Doctoral School

Reading date: 02/09/2024

• LUQUE MERINO, RAFAEL: Optoelectronic studies of strongly correlated 2D materials
  
  Author: LUQUE MERINO, RAFAEL
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN PHOTONICS
  Department: Institute of Photonic Sciences (ICFO)
  Mode: Normal
  Deposit date: 13/06/2024
  Reading date: 02/09/2024
  Reading time: 11:00
  Reading place: ICFO, Mediterranean Technology Park, Avinguda Carl Friedrich Gauss, 3, 08860 Castelldefels, Barcelona
  Thesis director: EFETOV, DMITRI K.
  Committee:
       PRESIDENT: POCCIA, NICOLA
       SECRETARI: KOPPENS, FRANK
       VOCAL: TÖRMÄ, PÄIVI
  Thesis abstract: The study of strongly-correlated matter in two-dimensional materials has emerged as a exciting prospect for the exploration of condensed matter physics, as well as the design of novel device platforms. Moiré engineering , where the 20 layers feature an interlayer twist angle, has proven to be a powerful tool to engineer electronic correlations . In magic angle twisted bilayer graphene, a twist angle of 1.1° between the graphene layers generates a moiré superlattice potential. A flat electronic band appears at the Fermi level, in which a variety of interaction-driven , many-body quantum phases can emerge . Another avenue to study strong electronic correlations in two dimensions is the exfoliation of intrinsically correlated bulk crystals into the atomic limit.The optoelectronic study of strongly-correlated systems in 20 heterostructures stands out as a powerful probe, as it can provide insight into both the electronic transport properties and the fundamental light-matter interaction in these systems . In this thesis , we study two strongly correlated 20 materials: MATBG and the cuprate superconductor Bi2Sr2CaCu208-delta (BSCC0-2212). We leverage different optoelectronic techniques to study the fundamental properties of the correlated electrons in the MATBG flat bands and the potential of two-dimensional BSCC0-2212 layers for applications in quantum sensing .First, we investigate the electronic spectrum of the MATBG flat bands through the study of their thermoelectric transport . We use an optical excitation to induce a thermal gradient, which in turn generales a charge curren!. We report anomalous thermoelectricity which provides strong evidence for the coexistence of localized and de-localized electronic states in the strongly-interacting flat bands.Next, we study the dynamics of hot carrier cooling in the MATBG flat bands using a frequency-resolved photomixing technique . Strikingly, we find that hot carriers can efficiently relax their energy down to cryogenic temperatures ; in contras! to the case of bilayer graphene samples . We propose a novel Umklapp electron-phonon scattering mechanism for hot carriers in MATBG, enabled by the moiré superlattice potential.Lastly, we explore the development of superconducting photodetectors with high-T_c based on ultrathin BSCC0-2212 flakes . We fabricate high quality samples that exhibit remarkable performance at telecom wavelengths . We observe fast and sensitive bolometric response at T = 77 K in free-space and waveguide-coupled devices , as well as single-photon sensitivity at T = 20 K through a non-bolometric , avalanche detection mechanism .
  

Reading date: 03/09/2024

• LOZANO HERNÁNDEZ, NEKANE: Microtexturization of liquid silicone rubber surfaces by injection moulding
  
  Author: LOZANO HERNÁNDEZ, NEKANE
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN POLYMERS AND BIOPOLYMERS
  Department: Department of Chemical Engineering (EQ)
  Mode: Normal
  Deposit date: 29/05/2024
  Reading date: 03/09/2024
  Reading time: 11:00
  Reading place: Sala Polivalent de l'Edifici I, Edifici I, planta baixa, Campus Diagonal-Besòs
  Thesis director: PUIGGALI BELLALTA, JORGE | DEL VALLE MENDOZA, LUIS JAVIER
  Committee:
       PRESIDENT: RODRÍGUEZ FERNÁNDEZ, ISABEL
       SECRETARI: CASELLAS PADRO, DANIEL
       VOCAL: TYLKOWSKI, BARTOSZ
  Thesis abstract: Nature is in continuous change and evolution in response to environmental shifts. That is because different micro- and nanotextures have emerged on some plant leaves or insect skins. These surface patterns enable them to possess advanced surface properties. Some examples include the superhydrophobic and self-cleaning leaves of the lotus plant, or the dry adhesion found on gecko feet. There has been a strong trend in recent years to transfer these surface textures to industrial applications to replace various coatings currently in use. The development of transformation technologies and the extensive knowledge of materials developed in recent decades have allowed for the extension of materials onto which these microtextures can be replicated.In the case of Liquid Silicone Rubber (LSR), studies on replication focus on laboratory-scale technologies that allow for high replication but low production throughput. However, these materials possess properties of great interest and can have many synergies with microtexturing: good biocompatibility for use in medical devices, weather resistance for self-cleaning or superhydrophobic surfaces, or good mechanical and chemical resistance that can extend the lifespan of microtextures on the surface. In order to extend studies on replication techniques of microtextures on liquid silicone surfaces, this thesis has been developed focusing on replication through injection of microtexturized inserts. There have been some previous works on replication using this technology; however, they fail to achieve good demolding or uniform textures in height due to the use of textured metallic inserts. Therefore, this thesis proposes the use of textured films to facilitate demolding due to the flexibility of the film.This thesis is divided into two main parts: The first part consists of the development of tools and technology for the replication of liquid silicone parts by injection. Firstly, optimization is carried out on the manufacture of textured films by nanoimprint lithography to withstand the injection conditions of this material. After this initial optimization and with the manufacturing of the necessary tools, a study and optimization of different part geometries for the different studied microtextures (pillars, lines, and holes ranging from 1 to 50 microns) are conducted. The second part of the thesis consists of an extensive study of different advanced surface properties due to microtexturing. This includes properties such as surface wettability or roughness studies, as well as different studies of part durability for the application of different mechanical stresses. Additionally, emphasis is placed on the study of biological properties, of interest in the medical sector. The studies focus on the variation of cellular growth and adhesion due to the presence of microtextures. Based on all the results obtained, a use case of an optogenetic implant is proposed.From the results obtained, it can be concluded that the replication method proposed and developed in this thesis is an optimal method for industrial scaling of these microtextures in liquid silicone. Not only because of its high production throughput but also because of the versatility of part geometries and microtextures it allows. This versatility of microtextures enables the acquisition of a wide range of surface properties of high interest at an industrial level. Particularly in the case of the medical sector, where a use case of a microtexturized implantable device with this technology has been demonstrated, which could be extendable to other applications.
  

Reading date: 05/09/2024

• BALANZÓ JUANDÓ, MARIA: Certification in quantum information theory: key distribution, self-testing and entanglement
  
  Author: BALANZÓ JUANDÓ, MARIA
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN PHOTONICS
  Department: Institute of Photonic Sciences (ICFO)
  Mode: Normal
  Deposit date: 10/07/2024
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: ACÍN DAL MASCHIO, ANTONIO | FARKAS, MÁTÉ
  Committee:
       PRESIDENT: TURA I BRUGUÉS, JORDI
       SECRETARI: ARGÜELLO LUENGO, JAVIER
       VOCAL: MANCINSKA, LAURA
  Thesis abstract: In the beginning of the last century, we witnessed a change of paradigm in how physics described the world with the formulation of quantum mechanics. This new theory shook the pillars of science by setting fundamental limits on our ability to describe nature. It was able to explain the laws that govern physics at the microscopic level, which could not be explained by means of the existing laws. The behavior at such small scales differs significantly from our daily experience. For instance, exotic phenomena such as entanglement or nonlocality are exclusively observed at the microscale. Entanglement and nonlocal correlations represent two essential resources in quantum information processing, enabling novel tasks that are unattainable within a classical framework.The end of the twentieth century has seen a wave of studies on the fundamental properties of quantum theory. Nowadays, as a consequence of these advances in quantum theory and experiments, various companies are selling devices claimed to perform a quantum information task with no classical analog, such as quantum random number generators, prototypes of quantum computers, or quantum key distribution devices. Since quantum devices cannot be simulated classically, it is hard to verify them using only classical resources, which are the ones available to the average user. Hence, a natural question to ask ourselves is how we can verify the properties and functioning of quantum devices in an efficient way.In this context, device-independent protocols have been developed in quantum information theory over the past decade. The main advantage of such protocols is that users do not have to make any assumption about the inner workings of their devices, considering them as black boxes. The security and success of a device-independent protocol relies on the observation of nonlocal correlations in a Bell experiment. This thesis is dedicated to provide tools to achieve the certification of quantum information devices or tasks in a device-independent way.In the first part of this thesis, we focus on certifying the security of device-independent quantum key distribution. To this end, we first study whether Bell nonlocality is a sufficient condition for security in the most used protocols, proving that there exist nonlocal correlations that are not useful for secure device-independent quantum key distribution using these protocols. Moreover, we study noisy scenarios, that is when experimental imperfections are present, and derive upper bounds on the two-way and one-way key rates for this kind of protocols.In the second part, we study self-testing, which is one of the simplest device-independent protocols. Its goal is to recover quantum states solely from the observed measurement correlations. In the majority of quantum information processing tasks one needs to consider a particular quantum state, making the certification of quantum states of great importance in the device-independent paradigm. We prove that all multipartite states of qubits can be self-tested. Moreover, we study self-testing in higher-dimensional systems.Finally, in the third part of this thesis, we tackle the problem of certification of entanglement. It is well known that certifying the presence of entanglement in a system is a hard task. The key methods for entanglement detection, entanglement witnesses and positive maps, rely on our understanding of the mathematical features of multilinear algebra. By using the fact that any separable state is one to one related to a matrix inequality, we port previously known results on the entanglement of states with positive partial transpose into the domain of matrix inequalities, which also allow us to translate multilinear positive maps back into entanglement witnesses. This approach leads to a unified treatment of a large class of matrix inequalities, allowing us to find new inequalities on the basis of advances in entanglement theory.
  

• CAÑÓN RODRÍGUEZ, DORA: Aporte a la construcción de comunidades sostenibles. Un modelo para analizar su sostenibilidad
  
  Author: CAÑÓN RODRÍGUEZ, DORA
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SUSTAINABILITY
  Department: University Research Institute for Sustainability Science and Technology (IS.UPC)
  Mode: Normal
  Deposit date: 12/07/2024
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: ALVAREZ DEL CASTILLO, JAVIER | RÍOS OSORIO, LEONARDO ALBERTO
  Committee:
       PRESIDENT: ROCA ROSELL, ANTONI-MARIA CLARET
       SECRETARI: LAVIÑA GÓMEZ, FRANCISCO JAVIER
       VOCAL: TORO CALDERÓN, JOSÉ JAVIER
  Thesis abstract: This thesis developed an understanding of what makes a community sustainable, its particular characteristics, the values it shares, its way of life and its interaction with natural systems. It categorized the concept of sustainable communities as a complex and adaptive socio-ecological system, with characteristics of socio-ecological resilience. The study focused on the structural and functional factors or elements that directly and indirectly condition and influence the life of people and the social systems that constitute them. Thesis addressed a real case study represented in the rural dairy community of Monquentiva in the Páramo de Guatavita, Colombia, as an empirical element on which the research was built. The main objective was to establish the characteristics of a theoretical model for analyzing the sustainability of a community that will shape the behavior of the social-ecological system and the factors that can affect its sustainability.By applying systems theory, the rural community was studied as a complex and adaptive socio-ecological system, emphasizing the interactions between human and non-human actors (ecological entities) and not between variables or systems (sociological phenomena). Two methodological proposals were adapted to develop the doctoral research, the first being the prospective analysis and the second the action situation framework. The action situations framework and its underlying conceptualization of SES were structured based on understanding SES resilience thinking as complex and tightly intertwined adaptive systems. The information obtained with the active participation of community stakeholders at different levels of the system was graphically represented in a theoretical model to account for the characteristics that condition the sustainability or unsustainability of the system, its social-ecological resilience, the coordination among the system of stakeholders, and the responses assumed to face emerging phenomena that can lead the community to either adapt or transform. It was concluded that the model is appropriate to describe and analyze the organization and functioning of the system of actors of the SSE dairy cattle community of Monquentiva and its resilience characteristics such as modularity, diversity, feedback mechanisms, efficiency and resources that favor social-ecological resilience. The model provides information about the current context of the community and their main productive economic activities, helps to know where to target interventions and build resilience. It should be seen as a contribution to the observation of resilient socio-ecological systems, has the potential to contribute to broader sustainability models for rural SSE, and can inform strategic adaptation planning in the face of different shocks and socio-ecological dynamics specific to rural spaces.
  

• LUCAS ROJAS, LUIS JOSE: Análisis de la direccionalidad en la respuesta de suelo
  
  Author: LUCAS ROJAS, LUIS JOSE
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS
  Department: Department of Civil and Environmental Engineering (DECA)
  Mode: Normal
  Deposit date: 10/07/2024
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: CASELLES MAGALLON, JOSE ORIOL | SALINAS NAVAL, VICTOR
  Committee:
       PRESIDENT: LUZÓN MARTÍNEZ, FRANCISCO
       SECRETARI: MUJICA DELGADO, LUIS EDUARDO
       VOCAL: TAPIA JIMÉNEZ, MARÍA DEL MAR
  Thesis abstract: A problem subjected to multiple researches and currently still is focuses on accurately characterizing the dynamic response ofthe soil when an earthquake occurs. When an earthquake occurs, the seismic signal is modified due to the geological (soilresponse) and topographic conditions of the terrain, phenomena known as site effect. The ground response is mainly showedwhen the seismic signal is amplified at some frequencies due to impedance contrasts under the affected area. Environmentalvibration or microtremors have provided decisive information to become an important source in seismology contributing todetermine the predominant frequency of the soil response, allowing more exhaustive analyzes and greater precision on thegeological and geotechnical conditions of subsoils in densely populated urban areas. The use of microtremor records toestimate the ground response have some advantages, among which highlight the ease of recording and the possibility ofdetermining the predominant frequency of the ground seismic response without earthquake occurrence. The main objective ofthis work is analyzing and evaluating, using techniques and procedures typical of circular statistics, the angular behavior ofenvironmental vibration records, examining whether the direction of the soil response is affected by the presence of suddenlateral geological changes. In the first instance, through descriptive circular statistics procedures, it is quantified and graphicallyrepresented the measures of central tendency and dispersion. Secondly, using techniques and methods typical of inferentialcircular statistics, it is analyzed whether the angular samples extracted from in situ measurements show directional changes inthe soil response caused by the presence of lateral geological variations in the subsoil. Finally, using linear and circularstatistical techniques, it is determined the correlation between two of the circular variables, establishing whether a predictivemodel is viable. In addition, it is defined some pattern of directional behavior of environmental vibration in soils with lateralheterogeneity.