# Research

### Devices and Sensors

### Equilibrium and Non-equilibrium Critical Phenomena

### Theoretical and Experimental Biological Physics

### Production and Characterization of Thin Films, Composites and New Materials

### Complex Systems

### Magnetic Systems and Nanostructured Magnetic Materials

### Devices and Sensors

#### Production and characterization of devices and sensors (experimental)

The techniques of optical lithography, plasma corrosion and chemical corrosion have been applied in the production of devices based on thin films, polymers, two-dimensional and nanostructured materials. Such devices have been applied in the study in the production of biosensors, magnetic field sensors, magnetic memories, X-ray and Gamma-ray sensors, solar cells, optical memories, batteries and electrodeposited capacitors.

The devices and sensors have been produced by epitaxial growth, electrodeposition, photoinduced electrodeposition, ion milling, spin coating, mechanical exfoliation and sputtering growth techniques. Characterizations are performed:

Optics: Raman spectroscopy, photoluminescence spectroscopy, static and dynamic light scattering, optical profilometry and magneto-optical Kerr spectroscopy.

Electric characterizations and magnetotransport: Electric transport measurements under magnetic field and in cryostat with variable temperature up to 10 K. Currently, the characterizations include measurements of magnetoresistance, Hall effect, DC / AC susceptibility and resistivity.

**Professors:**

Eduardo Nery Duarte de Araújo

Joaquim Bonfim Santos Mendes

### Equilibrium and Non-equilibrium Critical Phenomena

#### Interface aggregation and growth phenomena (theoretical)

Simulations, experiments and scale analyzes of the dynamics of kinetic aggregation processes are carried out here, with emphasis on the growth of self-organized nanostructures, epitaxial films, electrodeposition and propagation in porous media. In addition, a theoretical study is made of the mapping of equilibrium and far-equilibrium models in self-related interfaces.

**Professors:**

Silvio da Costa Ferreira Junior

Tiago José de Oliveira

#### Dynamic processes in complex networks (theoretical)

Studies of dynamic processes in complex networks are proposed and analyzed by analytical and computational methods. The dynamics of epidemic propagation is investigated in random (free of scale, small world, etc.) and real networks, including analysis of the spread of vector-borne diseases and in metapopulations. Models for forming opinions, spreading rumors and critical phenomena, in general, are also objects of study in complex networks.

Professor:

Silvio da Costa Ferreira Junior

### Theoretical and Experimental Biological Physics

#### Experiment (experimental)

Optical tweezers and applications in the handling of “unusual” materials

This line aims to advance in the physics of optical manipulation of microsystems and, in particular, to develop new applications for the technique of optical tweezers. We also study the behavior of unusual materials, such as topological insulators and semiconductors, in an optical tweezers. Several complementary optical techniques are used together: dynamic light scattering, videomicroscopy and digital image analysis, etc. Microfluidic applications are also of interest to us. This line involves both experiment and theory.

Professor:

Márcio Santos Rocha

#### DNA-ligand Interactions (experimental)

This line aims to elucidate and characterize the interactions of the DNA molecule with several types of ligands, such as drugs and proteins. For this, we use techniques such as optical and magnetic tweezers, atomic force microscopy, light scattering, gel electrophoresis, among others. The mechanisms of action of classic chemotherapeutic drugs are elucidated here at the molecular level. New developed drugs (potential therapeutic agents) are also being tested. We also study the physics of chromatin and the action of various drugs on condensed DNA.

**Professor:
**Márcio Santos Rocha

#### Instrumentation for experiments with single molecules (experimental)

This line aims to develop and implement new techniques for manipulation and characterization of single molecules at the UFV Biological Physics Laboratory, such as holographic optical tweezers and hybrid optomagnetic tweezers. The focus is to apply new techniques in studies with biomolecules and new materials. We also work on new methods of calibration and characterization of measurements obtained with these techniques.

**Professor:**

Márcio Santos Rocha

#### Dynamics of cellular processes and formation of supracellular structures

This line of research involves experiments related to cell membrane activity, migration and aggregation of cells in culture and interaction dynamics of biological macromolecules (adhesion structures, ligand-receptors) using techniques of videomicroscopy, electron microscopy and probe scanning, optical tweezers and molecular biology. The results are analyzed by analytical techniques and computer simulations.

**Professor:**

Marcelo Lobato Martins

#### Population dynamics (theoretical)

Mathematical models for agricultural pests are constructed and analyzed by analytical methods (dynamic systems theory) and computational methods (simulation of cellular automata and numerical integration of EDOs / EDPs). Processes of biological invasion mediated by allelopathy, insect dispersion guided by pheromones and trophic web dynamics are examples studied based on models of multiple scales

**Professors:**

Marcelo Lobato Martins

Silvio da Costa Ferreira Junior

#### Mathematical oncology (theoretical)

In this study we propose mathematical models of multiple scales for the growth of tumors and the effect of anti-cancer therapies. In them, the microscopic (molecular) and mesoscopic (cellular) scales are described by stochastic cellular automata with transition probabilities determined by local concentrations of continuous fields (nutrients and growth factors – macroscopic scale). The results can be compared with histopathological patterns, spheroids and tumors induced in animals.

Professors:

Marcelo Lobato Martins

Silvio da Costa Ferreira Junior

### Production and Characterization of Thin Films, Composites and New Materials

#### Epitaxial growth (experimental)

Epitaxial growth and characterization of thin films and quantum dots based on compounds II-VI are performed. The hot wall epitaxy technique is used for growth. The Physics Department recently acquired a sputtering growth system, which allows the manufacture of heterostructures and devices based on the deposition of thin metallic, magnetic, semiconductor and insulating films. The characterization is performed by the following techniques: X-ray diffraction, optical transmission, electrical characterization, profilometry and AFM.

Professors:

Clodoaldo Irineu Levartoski de Araújo

Eduardo Nery Duarte de Araújo

Joaquim Bonfim Santos Mendes

Leonarde do Nascimento Rodrigues

Sérgio Luis de Abreu Mello

Sukarno Olavo Ferreira

#### Roughness measurements in thin films (experimental)

This work aims to determine the exponents of roughness and growth to investigate the growth dynamics in thin films and quantum dots from the analysis of profilometry measurements and atomic force microscopy.

**Professors:**

Sukarno Olavo Ferreira

Tiago José de Oliveira

#### Nanostructured materials (experimental)

Manufacture of nanostructured materials using different synthesis techniques: semiconductor colloidal quantum dots, metallic nanoparticles, luminescent nanostructures (polymer dots, carbon dots).

Study of the properties and interaction of radiation in nanostructured materials and / or nanocomposites by means of steady state photoluminescence and resolved in time.

**Professors:**

Andreza Germana da Silva Subtil

Eduardo Nery Duarte de Araújo

Mariana da Costa Novo Pimenta Brandão

#### Generation and detection of pure spin currents in magnetic devices (experimental)

Investigation of phenomena that explore manipulation and transport of spin in hybrid devices consisting of ferromagnetic and non-magnetic materials, with emphasis on the effects of generation and detection of pure spin currents in conventional magnetic films and new materials, such as: graphene, disulfide molybdenum, topological insulators, organic polymers and Weyl semimetals. The generation of spin currents is performed by excitation with microwaves (spin pumping) and also by thermal effects (Seebeck spin effect). In turn, the detection of spin currents can be by the inverse spin Hall effect and also by the inverse Rashba-Eldeinstein effect.

**Professor:**

Joaquim Bonfim Santos Mendes

### Complex Systems

#### Microfluidics (experimental)

Low size variation emulsions are produced by pumping fluids in microchannels. This technique is being used for the preparation of magnetizable emulsions for the study of the aggregation of these emulsions with the application of homogeneous magnetic fields and also for the preparation of double emulsions.

**Professor:**

Álvaro Vianna Novaes de Carvalho Teixeira

#### Dynamic processes in complex networks (theoretical)

Studies of dynamic processes in complex networks are proposed and analyzed by analytical and computational methods. The dynamics of epidemic propagation is investigated in random (free of scale, small world, etc.) and real networks, including analysis of the spread of vector-borne diseases and in metapopulations. Models for forming opinions, spreading rumors and critical phenomena, in general, are also objects of study in complex networks.

**Professor:**

Silvio da Costa Ferreira Junior

#### Micro-rheology of viscoelastic materials (theoretical)

From theoretical-computational approaches based on micro-rheology, we seek to elucidate the relationship between the macroscopic mechanical response of viscoelastic materials (eg, hydrogels and collagen) from microscopic interactions between their fundamental constituents, for example, flexible filaments (eg, polyelectrolytes ) and semi-flexible filaments (eg, fibrils, actin, virus, DNA, fribrin, etc.). The main idea is to develop theoretical models based on the results obtained from multi-scale computer simulations that use Brownian dynamics methods.

**Professor:**

Leandro Gutierrez Rizzi

#### Nucleation in disordered systems (theoretical)

Theoretical and computational studies on the phenomena of nucleation and particle aggregation in biomolecular and quasicrystalline systems. Computer simulation developments include simulation methods for out-of-balance systems such as kinetic Monte Carlo. In addition, we evaluate alternative theoretical approaches to the Classic Theory of Nucleation, since it cannot be applied to the studied systems.

**Professor:**

Leandro Gutierrez Rizzi

#### Phase transitions in frustrated magnetic systems (theoretical)

Development of computer simulations based on advanced Monte Carlo algorithms to study the thermostat of low-dimensional magnetic materials that have frustrated interactions. The main interest in this line of research is to elucidate the nature of the phase transitions present in these systems.

**Professor:**

Leandro Gutierrez Rizzi

#### Interface aggregation and growth phenomena (theoretical)

Simulations, experiments and scale analyzes of the dynamics of kinetic aggregation processes are carried out here, with emphasis on the growth of self-organized nanostructures, epitaxial films, electrodeposition and propagation in porous media. In addition, a theoretical study is made of the mapping of equilibrium and far-equilibrium models in self-related interfaces.

**Professors:
**Silvio da Costa Ferreira Junior

Tiago José de Oliveira

### Magnetic Systems and Nanostructured Magnetic Materials

#### Nanofabrication and characterization of nanomagnetic systems (experimental)

We develop nanostructured systems in collaboration with national and international groups, for the characterization of their thermodynamic, magnetic and magnetoresistive behaviors. Our focus is on the application of these systems, which sometimes show frustration and, consequently, the emergence of exotic objects such as magnetic monopoles, in devices that may have characteristics of magnetic memories or that allow the performance of logical operations.

**Professor:**

Clodoaldo Irineu Levartoski de Araújo

#### Development of spintronic devices (experimental)

We use our micro and nanofabrication structure and electrical and magnetic characterization to develop and characterize spintronic devices in general. Our main interest is in the development of random-access magnetoresistive memories and transistors that can operate as highly sensitive magnetic sensors or as logical devices for integration with magnetic memories. In this line, we coordinate the Spintronics and Nanomagnetism Network and collaborate with UFV’s SisNano network.

**Professor:**

Clodoaldo Irineu Levartoski de Araújo

#### New phenomena in nanomagnetism and spintronics (experimental)

Spintronics is the area of Condensed Matter Physics that investigates phenomena related to the manipulation and transport of the electron spin angular momentum. These phenomena range from the control of a single localized spin, to the generation and manipulation of pure spin currents and their interaction with charge currents and spin waves. While controlling the properties of a single localized spin is ideal for investigating qbits in Solid State Physics, dynamic properties (spin currents and their interaction with charge currents and spin waves) are important for signal generation and manipulation using mostly electron spin. It can be said that spintronics was born in the 1980s with the seminal works that led to the discoveries of coupling between layers, giant magnetoresistance, spin valves, magnetic tunneling, etc. However, in recent years we have witnessed the discovery of a series of very intriguing new phenomena that would mean a Second revolution in this area. Among these phenomena we highlight: (i) Hall spin effect (SHE); (ii) inverse spin Hall effect (ISHE); generation of spin currents by (iii) spin pumping (SPE); (iv) generation of spin currents by thermal effects (Seebeck and Peltier spin effects); (v) interaction between spin currents and spin waves, etc.

**Professor:**

Joaquim Bonfim Santos Mendes

#### Topological excitations in materials (theoretical)

“This is not a utopia (not place), but a topia”. In the physics of modern condensed matter, there are some very stable types of excitations (objects that often resemble particles) that arise in several phenomena: topological pseudo-particles. We must emphasize the word topology, a branch of mathematics that extravagantly says that the donut would be like the cup. Topology is very common in current physics (tops comes from Greek and means place). These topological objects reside in several different systems (magnetic, liquid crystals, superconductors, etc.) mainly in low dimensions (one-dimensional and two-dimensional materials) and, due to their topological nature, are as difficult to be undone as a blind knot. The mathematical theorem of the hairy sphere is a good example to see how these topological elements can form. This stability is usually associated with a topological load. It is this aspect that makes them of great interest in the most recent research areas. Some of these structures are known as vortices, solitons, skyrmions, and have a topological load given by an integer; we can also mention the controversial Merons, which have a semi-entire topological charge.

**Professors:**

Afrânio Rodrigues Pereira

Antônio Ribeiro de Moura

Jakson Miranda Fonseca

Vagson Luiz de Carvalho Santos

Winder Alexander de Moura Melo

#### Topological States of Matter (theoretical)

Topological States of Matter are states characterized by topological properties that emerge from the system’s microscopic degrees of freedom. Examples of such states are the Whole and Fractional Quantized Hall Effect, the two-dimensional and three-dimensional Topological Insulators, topological superconductors, among countless others. This line of research involves the study of exotic properties of these materials, such as the emergence of Majorana fermions, which have an enormous potential for application in quantum computing, the presence of anyons, response functions that carry topological characteristics of the system, among others.

**Professors:**

Afrânio Rodrigues Pereira

Jakson Miranda Fonseca

Vagson Luiz de Carvalho Santos

Winder Alexander de Moura Melo

#### Magnetism and Nanomagnetism (theoretical)

“Spin is the main protagonist here”. We studied magnetic systems in low dimensions and their dynamic and thermodynamic properties, emphasizing questions about phase transition and correlation functions. Among the materials investigated by us are zero-dimension (“pontolândia”), dimension-1 (“linhalândia”), systems between 1 and 2 dimensions (“escadolândia”) and dimension-2 systems (“planolândia”) , besides, of course, the “spheroland” (three-dimensional systems). On the other hand, magnetic systems of very small sizes are also of fundamental importance for the development of new technologies. On a nanometric scale (1 centimeter divided by 10 million), many structures in condensed matter exhibit topological pseudo-particles. The nanometric magnetic structures have very interesting shapes such as disks, cylinders, racetracks, etc. Our goal is to study how these things (topology and materials of different shapes on the scale of the very small) fit together and how we could use such fittings for new technological structures. It is very common to see carousel-like movements of vortexes on magnetic nanodisks as well as skyrmion racing on magnetic nano-tracks. Controlling the movements of topological objects and even electrons in nanomagnetic systems is of fundamental importance for new technologies such as skyrmonic, spintronic, magnetronic and some other “tronics”.

**Professors:**

Afrânio Rodrigues Pereira

Antônio Ribeiro de Moura

Jakson Miranda Fonseca

Vagson Luiz de Carvalho Santos

Winder Alexander de Moura Melo

#### Frustrated magnetic systems frustrados (theoretical)

“Frustration generates exciting physics”. In this line of research, we investigated mainly spin liquids and spin ices. Such materials exhibit extraordinary properties such as disordered ground states and fractionation. Imagine a system that never organizes, even in its fundamental state at absolute zero. This is exactly what happens with spin liquids, leading to beautiful excitations such as fragmented electrons (spinons, chargons, etc.). Examples of our recent contributions involve fractionalized pseudoparticles in artificial spin ice that are called Nambu magnetic monopoles. Such monopoles have an energetic cord that connects opposite poles.

**Professors:**

Afrânio Rodrigues Pereira

Antônio Ribeiro de Moura

Jakson Miranda Fonseca

Vagson Luiz de Carvalho Santos

Winder Alexander de Moura Melo

#### New Materials (theoretical)

We are also interested and, therefore, we have investigated the properties of materials of significant importance in current physics: superconductors at high temperatures, graphene, topological insulators, etc. Some of these materials (usually two-dimensional) support massless electron-like particles and possibly Majorana fermions, which in general are only seen in condensed materials (and not in our Universe).

**Professors:**

Afrânio Rodrigues Pereira

Antônio Ribeiro de Moura

Jakson Miranda Fonseca

Vagson Luiz de Carvalho Santos

Winder Alexander de Moura Melo

#### Investigation of devices by micromagnetic simulation (theoretial)

We investigate by micromagnetic simulation, using open codes or codes developed by partners, prototypes to be produced experimentally in the future. In this line, we investigate the application of magnetic objects with topological protection in future devices to be developed experimentally. These studies have provided the proposition of several new devices to be investigated for application such as magnetoresistive tape memories, logical transistors, neuromorphic systems and nano-oscillators.

**Professors:**

Afrânio Rodrigues Pereira

Clodoaldo I. L. de Araujo

Vagson Luiz de Carvalho Santos

Winder Alexander de Moura Melo

### Mathematical Physics and Quantum Field Theory

#### Mathematical Physics and Quantum Field Theory (theoretical)

The group of Mathematical Physics and Theory of Quantized Fields develops research on the following themes: axiomatic theory of quantized fields, renormalization, problems in quantum gravity, analysis of singularities and applications, theory of generalized functions, entanglement and decompression theory in diving.

**Professors:**

Daniel Heber Theorodo Franco

Oswaldo Monteiro Del Cima

#### Quantum Field Theory Applied to Condensed Matter Systems (theoretical)

Our main objective in this line of research is to study current problems in elementary particle physics and to a lesser extent to look for connections between phenomena in this area and condensed matter physics.

**Professors:**

Afrânio Rodrigues Pereira

Antônio Ribeiro de Moura

Jakson Miranda Fonseca

Winder Alexander de Moura Melo