1. Fractionalized Altermagnets: from neighboring and altermagnetic spin-liquids to fractionalized spin-orbit coupling, arXiv:2410.10949, 2024.
    With Subrata Mandal and Mathias S. Scheurer.

Published

  1. Machine learning the microscopic form of nematic order in twisted double-bilayer graphene. Nat Commun 14, 5012, 2023.
    With Stefan Obernauer, Simon Turkel, Abhay N. Pasupathy and Mathias S. Scheurer.

    • Data and source code can found in this GitHub repository.
    • See this post on phys.org/dialog for an overview to a general audience.

  2. Noncoplanar magnetic orders and gapless chiral spin liquid on the kagome lattice with staggered scalar spin chirality. SciPost Physics, v. 13, p. 050, 2022.
    With Fabrizio Oliviero, Eric C. Andrade and Rodrigo G. Pereira.

    • The gif of the continuous phase transition between cuboc-2 and cuboc-1 phases seen from the perspective of the spins in the magnetic unit cell can be seen in this link.

Book Chapters

  1. The Schrödinger Equation Written in the Second Quantization Formalism: Derivation from First Principles. In: Valentino A. Simpao; Hunter C. Little. (Org.). Understanding the Schrödinger Equation: Some [Non]Linear Perspectives. 1ed. New York: Nova Science Publishers, Inc., 2020, v. 2, p. 19-36.
    L.S.F. Olavo ; S. S. João Augusto ; FERREIRA, M.

Presentations

  1. Machine Learning the Microscopic Form of Nematic Order in twisted double-bilayer graphene, Journal Club for Quantum Physics and Machine Learning - ultracold.org, June 27, 2023 (Slides).
  2. Noncoplanar magnetism and gapless chiral spin liquid on the kagome lattice, Solid State Seminar - Universität Innsbruck, May 11, 2022 (Slides).

Unpublished Material

  • Master Dissertation (English only):

Investigating spin liquids via projected wavefunctions

J.A.S. Silva. Supervisor: Eric C. Andrade Universidade de São Paulo.
Spin liquids are exquisite states of matter which host fractionalized excitations of spin and show no long-range magnetic order even at zero temperature due to quantum fluctuations. They have been extensively studied using fractionalized representations of the spin degrees of freedom in the so-called parton construction in conjunction with the Gutzwiller projection. Using Mean Field Theories (MFT), this constraint can be imposed on average, and numerical techniques, such as the Variational Monte Carlo (VMC) are required to impose the condition exactly at each site. In this framework, the VMC is a powerful tool to indicate which MFT ansatz is favored energetically to represent the spin liquid state based on the variational principle and the specific spin fractionalized representation. We employed this approach to investigate a putative chiral spin liquid state in the Kagome lattice using the Abrikosov representation which can host spinons: neutral spin-1/2 fermionic quasiparticles. This work was performed in the J1 − Jd − Jχ Kagome Lattice model, and it was inspired by experimental results from the material α − Cu3Zn (OH)6 Cl2 (kapellasite) - a polymorphous structure of ZnCu3(OH)6Cl2 (herbertsmithite) - with no long-range order down to T = 20mK. Our VMC results favor a gapless chiral spin liquid with staggered flux ±π/2 over the triangles and 0 flux on the hexagons in the region with Jd/ |Jχ| > 0 for small |J1| < 0.1. We also investigated the stability of this spin-liquid state to ordered phases known to occur in the model. In addition, new non-coplanar ordered phases were encountered via the gradient descent method in the limit of S » 1 which may be relevant for ordered Kagome materials. By representing the influence of the ordered phases via a fictitious Zeeman field in a spin density wave (SDW) ansatz for the VMC, we have found consistent results with our classical phase diagram, establishing a more realistic region for the spin liquid domain. View PDF here.

  • Undergraduate Dissertation (Portuguese only):

Decay of accelerated fermions, Unruh Effect and applications in the semi-classical regime

J.A.S. Silva. Supervisor: C. A. S. Maia. Universidade de Brasília.
In an introduction to quantum field theory, brief notions in curved spaces and to the phenomenology of elementary particles, a revision work was developed focusing on the comprehension of the Unruh Effect in its necessity for the consistency of quantum field theory itself when considering the decay of uniformly accelerated fermions, both in an inertial reference frame and in the Rindler wedge frame. Considering particles through the formalism of semi-classical currents, another topic of study was the influence of gravitational fields in cooling mechanisms of neutron stars and the possibility of detecting particles that do not obey the famous dispersion relation in Earth’s vicinity. View PDF here.

Side Projects

  1. Three-body problem with relativistic corrections (McGill Physics Hackathon 2021).

Teaching (Assistant)

  1. (Winter Semester 2024/2025) "Fortgeschrittene Quantentheorie", lectured by Prof. Mathias Scheurer at the University of Stuttgart.
  2. (Summer Semester 2024) "Quantum Field Theory", lectured by Prof. Mathias Scheurer at the University of Stuttgart.
  3. (Winter Semester 2023/2024) "Advanced Quantum Theory", lectured by Prof. Mathias Scheurer at the University of Stuttgart.
  4. (1st semester of 2021) "Introduction to Computational Physics", lectured by Prof. Francisco Castilho Alcaraz at the University of São Paulo, São Carlos.
  5. (2nd semester of 2018) "Methods of Experimental Physics", lectured by Prof. Alexandra Mocellin at the University of Brasília.
  6. (1st semester of 2018) "Laboratory of Oscillations, Waves and Fluids", lectured by Prof. Alexandra Mocellin at the University of Brasília.
  7. (2nd semester of 2017) "Waves, Optics and Thermodynamics", lectured by Prof. Clovis Achy Soares Maia at the University of Brasília.
  8. (2nd semester of 2017) "Computational Methods A", lectured by Prof. Luiz Antonio Ribeiro Junior at the University of Brasília.
  9. (1st semester of 2017) "Laboratory of Mechanics", lectured by Prof. Júnio Marcio Rosa Cruz at the University of Brasília.
  10. (1st semester of 2016) "Calculus 1", lectured by different Professors, organized by Prof. Guy Gebrot at the University of Brasília.