THEMES PROPOSED FOR THE XXXV CICLE OF PhD in PHYSICS AND NANOSCIENCES (3 years starting from Nov. 2019)

PROPOSED EXPERIMENTAL PROJECTS
  • Title: Assessment of new measurement paradigms in electron microscopy.
  • Tutor: Prof. Stefano Frabboni, Dott. V. Grillo (CNR-S3)
    Abstract: This research proposal leverages the newly-acquired capacity to structure electron beams and to measure free-electron orbital angular momentum in the transmission electron microscope [1]. It involves tuning the electron probe according to the property of interest in the sample and performing post-interaction analysis over the most appropriate basis of quantum states. Applications: magnetism at the nanoscale, protein complexes recognition, plasmonic nanostructures.
    The candidate (with experimental and/or computational skills) will be part of the international research team of the Q-Sort project (FET open-01-2016-2017.1, 42 months, started October 2017. qsort.eu).
    External fellowship: available.

  • Title: Single molecule study of folding, misfolding and aggregation of proteins using Optical Tweezers.
  • Tutor: Prof. Ciro Cecconi
    Abstract: Proteins must fold into compact and unique three dimensional structures to perform their specific functions. If folding goes wrong (misfolding), proteins become useless and often harmful molecules as they aggregate into cytotoxic molecular structures. Millions of people all around the world suffer from diseases caused by protein misfolding and aggregation. In collaboration with internationally renowned scientists, in our laboratories we use Optical Tweezers to explore the folding and misfolding pathways of different proteins, and elucidate the mechanisms by which molecular chaperones interact with proteins to prevent or hinder their aggregation.
    Collaborations: Prof. S. Tans, Prof. S. Carra, Prof.Kragelund, Prof. Daniele dell’Orco.

  • Title: Hybrid spin-photon quantum circuits.
  • Tutor: Prof. M. Affronte, Dott. A. Ghirri
    Abstract: On of the objective of quantum technologies is the coherent manipulation of spins by means of microwave photons. This proposal aims at the realization of hybrid circuits where molecular spins are integrated in a superconducting microwave resonator. The experimental activity, which will be carried out in collaboration with CNR-NANO NEST Pisa and Karlsruhe Institute of Technology and L. Néel Inst in Grenoble, will be targeted at spectroscopic studies of the hybrid spin-photon system at the strong coupling regime using both continuous wave and pulsed microwave sequences.

  • Title: Charge excitations in metal/oxide nanostructures.
  • Tutor: Dott.ssa Paola Luches, Prof. Sergio D’Addato
    Abstract: The proposed work aims at the study of charge excitations in plasmonic-metal nanoparticles combined with reducible oxides. The goal is to obtain materials with increased light harvesting efficiency and with an optimized concentration of long-living excited states, which can provide charge to the environment. This aim will be achieved by addressing the time-dependent decay of excited states in systems with different composition and architecture. The work will be carried out in the framework of a PRIN project, in collaboration with the University of Bologna and with partners at large scale facilities hosting ultra-fast techniques, like ESRF, FERMI@ELETTRA, and CNR-ISM.

  • Title: Single-atoms at oxides for chemistry and magnetism.
  • Tutor: Dott.ssa Paola Luches
    Abstract: Single metal atoms represent a hot scientific topic as new stable catalysts with enhanced selectivity and specific activity, and as ultra-high density magnetic memories. The proposed work aims at the stabilization and at the study of the functionalities of single atoms combined with ultrathin oxide films. The activity includes the growth, the use of surface science techniques (e.g. STM, XPS, UPS) and of synchrotron radiation based spectroscopies (e.g. XANES; EXAFS, XMCD). The work will be carried out in a framework of national and international collaborations.

  • Title: Design and control of transparent conductive oxide for active plasmonics (EXP).
  • Tutor: Prof. Sergio D’Addato
    co-Tutor: Dott. Alessandro di Bona, Dott.ssa Stefania Benedetti
    Abstract: The proposed activity aims at the development of electrically-controlled active plasmonic systems in the VIS-IR spectral region, based on the integration of transparent conducting oxide (TCO) architectures with metal nanoparticles, making them uniquely appealing for solar cells, optical sensing, etc. TCO are obtained by doping oxides like ZnO or TiO2 , leading to a metal-like behavior at low carrier densities. This allows to extend their plasmonic response far into the infrared. The work will pursue its scope either through a careful control of doping, defect chemistry and morphology, and by active electrical gating, in strict collaboration with Italian and international partners and large scale facilities (CNR-ISM, ELETTRA, NFFA).

  • Title: Growth and functional properties of physically synthesized metal/ metal oxides core-shell nanoparticles.
  • Proposer/tutor: Prof. Sergio D’Addato
    co-Tutor: Dott.ssa Paola Luches
    Abstract: The interest in metal nanostructured films has grown in the last years because of their fascinating physical properties and their potentiality in various applications, like magnetic recording industry, catalysis and plasmonics. We propose a PhD thesis devoted to the investigation of metal and core-shell oxide-metal nanoparticles physically synthesized with a gas aggregation source which is able to produce and mass-select clusters. The study will be focused on the structure, chemical and magnetic properties of the individual particles and of the nanoparticle assembled films. Some of the techniques to be used in campus will be XPS, SEM, TEM and visible-UV Reflectivity. Part of the experimental activity will be also carried out in external facilities like synchrotrons (XAFS, PEEM and XMCD experiments), in collaboration with other groups.

  • Title: Spin transmission in chiral systems: CISS effect.
  • Tutor: Claudio Fontanesi
    Abstract: The spin transmission in chiral systems, mainly referred as chiral induced spin selectivity (CISS) effect is an area of growing interest in science [1]. Within this field, the CISS effect underlies the development of a peculiar paradigm in electrochemistry: spin-dependent electrochemistry (SDE), where measurements carried out in an electrochemical system allow to controlling spin-injection and spin-polarized currents at the electrode(chiral)|solution interface. Indeed, SDE is an effective paradigm in addressing the production and measurement of spin polarization currents in a variety of different systems, and giving the opportunity to gain further physical insight in the fundamental aspects of the influence of spin in the charge transport mechanism. i) Charge transport in organic systems grafted on inorganic surfaces like polypeptides, polythiophene, DNA, photosystem I. Remarkably, these systems are expected to behave like insulators due to the absence of free-moving p electrons, here the attention is focused in the degree of current spin polarization as a function of the organic SAM thickness ii) Also photo-electrochemical combined studies give the chance to address the mutual interplay between energy transfer and charge transfer processes as a function of spin and chirality iii) the physics underlying the enantio-selectivity process (beyond the key & lock picture).
    References: R. Naaman, Y. Paltiel, D.H. Waldeck, Chiral molecules and the electron spin, Nature Reviews Chemistry. 3 (2019) 250. doi:10.1038/s41570-019-0087-1.

PROPOSED THEORETICAL PROJECTS
  • Title: Quantum effects on electric current in new-generation memory devices through the Pauli Master Equation.
  • Tutor: Prof. Rossella Brunetti, Prof. Carlo Jacoboni (Emeritus Professor, University of Modena and Reggio Emilia)
    Abstract: The work will focus on a theoretical quantum approach to electric transport in low-dimensional amorphous chalcogenide materials based on the solution of the Pauli Master equation suitably formulated as to include the transport key features evidenced in large samples. The set of matrix equations thus obtained will be solved by means of computational techniques. The subject is very relevant for technological purposes since chalcogenide materials are already used to produce arrays of innovative memory elements. Miniaturization is a key issue and a priority, provided that some peculiar electrical properties are mantained.

  • Title: Modeling of band dispersion and contact effects for the analysis of the conduction properties of chalcogenide amorphous materials.
  • Tutor: Prof. Rossella Brunetti, Prof. Massimo Rudan (University of Bologna)
    Abstract: Conduction properties of chalcogenide materials are nowadays focus of intense theoretical and experimental research in view of their application to nanoelectronics. The existence of two high and low conduction states and the possibility of electrically switch the material between them is interpreted by means of a transport model based on the coexistence of localised and band states for carriers in the material. The simulative models for the amorphous chalcogenides developed by the research group so far need to be extended to include the Urbach tails at the band edges in order to be predictive and reliable for high-field transport. Furthermore, so far the metallic contacts are described by boundary conditions in the simulation procedure. A more accurate description of the interface is required, since it has been expermentally proven that the electric performances of the amorphous chalcogenide are very sensitive to the contact features. The proposed work will thus be focused on this goal.

    The research is performed in collaboration with experimentalists from the CNR and with the ARCES group of the University of Bologna.

  • Title: Simulation of a nanometer chalcogenide layer with graphene contacts in view of its application as selector for memory devices.
  • Tutor: Prof. Rossella Brunetti, Prof. Rita Rizzoli, Prof. Giuseppe D’Arrigo (CNR, Bologna-Catania)
    Abstract: Chalcogenide materials are good candidates for the realization of nanometer selectors, i.e., devices or structures which can control the electrical bias of another device, usually a memory element of a large array. Innovative structures designed to this purpose exploit the special properties of 2D graphene sheets used as electrical contacts in order to reduce the overall power consumption and to approach large 3D stacking configurations. The simulative models developed by the research group so far need to be extended to include the effect of graphene contacts on the high-field transport properties of amorphous chalcogenides. The proposed work will thus be focused on this goal.

    The research is performed in collaboration with experimentalists from the CNR and with the ARCES group of the University of Bologna.

  • Title: Simulating ultrafast coherent phenomena in light-harvesting complexes, as models for biosynthetic and photovoltaic phenomena.
  • Tutor: Prof. Elisa Molinari (UniMoRe)
    co-Tutor: Dott. Filippo Troiani (CnrNano)
    Abstract: The main goal of this research is to develop a microscopic understanding of the ultrafast charge separation process that takes place in model light-harvesting systems, representative of selected experimental samples that are e.g. relevant in photosynthesis or in photovoltaics. The project moves from the ab-initio description of relevant exciton and vibrational states for prototypical molecular/polymer systems. Simulations based on density functional (DFT) and many-body perturbation theory (MBPT) will provide the relevant spectra for characterizing the systems. The analysis will focus on the relation between the atomic-scale structure and the energy and nature of the excited states of relevance for photo-induced charge transfer. Data from experimental groups, especially two-dimensional electron spectroscopy (2DES), will provide validation of different ingredients. This will lead to establish a relation between the microscopic arrangement of prototypical organic structures and quantum coherences observed by 2DES, opening the way to a more rational design of artificial materials for photovoltaic applications.
    The second part of the project will explore the use of entanglement measures as a unifying quantitative characterization scheme for spatial coherence in the system eigenstates, as well as degree of coherence in the system dynamics (through the off-diagonal elements of the density matrix in the excitonic manifold). Entanglement will also be used to quantify the mixing between electronic and vibrational degrees of freedom in the system eigenstates (static vibronic coherences), especially in systems where such mixing is suspected to significantly contribute to the creation and preservation of the observed dynamical coherences.

    This research is part of an international collaboration on “Multiphoton Microscopy and Ultrafast Spectroscopy: Imaging meets Quantum”, which includes leading academic and industrial teams in 9 European countries and offers ample opportunities of international training and visits (see MUSIQ).
    Important note: Students who have not leaved in Italy for more than 12 months in the last 3 years may be eligible for a reserved fellowship on this topic, supported by the MUSIQ Marie Curie European Training Network. This European scheme implies special conditions and eligibility requirements. A separate application must be submitted.

  • Title: Excitonic insulator in two-dimensional long-range interacting systems.
  • Tutor: Prof. Elisa Molinari (UniMoRe)
    co-Tutor: Dott. Massimo Rontani (CnrNano), D. Varsano (CnrNano)
    Abstract: This project addresses the possibility to realise an `excitonic insulator’ (EI), the long-sought state of matter resulting from spontaneous formation of bound electron-hole pairs ---excitons--- expected when their binding energy exceeds the band gap. Fueled by the intriguing analogy with the Bardeen-Cooper-Schrieffer superconductor, the search of the EI has so far been hindered by the lack of materials with sufficient exciton binding, which in most systems scales with the gap size due to screening.

    The project aims at demonstrating that the EI phase can be realized in two-dimensional (2D) systems where long-range Coulomb interaction is found to be virtually unscreened, and exciton binding is strongly enhanced. It will combine high-level first-principles calculations (many-body perturbation theory) and self-consistent mean-field approaches, and will address 2D candidate materials selected in collaboration with leading experimental groups.

    The research is part of a National project, EXC-INS, coordinated by the Modena team, which includes SISSA, the University of Trieste and the CNR units in Modena and Politecnico di Milano. Close collaboration is planned with the MaX European Centre of Excellence (www.max-centre.eu), involving leading international teams in computational materials design: EPFL Lausanne (N. Marzari), ICN2 Barcelona (P. Ordejon), SISSA Trieste (S. Baroni), FHZ Juelich (S. Bluegel), CEA Grenoble (T. Deutsch), with ample opportunities for visits and collaborations.

  • Title: Friction at the nanoscale (EXP).
  • Tutor: Prof. Sergio D’Addato; Dott. Guido Paolicelli (CNR-NANO)
    Abstract: Friction, wear and adhesion properties of materials are strictly related to a number of chemical and physical processes occurring at their surfaces. In this context the prosed activities are oriented to especially to nanoscale problems mainly explored by scanning probe microscopy (AFM-STM). Projects actually running explore very fundamental effects like sliding friction on a substrate undergoing phase transition (surface melting or a substrate exhibiting a rotational transition as fullerite) or aim at understanding solid lubricant coating based on graphene an others 2D lamellar structures eventually also in the form of self-assembled nanostructures (nanoscrolls). Finally the influence of morphologically modified surfaces on the tribology response of materials is a topic of our interest.

    External fellowship: available in the framework of the project MIUR-PRIN 2019-2022 “Understanding and Tuning FRiction through nanOstructure Manipulation” (UTFROM).

  • Title: Multiscale modeling of HfO2 stack for memory application devices.
  • Tutor: Prof. Elena Degoli, Prof. Stefano Ossicini
    Abstract: We propose to study the physical mechanisms governing the charge transport through HfO2 stacks (considering possible interfaces, grain boundaries and defects) using a multiscale modeling approach which merges semiclassical and ab initio calculation in density functional theory. This will permit to interpret the reliability and electrical characteristics of logic and memory devices. The work will be done in collaboration with Dr. Luppi Dr. and Capron (from the Laboratoire de Chimie Théorique and Laboratoire de Chimie Physique Matière et Rayonnement of the Sorbonne Universitè Paris France, respectively). It is also active a collaboration with Prof. L. Larcher currently at the Applied Materials company.

  • Title: A worldline approach to the computation of tree-level and one-loop scattering amplitudes in curved spaces.
  • Tutor: Prof. Olindo Corradini
    Abstract: The worldline formalism is a powerful technique to the computation of scattering amplitudes and effective actions in the presence of external fields. Although the method is still relatively unexplored in generically curved spaces—i.e. when gravitons are present even as external particles—some preliminary results, involving scalar fields, have been recently found by our group, and they provide a promising starting point towards foreseen generalizations.
    External fellowship: no. Association to INFN, Sezione di Bologna.
    Collaboration: Fiorenzo Bastianelli (UniBo), Christian Schubert and collaborators (Universidad Michoacana, Mexico)

  • Title: Coherent manipulation of molecular toroidal states in hybrid spin-photon quantum circuits.
  • Tutor: A/Prof. A. Soncini (Uni. Melbourne) and Prof. M. Affronte (Uni. Modena)
    Abstract: we propose to study quantum effects in hybrid quantum devices made of maolecular spins. Coherent manipulation of spin degrees of freedom in molecular spins via microwave photons is a promising route to the development of quantum technologies based on molecular devices [1,2]. This proposal aims to study molecular spin rings displaying vortex magnetic quantum states called toroidal moments [3], integrated in a superconducting microwave resonator. By virtue of the spin-chirality of toroidal states [4], such molecular quantum states are predicted to display enhanced magneto-electric coupling [4,5]. The aim will be to optimize protocols for the coherent manipulation of toroidal moments in molecular nanomagnets using hybrid experimental and theoretical approaches, involving the development of theoretical models and ab initio methods at the University of Melbourne, and direct experimental implementation and probe of the proposed devices at the UNIMORE.
    [1] Sci. Rep. 2017, 7, 13096.
    [2] J. App. Phys. 2018, 124, 194501.
    [3] Phys. Rev. B (R) 2008, 77 220406; Angew. Chem. Int. Ed. 2008, 47, 4126.
    [4] Phys. Rev. B 2018, 98, 094417.
    [5] Nature Comm. 2017, 8, 1023.

  • Title: Advanced material for synaptic electronics and neuromorphic computing.
  • Tutor: Dott. Arrigo Calzolari
    Abstract: Inspired from the power efficiency of human brain, synaptic electronics and neuromorphic computing recently emerged as top candidates to reduce power consumption of big data analysis and perform robust and fault-tolerant computation. The development of new electronics requires the engineering of emerging nanodevices (e.g. 3D integrated memories, selectors) and the characterization of the constituent materials (e.g. ovonic threshold materials, phase change materials, ferroelectric metal oxides) at device level, including the effect of defects, impurities, and boundaries that – e.g. for synaptic electronics - play a crucial role in the definition of the material itself. Quantum mechanical modelling can efficiently contribute to this process. This theoretical thesis deals both with the application of state-of-the-art packages for DFT material simulations and with the development of original solutions for the analysis of the electronic structure and energetics of disordered systems. This project will also benefit from the direct collaboration with European experimental groups.

  • Title: Plasmonics in stacked 2D materials for nanophotonics and metamaterials.
  • Tutor: Dott. Arrigo Calzolari
    Abstract: By using complementary first principles and effective medium techniques this thesis will investigate the combined effect of spin-orbit coupling, electron-electron correlation and van der Waals interactions on the optical and plasmonic properties of stacked 2D materials. This class of materials exhibits a highly spatial anisotropy of the optical properties, which derives from the not-trivial interband and intraband transition pattern at reduced dimensionality. This may characterize stacked 2D systems as natural hyperbolic metamaterials, that exhibit a unique variety of plasmonic excitations (namely surface plasmons, Dirac plasmons, and Dyakonov plasmons) that covers the wide range of frequencies from THz to UV-vis and that makes them suited for optoelectronic devices (e.g. hyperbolic waveguides, superlences) working in the sub-wavelength regime. This work will be done in collaboration with experimental and theoretical groups in Europe and US.

  • Title: Time-dependent dynamics of correlated carriers for quantum computing.
  • Tutor: Prof. Guido Goldoni, Dott. Paolo Bordone, Dott. Andrea Bertoni
    Abstract: The correlated dynamics of few interacting quantum particles leads to renormalized scattering coefficients and quantum entanglement. The proposed activity will approach the very fundamental problem to simulate the time-dependent dynamics of two or few Coulomb-interacting particles by (i) the exact numerical solution of the time-dependent few-particle Schrödinger equation (in principle always possible, but requiring the use of massively parallel computers and limited to few degrees of freedom, e.g. 1D systems), and (ii) the development, validation and application of new self-energy methods. Such beyond-mean-field methods retain the fundamental dynamical process of the quantum complex (say and electron-hole pair) but are orders-of-magnitude less CPU-intensive and can be exploited in nano-device engineering as well as in extensive fundamental studies. The developed methods will be applied to simulate semiconductor quantum nano-devices where information is processed either i) by spatially indirect excitons or ii) by hot electrons propagating in quantum Hall edge channels. We particularly intend to assess the potentiality of such systems as platforms for quantum computing devices. The present theoretical-computational simulative activity will be carried in collaboration with experimental partners. Working in this very innovative, world-connected field of research, the PhD fellow will acquire a working knowledge in advanced modelling of nano-materials, basics of quantum science for next-generation information technologies, and the latest high performance computational techniques required to write software exploiting massively parallel architectures.
    References: Phys. Rev. B 93, 195310 (2016); Phys. Rev. B 94, 125418 (2016); Phys. Rev. B 97, 205419 (2018).

  • Title: Core-shell nanowires: nano-materials for the next generation nano-opto-electronics.
  • Tutor: Prof. Guido Goldoni, Dott. Andrea Bertoni
    Abstract: Core-shell nanowires are innovative nano-materials, similar to long nano-needles where material modulations, both along and radially to the axis, allow to tailor their electronic properties to a high degree, opening to a wide range of application in nano-opto-electronics. At the same time, the electronic system is confined to new topologies, which also opens to new quantum phenomena. This thesis will focus on the fundamentals of the electronic states of these nano-materials, with an emphasis on their spin and thermo-electric properties, specifically addressing ongoing experimental activities. The activity is of a theoretical/computational character. The candidate will acquire a working knowledge in advanced modelling of nano-materials and simulative methods in quantum nano-devices, as well as latest high performance computational techniques required to write software exploiting massively parallel architectures.
    References: Nano Lett. 13, 6189 (2013); Nano Lett. 14, 2807-2814 (2014) ;Nanotechnology 27, 195201 (2016).

  • Title: Self-interaction and reference results from many-body perturbation theory: a diagrammatic approach.
  • Tutor: A. Ruini (UniMoRe)
    co-Tutor: A. Ferretti (CnrNano), D. Varsano (CnrNano)
    Abstract: The concepts of self-interaction and total energy piece-wise linearity have been linked together and recently extensively used to assess e.g. the quality of exchange-correlation approximations in density functional theory. We here propose to follow the same route to characterize advanced electronic structure methods arising from many-body perturbation theory (e.g. GW, SOSEX, second-Bohr approximations), with special emphasis on beyond-GW and vertex-corrected methods. While doing so, reference results will be produced for selected systems. This thesis work will be both theoretical and computational, with the latter aspect very central in the research activity of the candidate.
    Collaborations: Prof. N. Marzari’s group at EPFL, Lausanne, CH.

  • Title: Ab-initio design of graphene-based nanomaterials for quantum technologies.
  • Tutor: A. Ruini (UniMoRe)
    co-Tutor: D. Prezzi (CnrNano)
    Abstract: Single organic molecules have been recently exploited to create hybrid quantum devices [1], with the molecules working at the interface of waveguides and nanocavities, or embedded in nano-electronic circuits and nano-mechanical devices. We here propose to exploit the predictive capabilities of ab-initio calculations (DFT-based as well as beyond mean-field approaches), eventually in combination with high-throughput engines, to design graphene-based nanosystems with targeted properties that are optimized to develop specific functionalities. This thesis work will have an essentially computational character, and a close collaboration with world-renowned experimental groups is forseen.
    [1] See e.g. Photostable Molecules on Chip: Integrated Sources of Nonclassical Light, P. Lombardi et al, ACS Photonics (2018) 5, 126; Self-Assembled Nanocrystals of Polycyclic Aromatic Hydrocarbons Show Photostable Single-Photon Emission, S. Pazzagli et al., ACS Nano (2018)12, 4295.
    Collaborations: Costanza Toninelli (CNR-INO, Florence); Jean-Sebastien Lauret (CNRS, Saclay).

  • Title: Designing Novel Materials and Processes to Reduce Friction.
  • Tutor: Prof. M. Clelia Righi
    co-Tutor: Prof. Mauro Ferrario
    Abstract: Friction and wear are common phenomena that result in massive economic and environmental costs. Our group (see tribchem) collaborates with the most active tribology laboratories worldwide, as Imperial College London and Argonne National Lab Chicago, and with industries, as Total and Toyota, to identify new materials and processes to reduce friction. Here the project is to learn and apply different computational methods, as classical and ab-initio molecular dynamics, high throughput screening, and multiscale approaches to study lubricant additives, special molecules included in engine oils, and solid lubricants, i.e., 2D materials such as graphene and MoS2
    A further scope of the project is to provide novel understanding on the use of mechanical forces to promote chemical reactions, with application in catalysis.
    The activity will involve a collaboration with the industry Total S.A. .
    Fellowship: Possible.

  • Title: Advancing Material Interfaces with (Multiscale) Modelling.
  • Tutor: Prof. M. C. Righi
    co-Tutor: Prof. Mauro Ferrario
    Abstract: Interfaces play an essential role in virtually all materials and devices. First principles calculations allow for an accurate description of the chemical interaction between two surfaces, or between a liquid and a surface. Our group (see tribchem) has recently developed a workflow to automatically model solid interfaces and calculate their adhesion and resistance to sliding from first principles. The project here is to perform high throughput screening of additional mechanical and electronic properties of material interfaces. The collected data will allow us to identify general trends and serve as input parameters for large scale models. The latters will be developed in collaboration with the Imperial College, London.
    Fellowship: Possible.