Brief interviews with scientists: Bernhard Keimer (Max Planck Institute for Solid State Research, Germany).


Prof. Bernhard Keimer
Prof. Bernhard Keimer

Superconductivity and giant magnetoresistance are examples of phenomena that can occur in some materials or systems driven by the so-called electronic correlation, in which the behavior of an electron is strongly influenced by the behavior of other electrons of the same system.

At one of the Max Plank Institutes, located in Stuttgart, Germany, a group of researchers led by Professor Bernhard Keimer works hard to understand and control the behavior of correlated electrons. For this, the team produces heterostructures (structures composed of several materials with differentiated characteristics) of metallic oxides, and characterizes them using a series of experimental techniques, mainly of spectroscopy.

Professor Keimer will be at the XVII B-MRS Meeting in September talking about this research program in the lecture “Spectroscopy of collective excitations in oxide heterostructures”. In his plenary talk, Keimer will present methods and results, including some possibilities of controlling correlated-electrons phenomena.

Bernhard Keimer has been director of the Max Planck Institute for Solid State Research as well as honorary professor at the University of Stuttgart since 1998. From 1992 to 1998, he was Professor of Physics at Princeton University. He graduated in Physics from the Technical University of Munich in 1985 and, in 1991, obtained his PhD in Physics from the Massachusetts Institute of Technology (MIT), where he remained for one year as a postdoc. According to Google Scholar, Keimer has an H index of 86 and his scientific production has more than 24,500 citations.

See our mini interview with this German scientist.

B-MRS Newsletter: – One of the goals of the research you perform with your team at the Max Plank Institute is to control the behavior of strongly correlated electrons, right? In your opinion, what could be the most promising applications emerging from this control? Comment shortly, please.

Bernhard Keimer: – Quantum correlations between electrons generate a large variety of electronic ordering phenomena with vastly different macroscopic properties. Understanding and controlling the collective behavior of electrons in “quantum materials” is a grand intellectual challenge for fundamental research. In the long term, research on quantum materials might enable the design of a new generation of devices based on electrons flow with minimal – or even zero – dissipation.

B-MRS Newsletter: – We want to know more about your work. Please choose a paper of your own (your favorite one) related to the subject of the plenary lecture and briefly describe it, as well as share the reference.

Bernhard Keimer: – As a general introduction to the physics of quantum materials, I recommend a recent review article (B. Keimer & J.E. Moore, Nature Physics 13, 1045 (2017)) A particularly fascinating topic is high-temperature superconductivity. My group uses heterostructures and superlattices to investigate novel collective phenomena emerging at the interface between high-temperature superconductors and other quantum materials. As an example, the figure below shows a kaleidoscope of quantum phases in a 50 nm thin layer of a copper oxide superconductor sandwiched between two layers of an oxide ferromagnet (A. Frano et al., Nature Materials 15, 831 (2016)). My group is developing spectroscopic methods that allow visualization of these phases in a depth-resolved manner.

This schematic figure above shows electronic ordering phenomena in a layer of the high-temperature superconductor YBa2Cu3O7 (YBCO) between two ferromagnetic manganese-oxide layers as a function of temperature (T) and distance across the layer. FM = ferromagnetism, SC = superconductivity, AFI = antiferromagnetic insulator, SDW = spin density wave, CDW = charge density wave. The graph below shows the density of mobile charge carriers, p, as a function of distance. (A. Frano et al., Nature Materials 15, 831 (2016)).
This schematic figure above shows electronic ordering phenomena in a layer of the high-temperature superconductor YBa2Cu3O7 (YBCO) between two ferromagnetic manganese-oxide layers as a function of temperature (T) and distance across the layer. FM = ferromagnetism, SC = superconductivity, AFI = antiferromagnetic insulator, SDW = spin density wave, CDW = charge density wave. The graph below shows the density of mobile charge carriers, p, as a function of distance. (A. Frano et al., Nature Materials 15, 831 (2016)).

 

For more information on this speaker and the plenary talk he will deliver at the XVII B-MRS Meeting, click on the speaker’s photo and the title of the speech here https://www.sbpmat.org.br/17encontro/home/

Interviews with plenary speakers of the XIV SBPMat Meeting: Ulrike Diebold.


Metal oxides display a wide range of properties. Accordingly, they become useful in numerous applications, such as gas sensing, catalysis, protection against corrosion, pigmentation, energy conversion, to name a few. An important detail: in order to comprehend and use these materials, the study of their surface is crucial.

Prof. Ulrike Diebold.

Metal oxides surfaces will be the theme of a plenary talk of the XIV SBPMat Meeting. The speech will be given by Ulrike Diebold, a scientist among the leading experts on the subject in the world. Diebold is engaged in surface science since the time of her doctoral degree, defended in 1990 at the Vienna University of Technology (TU Wien), in Austria. A few years later, during her postdoctoral studies in a surface group at Rutgers University, in New Jersey (USA), she started her researches on titanium dioxide. In 1993, she became a Professor of Tulane University, in the city of New Orleans (USA) and she founded and coordinated a group on surface science.  When the group labs were hit by hurricane Katrina in 2005, Diebold was welcomed by several institutions and settled, jointly with some members of the Tulane group, in Rutgers. Finally, she went back to the place where her scientific career had started, TU Wien, as a Professor and coordinator of the surface physics group. With her research groups, Diebold continues to advance in her basic and applied science studies on metal oxides, based, among other techniques, on scanning tunneling microscopy (STM), through which the scientist can investigate these materials at atomic scale.

Ulrike Diebold is the author of more than 180 peer-reviewed articles, which have over 12,000 citations. Her h-index, according to Web of Science, is 52. The scientist has already delivered more than 250 invited talks. Throughout her career, she has received numerous awards and distinctions from several entities such as the Alexander von Humboldt Foundation, American Chemical Society, Austrian Academy of Sciences, Austrian Ministry for Science, Catalysis Society of South Africa, Czech Republic Academy of Sciences, European Academy of Sciences, German National Academy of Sciences Leopoldina, National Science Foundation, among others. She is an associate editor for the Materials Physics Division of the journal Physical Review Letters.

What follows is a mini-interview with this plenary speaker of the XIV SBPMat Meeting

STM image of single Au atoms on an Fe3O4 surface.  This system acts as a model catalyst to study simple reactions with atomic-scale detail. The related experiment is described in: Novotný, Z. et al. Ordered Array of Single Adatoms with Remarkable Thermal Stability: Au/Fe_{3}O_{4}(001). Phys Rev Lett 108, (2012).

SBPMat newsletter: – In your opinion, what are your most significant contributions in the field of metal oxides surfaces? Please explain them, very briefly, and share references from the resulting articles or books, or comment if these studies have produced patents or products.

Ulrike Diebold: – The field started with the book “The Surface Science of Metal Oxides” by Vic Henrich and P.A. Cox, which was published in 1993 (Cambridge University Press).  The book has motivated many people to develop an interest in metal oxide surfaces, and research has progressed tremendously since that time.  Some is still valid to this day, e.g., the importance of defects for understanding the properties of oxide surfaces, and how critical it is to master surface preparation.  Meaningful investigations can only be conducted on ‘well-characterized’ systems with a known and controlled surface structure.  About ten years later, in 2003, I wrote a review that focused only on titanium dioxide, which is a widely-used material both in applications and in fundamental research (Surface Science Reports 48 (2003) 53).  This review has received quite a bit of attention.   Another decade later a whole issue of Chemical Reviews (vol. 113, 2013) was focused on metal oxide surfaces, which pretty much summarizes the state-of-the art in metal oxide surface research.

SBPMat newsletter: – Comment on the possibilities offered by tunneling microscopy to the study of surfaces, especially metal oxides surfaces.

Ulrike Diebold: – Scanning Tunneling Microscopy, which was invented by Heinrich Rohrer and Gerd Binnig in the early 1980s, has revolutionized our understanding of the nanoworld.  One can use this technique for imaging the geometric and electronic structure of a surface at the local scale, atom-by-atom.  This is particularly important for oxides, where it is often the irregularities in the lattice that are the most interesting entities, i.e., defects such as missing atoms, interstitials, or impurities.  Scanning Tunneling Microscopy is the ideal tool to investigate such defects at the atomic level and to literally ‘watch’ defect-mediated chemical reactions.

 STM image of defects on a TiO2 surface. The related experiment is described in Dulub, O. et al. Electron-induced oxygen desorption from the TiO2(011)-2×1 surface leads to self-organized vacancies. Science 317, 1052–1056 (2007).

SBPMat newsletter: – If you wish, leave a message or an invitation to your plenary talk to the readers who will attend the XIV SBPMat Meeting.

Ulrike Diebold: – I think it is simply exciting to observe phenomena such as defects disappearing from a surface and coming back, or single molecules dissociating or diffusing across a surface.  If you want to see beautiful pictures and movies of processes that could potentially be relevant to your own research, please come to my talk.

More

Oportunidade de bolsa de pós-doutoramento em Engenharia de Materiais vinculada ao CEPID Centro de Desenvolvimento de Materiais Funcionais.


Nesse projeto pretende-se entender profundamente os processos envolvidos na sinterização ativada de nanocristais de óxidos metálicos pela visualização direta dos fenômenos durante sua ocorrência por microscopia eletrônica de transmissão in situ, em resolução atômica. Desse estudo, pretende-se desvendar os mecanismos da sinterização ativada pela observação direta dos fenômenos, com possíveis formulações de modelos quantitativos e qualitativos do processo.

O selecionado trabalhará no laboratório coordenado pelo Prof. Edson R. Leite no Departamento de Química da Universidade Federal de São Carlos na área de Química de Materiais. A vaga está aberta a brasileiros e estrangeiros altamente qualificados. O selecionado receberá Bolsa de Pós-Doutorado da FAPESP (no valor de R$ 5.908,80 mensais) e Reserva Técnica. A Reserva Técnica de Bolsa de PD equivale a 15% do valor anual da bolsa e tem o objetivo de atender a despesas relacionadas à atividade de pesquisa.

São desejáveis as seguintes competências para o candidato:

  • Ter título de doutor (adquirido nos últimos três anos) em física, química ou engenharia de materiais, com tese na área de microscopia eletrônica e/ou sinterização de nanomateriais.
  • Sólida experiência em microscopia eletrônica de transmissão (evidenciada por publicações). Práticas anteriores em experimentos de microscopia eletrônica in situ serão consideradas na seleção.
  • Experiência em processamento e síntese de nanocristais.
  • Ter publicações científicas e domínio da língua inglesa.

Os interessados devem enviar os seguintes documentos (em PDF), até 30 de agosto de 2013, para o email do Prof. Dr. Edson R. Leite (edson.leite@pq.cnpq.br):

  • Carta de motivação.
  • Resumo da tese de doutorado.
  • Curriculum Vitae Completo.

Duas referências para contato.