Événements
MatQ - Groupes Sénéchal et Taillefer
Date : 9 février 2023 11:00
Type : Institut Quantique
Lieu : Auditorium IQ
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Through the steps of electronic structure calculations of strongly correlated electron systems
---- presented by Benjamin Bacq-Labreuil, from the Sénéchal Group ----
The family of the strongly correlated electron systems is characterized by the fact that the kinetic energy of the electron is of the order of the Coulomb interaction. The strong competition between the two terms, leading to the breaking of the usual weak/strong coupling approximations, is at the heart of many exceptional emergent phenomena: high-temperature superconductivity, giant magnetoresistance, ferroelectricity, to name a few. A key step in understanding these different properties is to calculate the electronic structure of the materials in which they emerge, so to obtain insights on the responsible mechanisms. This is a great challenge, since the usual methods based solely on density functional theory (DFT), i.e. on the one-electron picture, cannot reliably describe the strongly correlated degrees of freedom. The latter have to be treated separately using effective models such as the famous Hubbard model, which can be solved for instance with dynamical mean-field theory (DMFT). In this talk, with a help of a simple example, I will guide you through the main steps of modern electronic structure calculations for strongly correlated electron systems, and show how the combination of DFT+DMFT can provide an astonishing agreement between theory and experiment.
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Electrons with Planckian scattering obey standard orbital motion in a magnetic field
---- presented by Amir Ataei, from the Taillefer Group ----
In various so-called strange metals, electrons undergo Planckian dissipation, a strong and anomalous scattering that grows linearly with temperature, in contrast to the quadratic temperature dependence expected from the standard theory of metals. In some cuprates and pnictides, a linear dependence of resistivity on a magnetic field has also been considered anomalous—possibly an additional facet of Planckian dissipation. Here we show that the resistivity of the cuprate strange metals Nd0.4La1.6−xSrxCuO4 and La2−xSrxCuO4 is quantitatively consistent with the standard Boltzmann theory of electron motion in a magnetic field, in all aspects—field strength, field direction, temperature and disorder level. The linear field dependence is found to be simply the consequence of scattering rate anisotropy. We conclude that Planckian dissipation is anomalous in its temperature dependence, but not in its field dependence. The scattering rate in these cuprates does not depend on field, which means that their Planckian dissipation is robust against fields up to at least 85 T.
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You can also join us on Teams.
Rejoindre la réunion Microsoft Teams / Join the Microsoft Teams meeting
Through the steps of electronic structure calculations of strongly correlated electron systems
---- presented by Benjamin Bacq-Labreuil, from the Sénéchal Group ----
The family of the strongly correlated electron systems is characterized by the fact that the kinetic energy of the electron is of the order of the Coulomb interaction. The strong competition between the two terms, leading to the breaking of the usual weak/strong coupling approximations, is at the heart of many exceptional emergent phenomena: high-temperature superconductivity, giant magnetoresistance, ferroelectricity, to name a few. A key step in understanding these different properties is to calculate the electronic structure of the materials in which they emerge, so to obtain insights on the responsible mechanisms. This is a great challenge, since the usual methods based solely on density functional theory (DFT), i.e. on the one-electron picture, cannot reliably describe the strongly correlated degrees of freedom. The latter have to be treated separately using effective models such as the famous Hubbard model, which can be solved for instance with dynamical mean-field theory (DMFT). In this talk, with a help of a simple example, I will guide you through the main steps of modern electronic structure calculations for strongly correlated electron systems, and show how the combination of DFT+DMFT can provide an astonishing agreement between theory and experiment.
----------------------------------------------
Electrons with Planckian scattering obey standard orbital motion in a magnetic field
---- presented by Amir Ataei, from the Taillefer Group ----
In various so-called strange metals, electrons undergo Planckian dissipation, a strong and anomalous scattering that grows linearly with temperature, in contrast to the quadratic temperature dependence expected from the standard theory of metals. In some cuprates and pnictides, a linear dependence of resistivity on a magnetic field has also been considered anomalous—possibly an additional facet of Planckian dissipation. Here we show that the resistivity of the cuprate strange metals Nd0.4La1.6−xSrxCuO4 and La2−xSrxCuO4 is quantitatively consistent with the standard Boltzmann theory of electron motion in a magnetic field, in all aspects—field strength, field direction, temperature and disorder level. The linear field dependence is found to be simply the consequence of scattering rate anisotropy. We conclude that Planckian dissipation is anomalous in its temperature dependence, but not in its field dependence. The scattering rate in these cuprates does not depend on field, which means that their Planckian dissipation is robust against fields up to at least 85 T.
Vous pouvez aussi vous joindre à nous par Teams.
You can also join us on Teams.
Rejoindre la réunion Microsoft Teams / Join the Microsoft Teams meeting