# Publications

My publications, in reversed chronological order.

## 2021

- Huber, Sebastiaan P., Bosoni, Emanuele, Bercx, Marnik, Bröder, Jens, Degomme, Augustin, Dikan, Vladimir, Eimre, Kristjan, Flage-Larsen, Espen, Garcia, Alberto, Genovese, Luigi,
*Gresch, Dominik*, Johnston, Conrad, Petretto, Guido, Poncé, Samuel, Rignanese, Gian-Marco, Sewell, Christopher J., Smit, Berend, Tseplyaev, Vasily, Uhrin, Martin, Wortmann, Daniel, Yakutovich, Aliaksandr V., Zadoks, Austin, Zarabadi-Poor, Pezhman, Zhu, Bonan, Marzari, Nicola, and Pizzi, GiovanniThe prediction of material properties through electronic-structure simulations based on density-functional theory has become routinely common, thanks, in part, to the steady increase in the number and robustness of available simulation packages. This plurality of codes and methods aiming to solve similar problems is both a boon and a burden. While providing great opportunities for cross-verification, these packages adopt different methods, algorithms, and paradigms, making it challenging to choose, master, and efficiently use any one for a given task. Leveraging recent advances in managing reproducible scientific workflows, we demonstrate how developing common interfaces for workflows that automatically compute material properties can tackle the challenge mentioned above, greatly simplifying interoperability and cross-verification. We introduce design rules for reproducible and reusable code-agnostic workflow interfaces to compute well-defined material properties, which we implement for eleven different quantum engines and use to compute three different material properties. Each implementation encodes carefully selected simulation parameters and workflow logic, making the implementer’s expertise of the quantum engine directly available to non-experts. Full provenance and reproducibility of the workflows is guaranteed through the use of the AiiDA infrastructure. All workflows are made available as open-source and come pre-installed with the Quantum Mobile virtual machine, making their use straightforward.

## 2020

- Pizzi, Giovanni, Vitale, Valerio, Arita, Ryotaro, Blügel, Stefan, Freimuth, Frank, Géranton, Guillaume, Gibertini, Marco,
*Gresch, Dominik*, Johnson, Charles, Koretsune, Takashi, Ibañez-Azpiroz, Julen, Lee, Hyungjun, Lihm, Jae-Mo, Marchand, Daniel, Marrazzo, Antimo, Mokrousov, Yuriy, Mustafa, Jamal I., Nohara, Yoshiro, Nomura, Yusuke, Paulatto, Lorenzo, Poncé, Samuel, Ponweiser, Thomas, Qiao, Junfeng, Thöle, Florian, Tsirkin, Stepan S., Wierzbowska, Małgorzata, Marzari, Nicola, Vanderbilt, David, Souza, Ivo, Mostofi, Arash A., and Yates, Jonathan R.*Journal of Physics: Condensed Matter*2020Wannier90 is an open-source computer program for calculating maximally-localised Wannier functions (MLWFs) from a set of Bloch states. It is interfaced to many widely used electronic-structure codes thanks to its independence from the basis sets representing these Bloch states. In the past few years the development of Wannier90 has transitioned to a community-driven model; this has resulted in a number of new developments that have been recently released in Wannier90 v3.0. In this article we describe these new functionalities, that include the implementation of new features for wannierisation and disentanglement (symmetry-adapted Wannier functions, selectively-localised Wannier functions, selected columns of the density matrix) and the ability to calculate new properties (shift currents and Berry-curvature dipole, and a new interface to many-body perturbation theory); performance improvements, including parallelisation of the core code; enhancements in functionality (support for spinor-valued Wannier functions, more accurate methods to interpolate quantities in the Brillouin zone); improved usability (improved plotting routines, integration with high-throughput automation frameworks), as well as the implementation of modern software engineering practices (unit testing, continuous integration, and automatic source-code documentation). These new features, capabilities, and code development model aim to further sustain and expand the community uptake and range of applicability, that nowadays spans complex and accurate dielectric, electronic, magnetic, optical, topological and transport properties of materials.

- Huber, Sebastiaan P., Zoupanos, Spyros, Uhrin, Martin, Talirz, Leopold, Kahle, Leonid, Häuselmann, Rico,
*Gresch, Dominik*, Müller, Tiziano, Yakutovich, Aliaksandr V., Andersen, Casper W., Ramirez, Francisco F., Adorf, Carl S., Gargiulo, Fernando, Kumbhar, Snehal, Passaro, Elsa, Johnston, Conrad, Merkys, Andrius, Cepellotti, Andrea, Mounet, Nicolas, Marzari, Nicola, Kozinsky, Boris, and Pizzi, Giovanni*Scientific Data*2020The ever-growing availability of computing power and the sustained development of advanced computational methods have contributed much to recent scientific progress. These developments present new challenges driven by the sheer amount of calculations and data to manage. Next-generation exascale supercomputers will harden these challenges, such that automated and scalable solutions become crucial. In recent years, we have been developing AiiDA (aiida.net), a robust open-source high-throughput infrastructure addressing the challenges arising from the needs of automated workflow management and data provenance recording. Here, we introduce developments and capabilities required to reach sustained performance, with AiiDA supporting throughputs of tens of thousands processes/hour, while automatically preserving and storing the full data provenance in a relational database making it queryable and traversable, thus enabling high-performance data analytics. AiiDA’s workflow language provides advanced automation, error handling features and a flexible plugin model to allow interfacing with external simulation software. The associated plugin registry enables seamless sharing of extensions, empowering a vibrant user community dedicated to making simulations more robust, user-friendly and reproducible.

- Yang, Shuyang, Schröter, Niels B. M., Schuwalow, Sergej, Rajpalk, Mohana, Ohtani, Keita, Krogstrup, Peter, Winkler, Georg W., Gukelberger, Jan,
*Gresch, Dominik*, Aeppli, Gabriel, Lutchyn, Roman M., Strocov, Vladimir N., and Marom, Noa2020The electronic structure of surfaces plays a key role in the properties of quantum devices. However, surfaces are also the most challenging to simulate and engineer. Here, we study the electronic structure of InAs(001), InAs(111), and InSb(110) surfaces using a combination of density functional theory (DFT) and angle-resolved photoemission spectroscopy (ARPES). We were able to perform large-scale first principles simulations and capture effects of different surface reconstructions by using DFT calculations with a machine-learned Hubbard U correction [npj Comput. Mater. 6, 180 (2020)]. To facilitate direct comparison with ARPES results, we implemented a "bulk unfolding" scheme by projecting the calculated band structure of a supercell surface slab model onto the bulk primitive cell. For all three surfaces, we find a good agreement between DFT calculations and ARPES. For InAs(001), the simulations clarify the effect of the surface reconstruction. Different reconstructions are found to produce distinctive surface states. For InAs(111) and InSb(110), the simulations help elucidate the effect of oxidation. Owing to larger charge transfer from As to O than from Sb to O, oxidation of InAs(111) leads to significant band bending and produces an electron pocket, whereas oxidation of InSb(110) does not. Our combined theoretical and experimental results may inform the design of quantum devices based on InAs and InSb semiconductors, e.g., topological qubits utilizing the Majorana zero modes.

## 2018

*Gresch, Dominik*, and Soluyanov, Alexey2018The topological phase of non-interacting electronic bandstructure can be classified by calculating integer invariants. In this chapter, we introduce the Chern invariant that classifies 2D materials in the absence of symmetry. We then show that this invariant can be used as the building block for the classification of topological insulators, semimetals, and symmetry-protected topological phases. We show how this classification is performed in practice by introducing Z2Pack, a tool which allows calculating topological invariants from k⋅pk⋅p{}mathbf {k}}}cdot }mathbf {p} and tight-binding models, as well as first-principles calculations.

*Gresch, Dominik*, Wu, QuanSheng, Winkler, Georg W., Häuselmann, Rico, Troyer, Matthias, and Soluyanov, Alexey A.*Physical Review Materials*2018Wannier tight-binding models are effective models constructed from first-principles calculations. As such, they bridge a gap between the accuracy of first-principles calculations and the computational simplicity of effective models. In this work, we extend the existing methodology of creating Wannier tight-binding models from first-principles calculations by introducing the symmetrization post-processing step, which enables the production of Wannier-like models that respect the symmetries of the considered crystal. Furthermore, we implement automatic workflows, which allow for producing a large number of tight-binding models for large classes of chemically and structurally similar compounds or materials subject to external influence such as strain. As a particular illustration, these workflows are applied to strained III-V semiconductor materials. These results can be used for further study of topological phase transitions in III-V quantum wells.

*Gresch, Dominik*2018Geometric properties of electron states in crystalline solids lead to a topological classification of materials. A remarkable consequence of this topological viewpoint is that it reveals a deep link between the bulk properties of a material and electronic states which form on its surface. This leads to unique transport properties, the most well-known example being the integer quantum Hall effect. In topological semimetals, the bulk features of interest are nodes in the band structure, where occupied and unoccupied states are not separated by an energy gap. This leads to interesting low-energy excitations, some of which are the condensed matter equivalent of fundamental particles. The Weyl Fermion for example is realized in topological semimetals, which is theoretically postulated but eludes experimental verification in high-energy physics. Crystals however do not have a continuous translational symmetry, and thus do not need to fulfill the so-called Lorentz invariance present in high-energy physics. This allows for Fermions to exist in materials which do not have a fundamental counterpart. The main topic of this thesis is the study and identification of topological semimetals. We propose a mechanism for Weyl Fermions to form under the influence of an external magnetic field. This effect could help explain the anisotropic negative magnetoresistance in transition metal dipnictides. We also study several novel topological material candidates, hosting a plethora of Weyl Fermions and topological nodal lines. In addition to studying specific material examples, we also present several tools and algorithms which enhance the process of identifying topological materials. First, we present an algorithm for evaluating the phase diagram of a system with discrete phases. This is useful in identifying topological phases, but also applicable to other fields of computational physics. Furthermore, we develop tools that simplify the creation of k·p and tight-binding models to study crystalline systems. A particular focus lies on the construction of models which preserve the crystal symmetries, since these play a crucial role in determining the topology of a material. And finally, we develop an algorithm that reliably finds and classifies topological nodal features.

## 2017

*Gresch, Dominik*, Autès, Gabriel, Yazyev, Oleg V., Troyer, Matthias, Vanderbilt, David, Bernevig, B. Andrei, and Soluyanov, Alexey A.*Physical Review B*2017The intense theoretical and experimental interest in topological insulators and semimetals has established band structure topology as a fundamental material property. Consequently, identifying band topologies has become an important, but often challenging, problem, with no exhaustive solution at the present time. In this work we compile a series of techniques, some previously known, that allow for a solution to this problem for a large set of the possible band topologies. The method is based on tracking hybrid Wannier charge centers computed for relevant Bloch states, and it works at all levels of materials modeling: continuous k⋅p models, tight-binding models, and ab initio calculations. We apply the method to compute and identify Chern, Z2, and crystalline topological insulators, as well as topological semimetal phases, using real material examples. Moreover, we provide a numerical implementation of this technique (the Z2Pack software package) that is ideally suited for high-throughput screening of materials databases for compounds with nontrivial topologies. We expect that our work will allow researchers to (a) identify topological materials optimal for experimental probes, (b) classify existing compounds, and (c) reveal materials that host novel, not yet described, topological states.

*Gresch, Dominik*, Wu, QuanSheng, Winkler, Georg W., and Soluyanov, Alexey A.*New Journal of Physics*2017The transition metal dipnictides TaAs 2 , TaSb 2 , NbAs 2 and NbSb 2 have recently sparked interest for exhibiting giant magnetoresistance. While the exact nature of the magnetoresistance in these materials is still under active investigation, there are experimental results indicating that it is of the anisotropic negative variety. We study the effect of magnetic fields on the band structure topology of these materials by applying Zeeman splitting. In the absence of a magnetic field, we find that the materials are weak topological insulators, which is in agreement with previous studies. When the magnetic field is applied, we find that type-II Weyl points form. This result is found first from a symmetry argument, and then numerically for a ##IMG## [http://ej.iop.org/images/1367-2630/19/3/035001/njpaa5de7ieqn1.gif] {}bfk}cdot }bfp model of TaAs 2 and a tight-binding model of NbSb 2 . This effect could be of help in the search for an explanation of the anomalous magnetoresistance in these materials.

## 2016

- Wang, Zhijun,
*Gresch, Dominik*, Soluyanov, Alexey A., Xie, Weiwei, Kushwaha, S., Dai, Xi, Troyer, Matthias, Cava, Robert J., and Bernevig, B. Andrei*Physical Review Letters*2016Based on the ab initio calculations, we show that MoTe2, in its low-temperature orthorhombic structure characterized by an x-ray diffraction study at 100 K, realizes 4 type-II Weyl points between the Nth and (N+1)th bands, where N is the total number of valence electrons per unit cell. Other WPs and nodal lines between different other bands also appear close to the Fermi level due to a complex topological band structure. We predict a series of strain-driven topological phase transitions in this compound, opening a wide range of possible experimental realizations of different topological semimetal phases. Crucially, with no strain, the number of observable surface Fermi arcs in this material is 2—the smallest number of arcs consistent with time-reversal symmetry.

- Autès, Gabriel,
*Gresch, Dominik*, Troyer, Matthias, Soluyanov, Alexey A., and Yazyev, Oleg V.*Physical Review Letters*2016The recently discovered type-II Weyl points appear at the boundary between electron and hole pockets. Type-II Weyl semimetals that host such points are predicted to exhibit a new type of chiral anomaly and possess thermodynamic properties very different from their type-I counterparts. In this Letter, we describe the prediction of a type-II Weyl semimetal phase in the transition metal diphosphides MoP2 and WP2. These materials are characterized by relatively simple band structures with four pairs of type-II Weyl points. Neighboring Weyl points have the same chirality, which makes the predicted topological phase robust with respect to small perturbations of the crystalline lattice. In addition, this peculiar arrangement of the Weyl points results in long topological Fermi arcs, thus making them readily accessible in angle-resolved photoemission spectroscopy.

- Soluyanov, Alexey A.,
*Gresch, Dominik*, Troyer, Matthias, Lutchyn, Roman M., Bauer, Bela, and Nayak, Chetan*Physical Review B*2016Semiconductor-superconductor heterostructures represent a promising platform for the detection of Majorana zero modes and subsequently the processing of quantum information using their exotic non-Abelian statistics. Theoretical modeling of such low-dimensional heterostructures is generally based on phenomenological effective models. However, a more microscopic understanding of the band structure and, especially, of the spin-orbit coupling of electrons in these devices is important for optimizing their parameters for applications in quantum computing. In this paper, we approach this problem by first obtaining a highly accurate effective tight-binding model of bulk InSb from ab initio calculations. This model is symmetrized and correctly reproduces both the band structure and the wave function character. It is then used to simulate slabs of InSb in external electric fields. The results of this simulation are used to determine a growth direction for InSb nanowires that optimizes the conditions for the experimental realization of Majorana zero modes.

## 2015

- Soluyanov, Alexey A.,
*Gresch, Dominik*, Wang, Zhijun, Wu, QuanSheng, Troyer, Matthias, Dai, Xi, and Bernevig, B. Andrei*Nature*2015Fermions—elementary particles such as electrons—are classified as Dirac, Majorana or Weyl. Majorana and Weyl fermions had not been observed experimentally until the recent discovery of condensed matter systems such as topological superconductors and semimetals, in which they arise as low-energy excitations. Here we propose the existence of a previously overlooked type of Weyl fermion that emerges at the boundary between electron and hole pockets in a new phase of matter. This particle was missed by Weyl because it breaks the stringent Lorentz symmetry in high-energy physics. Lorentz invariance, however, is not present in condensed matter physics, and by generalizing the Dirac equation, we find the new type of Weyl fermion. In particular, whereas Weyl semimetals—materials hosting Weyl fermions—were previously thought to have standard Weyl points with a point-like Fermi surface (which we refer to as type-I), we discover a type-II Weyl point, which is still a protected crossing, but appears at the contact of electron and hole pockets in type-II Weyl semimetals. We predict that WTe2 is an example of a topological semimetal hosting the new particle as a low-energy excitation around such a type-II Weyl point. The existence of type-II Weyl points in WTe2 means that many of its physical properties are very different to those of standard Weyl semimetals with point-like Fermi surfaces.

*Gresch, Dominik*2015The rise of topological insulators, semimetals and superconductors established the topology of the electronic band structure as a fundamental material property. Topological materials can realize exotic novel quantum states such as an integer quantum Hall state in the absence of an external magnetic field, quasiparticle states needed for topological quantum computing, and many more. The topological nature of these states makes them insensitive to small perturbations, which has profound practical consequences. Consequently, the ability to reliably identify topological states is crucial in understanding and predicting many physical effects. In this work, we propose a general approach for calculating any topological invariant, based on the charge centers of hybrid Wannier functions. The method is illustrated in the context of Chern insulators, Z 2 topological insulators and Weyl semi- metals. Most importantly, we present Z2Pack, an easy-to-use software implementing this technique. It can be used as a post-processing tool for first-principles calculations or as a standalone package for tight-binding or k.p models. The fully automated calculation of topological invariants makes Z2Pack ideally suited for both the search for topological states of matter in existing materials and the design of materials or heterostructures with desirable topology.