Title: Magnetism and topology in two-dimensional materials
Tutor: Prof. Marco Gibertini
Abstract: Reducing the thickness of layered materials down to the ultimate monolayer limit can disclose manifold unexpected phenomena. Among these, two appear to be particularly fascinating. On one side magnetism that, although becoming more fragile in 2D, can occur in unprecedented phases (like the Berezinskii–Kosterlitz–Thouless phase) and can be easily manipulated through electric fields, doping, etc. On the other side, 2D materials can host topological states of matter like the quantum spin-Hall phase or, in combination with magnetism, the anomalous Hall phase. This project will focus on the prediction of novel magnetic and topological 2D materials from first-principles simulations and their characterization towards spintronics and valleytronics applications, in collaboration with experimental groups.
Collaborations: Theory: Prof. Nicola Marzari (EPFL, Switzerland), Dr Silvia Picozzi (SPIN-CNR, Chieti), Dr Antimo Marrazzo (SISSA). Exp: Prof. Alberto Morpurgo (U. Geneva, Switzerland)
References:
npj 2D Materials and Applications (2022)
Phys. Rev. Research 2, 012063(R) (2020)
Nature Nanotechnology 14, 1116 (2019)
Title: Phonons and electron-phonon interactions in low-dimensional materials
Tutor: Prof. Marco Gibertini
Abstract: In low-dimensional materials, electrostatic effects become subtle as most of the field lines extend outside the material and are thus not screened by electrons. This is particularly relevant when describing long wavelength perturbations that give rise to finite electric fields, such as longitudinal optical phonons. The aim of this project is to formulate a proper description of long-range electrostatic effects on phonons and electron-phonon interactions in low-dimensional materials, possibly including the effect of screening from free carriers in the system. These aspects are crucial to obtain realistic predictions for transport and spectroscopic responses from first-principles simulations, in close collaboration with experiments. Moreover, this description might provide a sound starting point to develop a model to combine the response of different low-dimensional materials to account for remote screening/electron-phonon coupling without the need for direct expensive calculations of heterostructures.
Collaborations: Dr Thibault Sohier (CNRS Montpellier, France), Dr Francesco Macheda (La Sapienza, Italy), Dr Massimiliano Stengel (ICREA, Spain), Prof Samuel Poncé (U. Louvain, Belgium), Prof Nicola Marzari (EPFL, Switzerland).
References:
Phys. Rev. B 107, 155424 (2023)
Phys. Rev. Materials 5, 024004 (2021)
Phys. Rev. Materials 2, 114010 (2018)
Title: Extending the scope of first principles spectroscopy with method and algorithmic development
Tutor: Prof. Marco Govoni
Abstract: The simulation of light activated processes in materials for energy sustainability and quantum information science requires a robust description of neutral excitations in complex heterogeneous systems. In this program we will develop a hierarchical modeling approach that enables us to simulate neutral excitations in materials with increasing complexity. We will carry out the simulation of excitons for large systems using TDDFT and BSE, with GPU and machine learning acceleration. The simulation of neutral excitations in the presence of structural relaxations will be carried-out using the Huang-Rhys theory. Weak and strong electron correlation regimes will be studied using time-dependent density functional theory / many-body perturbation theory, and a quantum embedding theory based on Green’s function theory, respectively. Key science questions that will guide this research include: Which numerically manageable approximations allow us to simulate neutral excitations for large heterogenous systems? What are the key factors that play a crucial role in developing robust quantum embedding methodologies? How can we efficiently simulate structural relaxation in the excited states? The student will have the opportunity to advance the state-of-the-art electronic structure calculations by developing strategies to leverage emerging trends in the high-performance computing landscape, which include exascale and quantum computing.
Collaborations: Theory: G. Galli (UChicago, USA), F. Gygi (UCDavis, USA), J. Whitmer (U Notre Dame, USA). Experiment: J. Heremans (ANL, USA), J. Forneris (UTorino). Computational facilities: CINECA, IBM-Quantum.
References: for further details, please contact mgovoni@unimore.it
Title: Theoretical modeling of Coulomb driven non-radiative recombination mechanisms
Tutor: Prof. Ivan Marri, Prof. Marco Govoni
Abstract: Coulomb-driven non-radiative recombination mechanisms, e.g. the Auger recombination (AR) and its counterpart Carrier multiplication (CM), strongly affect excited state dynamics in low dimensional systems. A theoretical modeling of these mechanisms is fundamental to (i) support pump and probe experimental investigations of photo-excited carriers evolution and (ii) to design novel efficient materials for optoelectronic and photovoltaic applications.
The goal of this project is the development of advanced highly-parallelized tools for the calculation of pure collisional and phonon-assisted AR and CM lifetimes with the inclusion of Many-Body effects. The tools will be applied to modeling AR and CM processes in 2D material and nanocrystals, to investigare effects induced by energy and charge transfer processes in systems of strongly interacting nanostructures and finally to investigate single-fission processes.
Collaborations: Prof. Olivia Pulci and Prof. Maurizia Palummo, Università degli studi di Roma Tor Vergata.
References and links:
[1] https://doi.org/10.1103/PhysRevB.84.075215
[2] https://doi.org/10.1038/nphoton.2012.206
[3] https://doi.org/10.1021/ja5057328
[4] http://dx.doi.org/10.1039/D1NR01747K
For further details please contact: marri@unimore.it
Title: Theoretical study of nonlinear optical processes at soft x-ray wavelengths as a new powerful approach to the study of surfaces and interfaces for specific technological applications.
Tutor: Prof. Elena Degoli (Unimore)
Abstract: This project, through ab-initio calculations, aims to explore and demonstrate the potential of nonlinear optical processes in the soft x-ray wavelength range for the characterization of surfaces and interfaces.
Recently, significant progress has been made at the FERMI free electron laser (FFEL) in Trieste, where high-intensity and coherent soft x-ray pulses have successfully generated soft x-ray SHG from both surfaces and buried interfaces. In collaboration with our partners at FFEL, as well as Sorbonne Universitè and Ecole Polytechnique in Paris, we will combine experimental data and first-principles calculations to showcase the selective probing capabilities of these techniques for surfaces and interfaces.
We aim to provide a new powerful combined theoretical and experimental tool for surface and interface analysis, applicable to various scientific fields from optoelectronics, photovoltaics to all-solid Li ions batteries. By combining the elemental and chemical specificity of x-ray absorption spectroscopy with the precise interfacial specificity of second-order nonlinear spectroscopies and exploiting the predictive and interpretative capabilities of the theoretical simulations, we could obtain comprehensive information on systems whose structural nature is not otherwise accessible.
Collaborations: Prof. Eleonora Luppi (Laboratoire de Chimie Theorique, Sorbonne Universitè, Paris, France), Dr. Emiliano Principi at Fermi Free Electron Laser, Trieste, Dr. Valèrie Veniard Laboratoire des Solides Irradiès, CNRS, CEA/DRF/IRAMIS, Ecole Polytechnique de Paris, Palaiseau, France, European Theoretical Spectroscopy Facility, Palaiseau, France
References & links:
Eur. Phys. J. Spec. Top. (2022). https://doi.org/10.1140/epjs/s11734-022-00677-5
Phys. Rev. Lett. (2018) https://doi.org/10.1103/PhysRevLett.120.023901
Phys. Rev. Lett. (2021) https://doi.org/10.1103/PhysRevLett.127.096801
For further details, please contact elena.degoli@unimore.it
Title: Machine learning aided ab initio spectroscopies for interfaces and interphases in next-generation battery materials
Tutor: Elisa Molinari, co-Tutor: Federico Grasselli, Deborah Prezzi
Abstract: The PhD candidate will develop automated protocols for calculating operando core level and vibrational spectra from first principles, focusing on interfaces and interphases in Li-based chemistries and beyond. Objectives include combining direct calculations of spectra with advanced schemes based on local topologies and bond graphs. Machine-learning surrogate models based on density-related descriptors will be used to obtain a direct prediction of the spectra starting from a single representative configuration. The challenging inverse problem of generating structures from spectra will also be investigated. The project will establish a feedback loop with experimental results for validation and it will enhance in-operando materials characterization through computational insights. Outcomes will include comprehensive atlases of spectroscopic fingerprints and advanced methods for spectral prediction and analysis, significantly advancing material characterization and predictive capabilities in materials science.
Collaborations: Prof Michele Ceriotti (EPFL, Lausanne), dr Sandrine Lyonnard (CEA & ESRF, Grenoble).
Title: Plasmons, excitons, and emerging electronic orders in mono- and bilayer semimetals
Tutor: Elisa Molinari, Massimo Rontani and Daniele Varsano
Abstract: Both excitons and plasmons are collective, neutral excitations of solids that arise as a consequence of the long range of Coulomb forces. Whereas excitons are traditionally investigated in semiconductors and plasmons in metals, new mono- and bi-layer semimetals, such as MoTe2 , WTe2, HfTe2 , provide a novel playground for exotic, hybrid exciton-plasmon excitations.
Importantly, the anomalies in the system’s dielectric response due to these peculiar collective modes might shed light into the onset of fascinating electronic states. These phases include correlated (excitonic) insulators, electronic ferroelectrics, and unconventional superconductors, which are observed in the proposed systems but poorly understood.
This Thesis will investigate exciton-plasmons through accurate many-body perturbation theory from first principles and modelling of correlated phases.
This work is planned within the wider framework of collaborative research with the experimental groups of Transmission Electron Microscopy (FIM and CNR-NANO) and quantum transport (Univ Washington, Seattle), aiming at the quantitative interpretation of relevant spectroscopies such as electron energy loss.
Collaborations: Claudia Cardoso and Andrea Ferretti (Cnr-Nano); Stefano Frabboni, Vincenzo Grillo, Giovanni Bertoni (TEM team, Unimore and Cnr-Nano); David Cobden (Univ Washington, WA, Usa), Hope Bretscher (Univ Columbia, NY, USA).
References:
[1] Sun et al, Nat Phys 18, 87 (2022); Jindat et al, Nature 613, 48 (2023); Gao et al, Nat Phys 20, 597 (2024).
[2] Group website: https://excitonic-insulator.nano.cnr.it/.
Title: Exciton dynamics in 2D materials: development and applications
Tutor: E. Molinari, A. Ferretti, D. Varsano
Abstract: The main aim of this project is the development of a computational methodology, based on Green’s function methods, to describe from first principles the coupled and non-adiabatic dynamics of electrons and ions during the excitation of 2D materials [1,2]. Relevant tasks to be addressed are:
(i) the computational development of a Ehrenfest scheme for nuclear motion, to be coupled with the electronic dynamics treated using time-dependent Hartree + Screened exchange approximation;
(ii) the development and implementation of ad hoc convergence accelerators specialized to Green’s function methods applied to 2D materials [2,3,4,5];
(iii) the application of the developed methodology to selected 2D materials, especially focused at describing pump-probe experiments;
(iv) understanding the possible interaction with Artificial intelligence schemes, including the ability to produce accurate data for training as well as the explicit usage of AI methods to accelerate the computational Green’s function framework.
Collaborations: D. Sangalli (Cnr-Ism), F. Paleari, C. Cardoso, M. Rontani (Cnr-Nano), and the Yambo team @ MaX European Centre of Excellence
References:
[1] M. Zanfrognini, et al, Phys. Rev. Lett. 131, 206902 (2023).
[2] A. Guandalini et al, Nano Lett. 23, 11835 (2023).
[3] D.A. Leon et al, Phys. Rev. B 107, 064006 (2023).
[4] A. Guandalini et al, npj Comput. Mater. 9, 44 (2023).
[5] D Sangalli et al, J. Phys.: Condens. Matter 31 325902 (2019).
Title: Electron-phonon coupling beyond the linear regime
Tutor: Dott. Raffaello Bianco
Abstract: The linear coupling between phonons and electrons serves as the fundamental method for computing the contribution of nucleus-electron interactions to material properties from first principles. However, in certain materials, such as doped manganites, halide perovskites, and quantum paraelectrics, or in systems exhibiting superconductivity and charge-density-wave correlations, there is evidence that nonlinear coupling between electrons and atomic displacements plays a significant role. These findings have sparked interest in exploring new methods to accurately include nonlinear electron-phonon interactions from first principles. Building on a novel approach presented in [1], this project will focus on studying the electrical transport and structural properties of materials where current models based on linear electron-phonon coupling fail to match experimental results. The project will involve methodological developments, numerical implementations, and applications to calculate the properties of these materials.
Collaborations: Prof. Ion Errea (UPV/EHU, Spain), dott. Dino Novko (IoP, Croatia)
References: https://arxiv.org/abs/2303.02621
Title: Efficient inclusion of quantum and anharmonic effects in nuclei dynamics’ calculations
Tutor: Dott. Raffaello Bianco
Abstract: The atomic motion is crucial in many important properties of materials, such as electrical/thermal transport, phase transitions, and vibrational spectra. However, simulating the dynamics of nuclei from first principles becomes exceptionally challenging when quantum/thermal fluctuations are relevant (e.g., at high temperatures or with light atoms) and the potential energy of nuclei is anharmonic. Significant progress has been made in recent decades in implementing new approaches to efficiently include quantum and anharmonic effects in the dynamics of nuclei, specifically with SSCHA [1,2]. This project will focus on further developments of the SSCHA method to improve its capabilities and competitiveness compared to other more computationally demanding techniques. The project will include methodological developments, numerical implementations, and applications to calculate materials’ properties, such as perovskites and high-Tc superconductors.
Collaborations: Prof. Ion Errea (UPV/EHU, Spain)
References:
[1] https://sscha.eu/[2] Journal of Physics: Condensed Matter 33, 363001 (2021)
Title: High-performance Computational Design of Materials and Architectures for Semiconductor Quantum Wires with Enhanced Thermoelectric Performance
Tutor: Alice Ruini (FIM, UniMoRe)
Co-tutor: Pino D’Amico (CnrNano)
Abstract: Thermoelectric materials play a crucial role in energy harvesting and solid-state cooling applications by converting waste heat into electricity and vice versa. However, the efficiency of thermoelectric devices depends on intricate interactions between phonons and electrons: the evaluation of the thermoelectric figure-of-merit is a challenging task. We here aim to contribute to the advancement of atomistic simulations in thermoelectric materials research, by efficiently combining density functional theory [1] and Boltzmann transport equation [2], and possibly implementating a greatly accelerated approach to evaluate anharmonic constants via machine-learning interatomic potentials trained over short ab-initio MD trajectories. Final goal is the computational design of novel semiconductor quantum wires with superior thermoelectric performance. According to the interests of the candidate, the proposed research could include a strict synergy with experimental activities.
Main collaboration: Prof. F. Rossella (FIM, UniMoRe)
References:
[1] www.quantum-espresso.com
[2] A. Cepellotti et al “Phoebe: a high-performance framework for solving phonon and electron Boltzmann transport equations”, J. Phys. Mater. 5 035003 (2022)
For further details contact alice.ruini@unimore.it
Title: Novel numerical approaches for the atomistic description of disordered systems
Tutor: Dr. Arrigo Calzolari (CNR-NANO) and Prof. Alice Ruini (FIM, UniMoRe).
Abstract: By using multiscale/multiphysics theoretical approaches, this thesis aims at investigating disordered metallic systems (e.g. amorphous, glasses), as advanced materials for photonics and electronics. The main goal is the development of novel computational approaches that – combining e.g. themodynamics, molecular dynamics, montecarlo and machine learning – provide an atomistic representation of disordered systems with minimal sizes, which may be further affordable for quantum mechanical investigations. The activity will benefit by well‐established collaborations with (inter)national theoretical groups.
Collaborations: Francesco Tavanti (CNR-NANO), Stefano Curtarolo (Duke Univ. NC USA).
References & links: For further details and references see http://amuse.nano.cnr.it or contact arrigo.calzolari@nano.cnr.it
Title: Prediction of novel Magnetic Transparent Conductors for spintronic applications
Tutor: Prof. Alice Ruini (FIM, UniMoRe).
Co-Tutors: Dr. Pino D’Amico (CNR NANO), Dr. Arrigo Calzolari (CNR NANO)
Abstract: Transparent Conductors (TCs) exhibit optical transparency and electron conductivity, and are essential for many opto-electronic and photo-voltaic devices. The most common TCs are electron-doped oxides, which have few limitations when transition metals are used as dopants. Non-oxides TCs have the potential of extending the class of materials to the magnetic realm, bypass technological bottlenecks, and bring TCs to the field of spintronics [1]. In this thesis we aim at investigating new functional materials that combine transparency and conductivity with magnetic spin polarization that can be used for spintronic applications, such as spin filters. By employing ab-initio approaches, Boltzmann transport theory, high-throughput and spectral operator representations techniques [2], we aim at the discovery of a new class of potential magnetic TCs.
Collaborations: Prof. Antimo Marrazzo (SISSA, Trieste).
References & links: [1] P. D’Amico et al., arXiv:2312.13708. [2] A. Zadoks, A. Marrazzo and N. Marzari, arXiv:2403.01514. For further details contact pino.damico@nano.cnr.it, arrigo.calzolari@nano.cnr.it
Title: Chiral quantum walks for quantum technologies: from storing to routing of energy and information
Tutor: Prof. Paolo Bordone, Prof. Matteo G.A. Paris (UNIMI)
Abstract: Approaching the new era of quantum information the storing and routing of energy and information is a fundamental task for all quantum processes. The objective of the research firstly relies on the optimization of the structure for storing energy and information adopting quantum methodologies to pave the way to the optimization of quantum batteries. Secondly, exploiting the bond between energy and information, the transmission of energy to different spatial regions can be interpreted as a quantum router, which is a fundamental tool in all quantum information fields. Theoretical and computational methodologies, based on a quantum walk paradigm, are used to model the structure of the quantum router or battery and combined with the application of quantum chirality allow to outperform classical procedures.
Collaborations: Quantum Technology Lab & Quantum Mechanics Group, Department of Physics, Università degli studi di Milano.
References:
1) AVS Quantum Sci. 5, 025001 (2023).
2) Phys. Rev. A 105, 032425 (2022).
3) Entropy 2021, 23(9), 1107.
4) Europhys. Lett., 67 (4), 565 (2004).
Title: Spin qubits in semiconductor quantum dots
Tutor: Prof. Paolo Bordone, Dr. Filippo Troiani (CNR)
Abstract: In the last years, the implementation of spin qubits in silicon and germanium quantum dots has been the objective of an intense international effort, involving both academic and industrial subjects. The PhD activity fits in this line of research, and specifically focuses on the simulation of hole-spin qubits in different kinds of quantum dots. Possible objectives include the investigation of the quantum gates, of the qubit readout, of the decoherence processes, or of more fundamental physical processes that determine the qubit properties (strain, Coulomb interactions). Depending also on the candidate profile, the emphasis will be placed either on the implementation and use of numerical codes, or on theoretical aspects related to solid-state physics and quantum-information processing.
Collaborations: Istituto Nanoscienze (CNR, Modena); University of Basel (Switzerland).
References:
1) Rev. Mod. Phys. 95, 025003 (2023).
2) arXiv:2312.15967 (2023).
3) Physical Review Research 5, 043159 (2023).
4) Physical Review B 107, 155411 (2023).
5) Physical Review Applied 16, 054034 (2021).
Title: Intrinsically Disordered Proteins (IDPs): Structural Characterization and Implications in Cancer Biology
Tutor: Dr. Giorgia Brancolini (CNR)
Abstract: Intrinsically disordered proteins (IDPs), which lack a conventional ordered structure, play crucial roles in cellular processes such as splicing, signaling, and transcriptional regulation. Their dysregulation is implicated in numerous diseases, including cancer.
This PhD research aims to overcome the challenges in characterizing the highly flexible and plastic structures of IDPs through innovative computational approaches. Combining cutting-edge AI predictions (such as AlphaFold) and recent advancements in CryoEM, NMR, EPR, single-molecule FRET, this study will provide new insights into IDP structure and function. Special attention is given to matrisome IDPs, key players in extracellular matrix dynamics and associated with diseases like fibrosis and cancer metastasis.
Collaborations: Prof. R. Perris (UNIPR), Prof. Pétur Orri Heiðarsson (Uni Copenhagen), Francesco Spinozzi (UNIPM).