandbyge, PRB 93, 035414 (2016).
[6] F. Giustino, Rev. Mod. Phys. 89, 015003 (2017).
[7] M. Calandra and F. Mauri, PRL 95, 237002 (2005).
[8] G. Profeta, M. Calandra, F. Mauri, Nature Physics 8, 131 (2012).
[9] I. Errea, M. Calandra, J. C. Pickard, J. Nelson, R. J. Needs, Y. Li, H. Liu, Y. Zhang, Y. Ma, and F. Mauri, PRL 114, 157004 (2015).
[10] N. Lorente and M. Persson, PRL 85, 2997 (2000).
[11] T. Frederiksen, M. Paulsson, M. Brandbyge, and A.-P. Jauho, PRB 75, 205413 (2007).
[12] H. Nakamura, K. Yamashita, A. R. Rocha, and S. Sanvito, PRB 78, 235420 (2008).

Belgium

Matthieu Verstraete (invited speaker) (Universite de Liege)

Brazil

Alexandre Reily Rocha (invited speaker) (Universidade Federal do ABC, Brazil)

China

Wu Li (invited speaker) (Institute for Advanced Study, Shenzhen University)

Czech Republic

Pavel Jelinek (invited speaker) (Institute of Physics CAS)

Denmark

Mads Brandbyge (invited speaker) (Technical University of Denmark, Lyngby)
Kristen Kaasbjerg (invited speaker) (CAMD, Technical University of Denmark)
Gemma Solomon (invited speaker) (University of Copenhagen)

France

Matteo Calandra (invited speaker) (Sorbonne Université)
Jelena Sjakste (Laboratoire des Solides Irradies, CNRS, Ecole Polytechnique)

Germany

Claudia Draxl (invited speaker) (Humboldt University Berlin)
Frank Ortmann (invited speaker) (Dresden University of Technology)
Dinesh Yadav (University of Konstanz)
Tim Wehling (invited speaker) (University of Bremen)

Ireland

Stefano Sanvito (UCD, Dublin)
Ivana Savic (invited speaker) (Tyndall Natl. Institute)

Japan

Emi Minamitani (invited speaker) (Graduate School of Engineering, University of Tokyo)
Fabian Pauly (invited speaker) (Okinawa Institute of Science and Technology)

Spain

Ion Errea (invited speaker) (University of the Basque Country)

Sweden

Bo Hellsing (invited speaker) (Gotheburg University)

Switzerland

Thibault Sohier (invited speaker) (EPFL)

United Kingdom

Sven Reichardt (invited speaker) (University of Oxford)
Christopher McCooey (Queen’s University Belfast)
Samuel Poncé (invited speaker) (University of Oxford)

Day 1 – Monday October 14, 2019

08:30 to 08:50   Registration

08:50 to 09:00   Welcome

 09:00 to 09:45   Matteo Calandra (CNR and Sorbonne Université, Paris, France)

Anharmonic melting of wharge density wave in single layer TiSe2

09:45 to 10:30   Matthieu Verstraete (University of Liege, Belgium)

Ab initio exciton and phonon dynamics in Transition Metal Dichalcogenides

10:30 to 11:00   Coffee Break

11:00 to 11:45   Mads Brandbyge (Dept. of Physics – Technical University of Denmark)

Large scale at low cost: Electron transport with electron-phonon coupling

11:45 to 12:30   Pavel Jelinek (Institute of Physics, Prague, Czech Republic)

Electron-phonon interaction in 1D molecular chains

12:30 to 13:15   Alexandre Reily Rocha (IFT- Sao Paulo State University, Brazil)

Structural and vibrational properties of water on the surface of a metal: out-of-equilibrium effects

13: 15 to 14:45  Lunch

14:45 to 15:30   Thibault Sohier (Theory and Simulation of Materials (THEOS), and National Centre for Computational Design and Discovery of Novel Materials (MARVEL), École Polytechnique Fédérale de Lausanne, Switzerland)

Electronic transport workflow and high-throughput search for high-mobility 2D materials

15:30 to 16:15   Kristen Kaasbjerg (CAMD, Technical University of Denmark, Denmark)

First-principles modeling of disordered 2D materials

16:15 to 17:15   Discussion

17:15 to 17:45   Coffee Break

17:45 to 20:45   Poster Session

Day 2 – Tuesday October 15, 2019

08:30 to 09:15   Hellsing Bo (Dept. of Physics, Gothenburg University, Sweden)

Electron-phonon coupling in graphene – Linewidths of σ and π bands

09:15 to 10:00   Asier Eiguren (Condensed Matter Physics Dept. Uni. Basque Country (UPV/EHU), Spain and Donostia International Physics Center (DIPC), San Sebastian, Spain)

Efficient calculation electron-phonon related problems thought Helmholtz Fermi Surface harmonics (HFSH)

10:00 to 10:30   Coffee Break

10:30 to 11:15   Samuel Poncé (University of Oxford, United Kingdom)

Predictive calculations of phonon-limited carrier mobilities in semiconductors

11:15 to 12:00   Tim Wehling (University of Bremen, Germany)

 Ab-initio phonon self-energies and fluctuation diagnostics of phonon anomalies

12:00 to 12:45   Raffaello Bianco (Centro de Física de Materiales (CSIC-UPV/EHU), Spain)

 High-temperature superconducting hydrides: the crucial role of quantum anharmonic effects

12:45 to 14:15   Lunch

14:15 to 15:00   Sven Reichardt (University of Oxford, United Kingdom)

First-principles theory of electronic transport beyond the semi-classical Boltzmann equation

15:00 to 15:45   Ivana Savic (Tyndall National Institute, Cork, Ireland)

Simple and accurate Boltzmann transport approach to electronic transport in semiconductors from first principles

15:45 to 16:45   Discussion

16:45 to 17:15   Coffee Break

17:15 to 18:00   Fabian Pauly (Okinawa Institute of Science and Technology, Japan)

Photocarrier thermalization and inelastic effects in quantum transport through nanocontacts

18:00 to 18:45   Wu Li (Institute for Advanced Study, Shenzhen University, China)

Phonon-limited electronic transport and electron-dominated phonon transport from first principles

20:00 to 22:00   Social Dinner

Day 3 – Wednesday October 16, 2019

08:30 to 09:15   Frank Ortmann (Dresden University of Technology, Germany)

Vibrations and their Impact on Electronic and Transport Properties of Organic Materials

09:15 to 10:00   Gemma Solomon (University of Copenhagen, Denmark)

Quantum interference and inelastic transport in molecular junctions

10:00 to 10:30   Coffee Break

10:30 to 11:15   Emi Minamitani (Institute for Molecular Science, Japan)

Ab-initio simulation of phonon related transport phenomena: inelastic electron tunneling spectroscopy & thermal conductivity

11:15 to 12:00   Stefano Sanvito (School of Physics and CRANN, Trinity College Dublin, Ireland)

How do phonons relax molecular spins?

12:00 to 13:00   Discussion

 

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