Research Seminars

Here you find the schedule and video files of our research seminars on X-ray scattering and spectroscopy of quantum materials. All seminars are in Portuguese, except when mentioned otherwise.

Next seminar:

Seminário 8: vídeo file

Palestrante: Dr. Alysson Ferreira de Moraes (Instituto de Física da USP, USP, São Paulo)

Data: 19/03/2021, sexta feira as 16:00 horas

Título: Mesostructuring layered materials

To address the high demand for new functional materials from fields such as catalysis, separation science, gas storage and sensing, material scientists are continuously investing major efforts in the development of new functional porous materials. Even so, the research community dedicated to the study of Layered Double Hydroxides (LDHs), a class of lamellar solids, has struggled to impose a 3D hierarchy in these materials. In general, LDHs only present micropores, the size of which is dictated by the size of the interlayer molecules. Examples of hierarchical LDHs with accessible mesopores are rather limited, this small club so far being composed of LDH nanocones, nanospheres and nanoscrolls. Mesostructuring LDHs has proven to be very challenging. I will show that the self-assembly of self-supported LDH nanotubes can be achieved by using a soft-templating strategy in combination with the incorporation of 8-fold coordinated lanthanide sites in the hydroxide layers. Doping trivalent rare earth elements into the LDH sheets allows the hydroxide layers to curve, enabling self-assembly of these sheets onto convex soft-template surfaces. Combining this approach with Pluronic P-123 worm-like micelles used as templates enabled the synthesis of well-defined, multi-walled, hollow, cylindrical LDH nanotubes with typical central gallery of 20 nm and a specific surface area 5-fold higher as compared to standard flake-like LDHs. This realization reveals compelling insights into potential routes to mesostructure layered materials and could inspire researchers to design new hierarchically structured lamellar solids or to even further extend the artillery of mesostructuring approaches available for designing and optimizing new functional materials from layered precursors.

Past seminars

Seminário 7: no video

Palestrante: Damaris T Maimone (Paul Scherrer Institut, Villigen PSI, Switzerland)

Data: 04 de Agosto de 2020

Título: Electron-phonon coupling in CuSb2O6

The coupling between electronic and phononic degrees of freedom gives rise to remarkable exotic phenomena in condensed matter, such as superconductivity and colossal magnetoresistance. These intertwined ground states may also have mixed lattice and electronic excitations. The well-known Jahn-Teller effect on transition metal ions is an example of orbital-lattice coupling mechanism. Since the energy scales of the electronic splitting of eg levels do not match the phononic energy scale, usually these excitations do not directly mix. In this study, we reported evidence for lowenergy orbital dynamics that strongly interact with phonons in a so-far unexplored first order type of electron-phonon interaction [1]. In addition, lattice dynamical calculations reveal that the observed anomalous phonon frequency shifts only occur for phonon modes with participation of the apical oxygen [2]. This confirms the magnetic correlations along the Cu-O-O-Cu as well as the origin of the one dimensional magnetic correlations observed in CuSb2O6.

Reference papers: [1] D. T. Maimone, e at, Phys. Rev. B 97, 174415 (2018) [2] ] D. T. Maimone, et al, Phys Rev. B 17, 104304 (2018)

Seminário 6: video file

Palestrante: Prof. Dr. Luis Henrique de Lima

Data: 23 de junho de 2020

Título: Probing the local atomic structure of surface-supported 2D materials

Reference papers: L. H. de Lima et al, 2D Materials 7, 035006 (2020), R.C.C. Ferreira et al, Chemistry of Materials 30, 7201 (2018).

Seminário 5: video file

Palestrante: Dr. Oleh Ivashko - DESY

Data: 09 de junho de 2020

Título: Competition between Charge Density Wave and Superconductivity

Reference paper: https://www.nature.com/articles/s41467-020-14536-1

Seminário 4: no video

Palestrante: Dr. Heike Pfau - Lawrence Berkeley National Laboratory

Data: 12 de maio de 2020

Título: Nematicity studied with strain-dependent ARPES

Seminário 3: video file

Palestrante: Dr. Eduardo Bittar - CBPF

Data: 05 de maio de 2020

Título: Exploring charge density waves quantum phase transition by x-ray diffraction.

Seminário 2: video file

Palestrante: Rodolfo Tartaglia, doutorando, IFGW-UNICAMP

Data: 28 de abril de 2020

Título: Estruturas e Transições Magnéticas dos compostos GdNiSi3 e TbNiSi3

Seminário 1: video file

Palestrante: Carlos Galdino, doutorando, IFGW-UNICAMP

Data: 14 de abril de 2020

Título: Couplling of eletronic excitations with the crystal lattice