Research Groups

RESEARCH UNIT: Theory and Simulation

Laboratory of Electronic Structure of Materials (LEEM)

We advance the state of the art in materials design by performing simulations for systems of technological relevance, and in turn by developing and implementing efficient computational methods.

Our group is at the forefront of the development of methods for materials simulation, and also holds a very strong position in their application to a wide range of problems, with a solid network of collaborations. The simulation expertise of the group extends from semi-empirical methods to first-principles approaches. In particular, we are one of the nodes developing the SIESTA program, and contribute to major international initiatives in scientific software.

We have world-class expertise in low-dimensional conductors, in which the particular topologies of the Fermi surface and its nesting properties are responsible for electronic instabilities. In oxide-based systems, we study novel functionalities while at the same time developing accurate modeling strategies to relate the microscopic and macroscopic views of response. Thermal transport at the nanoscale, including its control through external fields, is another relevant area of research.

Members

  • Prof. Enric Canadell - Research Professor
  • Dr. Alberto García - Research Scientist
  • Dr. Riccardo Rurali - Tenured Scientist
  • Dr. Massimiliano Stengel - ICREA Research Professor
  • Dr. Miquel Royo - Postdoctoral Researcher
  • Dr. Madhura Marathe - Postdoctoral Researcher
  • Dr. Konstanze Hahn - Postdoctoral Researcher
  • Dr. Konstantin Shapovalov - Postdoctoral Researcher
  • Dr. Fernán Saiz - Postdoctoral Researcher
  • Dr. Miquel López-Suárez - Postdoctoral Researcher
  • Dr. Pol Torres - Postdoctoral Researcher
  • Dr. Alexander Edström - Postdoctoral Researcher
  • Dr. Emanuele Bosoni - Postdoctoral Researcher
  • Matteo Springolo - PhD Researcher
  • Asier Zabalo - PhD Researcher
  • Andrea Schiaffino - PhD Researcher
  • Juan Antonio Seijas - PhD Researcher
  • Vladimir Dikan - PhD Researcher

Left: First-order charge-density response to individual atomic displacements in bulk Si. Its second moments are called "dynamical quadrupoles" and are an example of spatial dispersion effect.
Right: Unveiling the mechanism of the charge density wave in the Blue Bronze H0.3MoO3: Structure (left). Fitting of the square of the measured frequency of the Kohn anomaly (bottom right) with the calculated electron-hole Lindhard function (top right).

Achievements

Microscopically, the response of crystals to an applied perturbation (e.g., a strain or an electric field) always propagates over a neighborhood around the point of application. At the macroscopic level, this means that the material properties depend on gradients of the applied field, which is known as spatial dispersion. Notable examples of these generally small effects are flexoelectricity, the electrical voltage generated by a flexural deformation, and natural optical activity, the rotation of transmitted light polarization by some crystals. Our recent work provides a general and efficient quantum-mechanical formalism to address this broad class of problems. We have also established, in collaboration with researchers of University of Cantabria, a fundamental theory of quantum capacitance effects in free-electron-like electrodes, analyzing the impact of confinement and other quantum effects on their performance, and identifying previously overlooked mechanisms of relevance for device miniaturization.

In the area of charge density wave (CDW) materials, we could provide for the first time quantitative evidence of the weak electron-phonon coupling scenario for the Peierls distortion in the Blue Bronze system. We were also able to predict the existence of six different atomic structures within a very narrow energy range for the 3×3 CDW modulations of 2H-NbSe2. Careful analysis of theoretical and experimental STM images allowed us to identify two of these CDW structures coexisting in the surface at low temperature.

Other significant front has been the design of materials with tailor-made thermal conductivity and materials whose thermal conductivity can be dynamically tuned by means of external fields.

Most of these developments are grounded in our expertise in the development of first-principles computational methods. In these area, we can highlight the substantial improvements in the efficiency and applicability of the SIESTA code.

 

Publications

Magnetic Molecular Conductors Based on Bis (ethylenedithio) tetrathiafulvalene (BEDT-TTF) and the Tris (chlorocyananilato) ferrate (III) Complex
Suchithra Ashoka Sahadevan, Alexandre Abhervé, Noemi Monni, Pascale Auban-Senzier, Joan Cano, Francesc Lloret, Miguel Julve, Hengbo Cui, Reizo Kato, Enric Canadell, Maria Laura Mercuri, Narcis Avarvari
Inorganic chemistry 58 (22), 15359-15370, 2019

2D Molecular Superconductor to Insulator Transition in the β′′-(BEDT-TTF)2[(H2O)(NH4)2M(C2O4)3]·18-crown-6 Series (M = Rh, Cr, Ru, Ir)
Alexander L Morritt, Jordan R Lopez, Toby J Blundell, Enric Canadell, Hiroki Akutsu, Yasuhiro Nakazawa, Shusaku Imajo, Lee Martin
Inorganic chemistry 58 (16), 10656-10664, 2019

Evidence for the weak coupling scenario of the Peierls transition in the blue bronze
B Guster, M Pruneda, P Ordejón, E Canadell, JP Pouget
Physical Review Materials 3 (5), 055001, 2019

Charge Delocalization, Oxidation States, and Silver Mobility in the Mixed Silver–Copper Oxide AgCuO2¤
Abel Carreras, Sergio Conejeros, Agustín Camón, Alberto García, Nieves Casañ-Pastor, Pere Alemany, Enric Canadell
Inorganic Chemistry 58 (10), 7026-7035, 2019

Coexistence of Elastic Modulations in the Charge Density Wave State of 2H-NbSe2
Bogdan Guster, Carmen Rubio-Verdú, Roberto Robles, Javier Zaldívar, Paul Dreher, Miguel Pruneda, José Ángel Silva-Guillén, Deung-Jang Choi, José I Pascual, Miguel M Ugeda, Pablo Ordejón, Enric Canadell
Nano Letters 19 (5), 3027-3032, 2019

Electronic structure of the α-(BEDT-TTF)2I3 surface by photoelectron spectroscopy
Émilie Tisserond, Niloufar Nilforoushan, Marco Caputo, Pere Alemany, Enric Canadell, Lama Khalil, Ivana Vobornik, Jun Fujii, Pranab Kumar Das, Cécile Mézière, Patrick Batail, Jean-Paul Pouget, Claude Pasquier, Marino Marsi, Miguel Monteverde
The European Physical Journal B 92 (4), 70, 2019

Fermi surface properties of the bifunctional organic metal  κ−(BETS)2 Mn [N (CN)2]3 near the metal-insulator transition
Vladimir N Zverev, Werner Biberacher, Sebastian Oberbauer, Ilya Sheikin, Pere Alemany, Enric Canadell, Mark V Kartsovnik
Physical Review B 99 (12), 125136, 2019

Polarization dependence of angle-resolved photoemission with submicron spatial resolution reveals emerging one-dimensionality of electrons in  NbSe3
MA Valbuena, Piotr Chudzinski, Stephane Pons, Sergio Conejeros, Pere Alemany, Enric Canadell, Helmuth Berger, Emmanouil Frantzeskakis, Jose Avila, Maria Carmen Asensio, Thierry Giamarchi, Marco Grioni
Physical Review B 99 (7), 075118, 2019

Electronic engineering of a tetrathiafulvalene charge-transfer salt via reduced symmetry induced by combined substituents
Yasuhiro Kiyota, Ie-Rang Jeon, Olivier Jeannin, Maxime Beau, Tadashi Kawamoto, Pere Alemany, Enric Canadell, Takehiko Mori, Marc Fourmigué
Physical Chemistry Chemical Physics 21 (40), 22639-22646, 2019

Chiral EDT-TTF precursors with one stereogenic centre: substituent size modulation of the conducting properties in the (R-EDT-TTF) 2 PF 6 (R= Me or Et) series
N Mroweh, P Auban-Senzier, N Vanthuyne, E Canadell, N Avarvari
Journal of Materials Chemistry C 7 (40), 12664-12673, 2019

Charge Delocalization, Oxidation States, and Silver Mobility in the Mixed Silver–Copper Oxide AgCuO2¤
Abel Carreras, Sergio Conejeros, Agustín Camón, Alberto García, Nieves Casañ-Pastor, Pere Alemany, Enric Canadell
Inorganic Chemistry 1, 2019

Electrostatic potential mapping at ferroelectric domain walls by low-temperature photoemission electron microscopy
Jakob Schaab, Konstantin Shapovalov, Peggy Schoenherr, Johanna Hackl, Muhammad Imtiaz Khan, Mario Hentschel, Zewu Yan, Edith Bourret, Claus M Schneider, Slavomír Nemsák, Massimiliano Stengel, Andrés Cano, Dennis Meier
Applied Physics Letters 115 (12), 122903 2019

Disentangling Highly Asymmetric Magnetoelectric Effects in Engineered Multiferroic Heterostructures
Enric Menéndez, Veronica Sireus, Alberto Quintana, Ignasi Fina, Blai Casals, Rafael Cichelero, Mikko Kataja, Massimiliano Stengel, Gervasi Herranz, Gustau Catalán, Maria Dolors Baró, Santiago Suriñach, Jordi Sort
Physical Review Applied 12 (1), 014041, 2019

Mechanisms to enhance the capacitance beyond the classical limits in capacitors with free-electron-like electrodes
J Junquera, P García-Fernández, M Stengel
Physical Review B 99 (23), 235127, 1, 2019

First-principles theory of spatial dispersion: Dynamical quadrupoles and flexoelectricity
M Royo, M Stengel
Physical Review X 9 (2), 021050, 7, 2019

Observation of uncompensated bound charges at improper ferroelectric domain walls
Peggy Schoenherr, Konstantin Shapovalov, Jakob Schaab, Zewu Yan, Edith D Bourret, Mario Hentschel, Massimiliano Stengel, Manfred Fiebig, Andrés Cano, Dennis Meier
Nano Letters 19 (3), 1659-1664, 7, 2019

Metric wave approach to flexoelectricity within density functional perturbation theory
A Schiaffino, CE Dreyer, D Vanderbilt, M Stengel
Physical Review B 99 (8), 085107, 6, 2019

Indications of Phonon Hydrodynamics in Telescopic Silicon Nanowires
Melis, Claudio; Rurali, Riccardo; Cartoixa, Xavier; Xavier Alvarez, F. 
Physical Review Applied, 11, 054059, 2019

Phonon Engineering in Twinning Superlattice Nanowires
De Luca, Marta;  Fasolato, Claudia;  Verheijen, Marcel A.;  Ren, Yizhen;  Swinkels, Milo Y.;  Kolling, Sebastian;  Bakkers, Erik P. A. M.;  Rurali, Riccardo;  Cartoixa, Xavier;  Zardo, Ilaria
Nano Letters, 19, 7, 4702-4711, 2019

Low-temperature thermal rectification by tailoring isotope distributions
Royo, Miguel; Torres, Pol; Lopez-Suarez, Miguel; Rurali, Riccardo 
Physical Review B, 99,024103, 2019

Preferential Positioning, Stability, and Segregation of Dopants in Hexagonal Si Nanowires
Amato, Michele; Ossicini, Stefano; Canadell, Enric; Rurali, Riccardo 
Nano Letters, 19, 2,866-876, 2019

Strain engineering of ZnO thermal conductivity
Antonio Seijas-Bellido, Juan;  Rurali, Riccardo;  Iniguez, Jorge;  Colombo, Luciano;  Melis, Claudio
Physical Review Materials, 3, 065401, 2019

Theoretical investigation of lattice thermal conductivity and electrophononic effects in SrTiO3
Torres, Pol;  Antonio Seijas-Bellido, Juan;  Escorihuela-Sayalero, Carlos;  Iniguez, Jorge;  Rurali, Riccardo
Physical Review Materials, 3, 044404, 2019

Manipulating phonons at the nanoscale: Impurities and boundaries
Zardo, Ilaria; Rurali, Riccardo 
Current Opinion in Green and Sustainable Chemistry, 17, 1-7, 2019

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