Most of 2D superconductors are of type II, i.e., they are penetrated by quantized vortices when exposed to out-of-plane magnetic fields. In a presence of a supercurrent, a Lorentz-like force acts on the vortices, leading to drift and dissipation. The current-induced vortex motion is impeded by pinning at defects. Usually, the pinning strength decreases upon any type of pair-breaking interaction perturbs a system.

In the talk I will discuss surprising experimental evidences showing an unexpected enhancement of pinning in synthetic Rashba 2D superconductors when applying an in-plane magnetic field. When rotating the in-plane component of the field with respect to the driving current, the vortex inductance turns out to be highly anisotropic. We explain this phenomenon as a direct manifestation of Lifshitz invariant that is allowed in the Ginzburg-Landau free energy when space-inversion and time-reversal symmetries are broken. As demonstrated in our experiment [1], elliptic squeezing of vortices---an inherent property of the non-centrosymmetric superconducting condensate---provides an access to fundamentally new property of Rashba superconductors, and offers an entirely novel approach to vortex manipulation.

Another interesting feature of the non-centrosymmetric superconductors in the applied magnetic field is the supercurrent diode effect---the critical current in one direction exceeds its counterpart in the opposite one---what stems from the Cooper pairs with finite centre of mass momentum. In the pioneering experiment [2] we demonstrated the emergence of the supercurrent diode effect in the Josephson junctions based on synthetic Rashba superconductors made of Al-InAs quantum wells. In the talk, I will discuss novel experimental method---measurements of the Josephson inductance---and the semiquantitative microscopic model capturing all the essential features as observed in experiment.  

[1]        L. Fuchs, D. Kochan, C. Baumgartner, S. Reinhardt, S. Gronin, G. Gardner, T. Lindemann,

M. Manfra, C. Strunk, N. Paradiso; Physical Review X 12 (4), 041020 (2022).

[2]       C. Baumgartner, L. Fuchs, A. Costa, S. Reinhardt, S. Gronin, G. Gardner, T. Lindemann,

M. Manfra, P. Faria Junior, D. Kochan, J. Fabian, N. Paradiso, C. Strunk; Nature Nanotechnology 17 (1), 39 (2022).

The interplay of the spin and the orbital angular momenta of electrons in semiconductors governs the observed Zeeman splitting, often described by the effective g-factors. In the realm of 2D materials, transition metal dichalcogenides (TMDCs) are ideal candidates to explore the manifestation of coupled spin and orbital degrees of freedom under external and synthetic magnetic fields. In this talk, I will discuss two types of valley splitting signatures in TMDC-based van der Waals heterostructures: (i) effective g-factors in the presence of an external magnetic field, and (ii) nonzero valley Zeeman due to proximity exchange effects. I will cover the basic physics behind the effective g-factors, emphasizing the recent rst-principles developments that nicely reproduce the experiments in pristine[1] and strained[2] monolayer TMDCs. Employing this formalism to TMDC-based van der Waals heterostructures, particularly MoSe2/WSe2[1,3] systems, I will show that the spinvalley physics and g-factors encode valuable information about the stacking conguration and interlayer coupling. For the proximity exchange effects, I will focus on (Mo,W)Se2 on the ultrathin vdW ferromagnet CrI3[4], and (Mo,W)S2/hBN on conventional Co and Ni ferromagnets[5]. Systematically combining ab initio investigations, phenomenological modeling of the band structure and subsequent excitonic calculations, we reveal important microscopic features and signatures of the proximity exchange: despite being short ranged, these effects can be strongly tailored by external electric fields and the twist angle between the layers.

[1] Wozniak, Faria Junior et al., PRB (Editors' Suggestion) 101, 235408 (2020).
[2] Faria Junior et al., New J. Phys. 24, 083004 (2022). Blundo, Faria Junior et al., Phys.
Rev. Lett. 129, 067402 (2022). Covre, Faria Junior et al., Nanoscale 14, 5758 (2022).
[3] Faria Junior, Fabian, Nanomaterials 13, 1187 (2023).
[4] Zollner, Faria Junior, Fabian, PRB (Editors' Suggestion) 100, 085128 (2019); PRB
107, 035112 (2023).
[5] Zollner, Faria Junior, Fabian, PRB 101, 085112 (2020).

Since the discovery of Shor’s algorithm [1], which demonstrated the potential for quantum computers to break RSA encryption, quantum computing has emerged as a promising technology with the potential to solve complex problems in life sciences, clean energy, and pharmaceuticals while also revolutionizing artificial intelligence. In this talk, I will start with a brief introduction to key concepts and principles of quantum computing. Following, I will present a few examples of how quantum computers can be used to design proteins and speed up quantum machine learning tasks. To finalize, we will look at the prospect of implementing these quantum algorithms on both current and future quantum computers.
[1] P. W. Shor, "Algorithms for quantum computation: discrete logarithms and factoring". Proceedings 35th Annual Symposium on Foundations of Computer Science. IEEE Comput. Soc. Press: 124–134, (1994).
[2] M. Khatami, U. C. Mendes, N. Wiebe, P. M. Kim, "Gate-based quantum computing for protein design", PLoS Comput Biol 19(4): e1011033, (2023).

Sum of powers of principal minors (SPPM) of matrices appears in the calculation of many quantities in physics and applied mathematics. We show that the calculation of the Renyi entropy of fermionic systems, partition function of the Hubbard model and certain problems in machine learning are related to the SPPM problem. Although there is a simple formula to calculate the sum of principal minors of arbitrary matrices, it has been already shown that calculation of other powers is a hard problem (probably no polynomial time algorithm exists).
In this talk I will first discuss how the Renyi (Shannon) entropy in quantum chains detects different phases and determines the universality classes. Then I will show how calculating this quantity boils down to a SPPM problem in certain quantum systems such as Ising chain and free fermions. Finally in the main part of the talk I will write a Grassmann representation for a generic matrix SPPM problem. This field theory-like representation shows interesting symmetries such as U^n(1),  symmetric group,  axial U(1), chiral and particle-hole symmetry. Using this representation one can make a mean-field approximation and find an excellent estimate for the Renyi entropy which can detect the phase transition. We show that some of the mentioned symmetries are broken in, for example, the ferromagnetic phase of the Ising chain.

Advances in parallel computation and algorithm implementation are leading to accurate quantum mechanical descriptions of materials systems with hundreds of atoms and thousands of electrons.  Electronic structure methods based on the density functional theory with periodic boundary conditions become the workhorse in the simulations of defects in semiconductors, interfaces, and surfaces, and noststructures.  Developments in hybrid functionals have enabled accurate description of defect levels in semiconductors and insulators, defect-related absorption and emission energies, surface and interface electronic structures.  In this presentation, it will be discussed how these advanced computational methods are employed in the discovery of novel quantum materials and their exotic properties and help guide experimental efforts in the materials characterization. Specific topics to be covered include emerging topological phases in rare-earth pnictides, embedded nanoparticles in semiconductors, defects in 2D materials, and novel interface phenomena that are promising for the next generation of electronics and spintronics.

Trilhei toda a minha carreira profissional dentro de instituições de pesquisa e empresas privadas no contexto da ciência, educação e inovação, atuando como coordenadora e gerente e respirando o universo e as demandas da área de P&D fora do mundo acadêmico. Motivada pelo propósito de ampliar as oportunidades no mercado de trabalho para profissionais com mestrado, doutorado e pós-doutorado e compilando toda a bagagem adquirida nos últimos 10 anos, fundei a Pesquisadora de Impacto. Hoje, como empresária e estrategista de carreiras, foco em profissionais altamente qualificadas, para ajudar a usar toda a sua experiência acadêmica a seu favor e conquistar um emprego que as valorize em empresas e instituições privadas. De fevereiro de 2020 até hoje, já são centenas de profissionais transformadas, que ocupam as posições que sempre desejaram, sendo muito bem remuneradas e valorizadas.

Implementation of quantum information using single photons, using heralded or entangled source, have versatility to be manipulated on free space, fiber optics or photonic chips. Our project proposes the uses of photonic chips to miniaturize experimental implementations using quantum optics. The chip design can be done using a similar design of free space experimental setup or can be used designs only possible in wave-guide. The photonic chip is based on silicon nitride wave-guide, allowing the generation and manipulation of correlated photons in the visible and infrared light. This band of the electromagnetic spectrum allows the integration of different quantum computation platforms, such as: ion traps and alkaline atoms. Moreover, using semiconductor material, it is possible to make integrated single photon detectors. This project is our first step for all in one device quantum computation based on photon chips.

A prova de múltipla escolha é um método de avaliação que tem como principal vantagem a rapidez na correção e a redução da carga de trabalho do docente. No entanto, esta rapidez de correção implica em uma série de desvantagens, sendo as mais óbvias a cola facilitada e chute puro e simples. Por esta razão a utilização mais ampla de provas de múltipla escolha, especialmente no ensino universitário de ciências exatas, encontra muitos entraves. Além da facilidade fraude ou o risco de aprovar estudantes inaptos, ela sofre o estigma de ser um tipo de avaliação pouco exigente e por isso indesejável para o ensino superior. Neste seminário apresento Nenhuma Das Anteriores (NDA), um sistema de provas de múltipla escolha que desenvolvi nos últimos 12 anos no Departamento de Física da UFMG. Vou mostrar como o sistema opera, como é seu uso prático, como o sistema contorna os problemas de fraude e chute eficientemente, e como o sistema permite uma avaliação sem qualquer queda de qualidade. O uso do NDA se dá muito além de provas escritas, utilizamos o sistema amplamente para listas de exercícios e mais recentemente adaptamos seu uso ao Moodle, o que fez com que o NDA tenha se tornado uma ferramenta de ensino indispensável para o dia a dia. Por fim, vou dar uma ideia de como se implementa questões novas, como são geradas as provas, como é feita a apuração dos resultados e quais os bancos de questões que já existem.

The Trans-Neptunian Object (50000) Quaoar, classified as a cubewano, is a dwarf planet candidate with a diameter of 1,110 km, a semi-major axis of 43.7 au, and an orbital eccentricity of 0.04. Its satellite Weywot orbits at 13,300 km from the primary object, and its diameter is about 90 km, derived from its flux, assuming the same albedo as Quaoar. It allows the determination of Quaoar's mass. Over the years, several campaigns were conducted within the ERC Lucky Star project to observe stellar occultations by Quaoar and Weywot. Besides measuring Quaoar's and Weywot's sizes and shapes, those campaigns aimed at searching for material around this TNO. The events analyzed in this work were observed between 2018 and 2021, and in these high-quality occultation light curves, besides the main body occultation, secondary events were also observed, and they could be explained as a dense ring surrounding Quaoar at about 4,100 km (7.4 Quaoar radii).  One important detail is that this region is well outside the Roche limit of the central body of 1,780 km (3.2 Quaoar radii), assuming that the bulk density of particles would be around 400 kg m-3 (typical of Saturnian small satellites). This discovery will be discussed in detail during the presentation.

The advent of nanomaterials has brought several challenges on the materials' characterization framework. These challenges open for opportunities on the development of instruments capable to overcome today's technological limitations. In optical spectroscopy, diffraction mimics the capacity of conventional optical setups to extract spectral information at the nanoscale. In this seminar, I will present recent advances on the development of a near-field Raman spectroscopy system, taking place in LabNS, the Nanospectroscopy Lab of the Department of Physics, UFMG. The instrument allows for the investigation of local properties in individual nano-objects, and the information extracted from this local analysis is useful to understand statistical results extracted from measurements performed in the micro and macro scales. Supporting the instrument's technology, we have developed a new scattering-type near-field probe formed by a micro-pyramidal body whose length L is scalable to fine-tune localized surface plasmon resonance (LSPR) modes. These so-called plasmon-tunable tip pyramids (PTTPs) act as monopole antennas, as revealed by electron energy loss spectroscopy (EELS). The monopole character of the PTTP is a consequence of its geometry: the nanopiramidal part is electrically grounded on a flat metallic plateau that acts like a mirror providing the monopole's image that closes the dipole system. The talk ends with a discussion on the coherence properties of scattered fields in the proximity of the source (a material system illuminated by strongly focused by optical fields). I will demonstrate that the spatial extent of near-field correlations relies on local properties of the source which are inaccessible in the far field zone.