2021 Fiscal Year Research-status Report
Novel Quantum States in Topological Kondo insulators
| Project/Area Number |
18K03511
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| Research Institution | Kyoto University |
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Principal Investigator |
Peters Robert 京都大学, 理学研究科, 講師 (80734293)
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| Project Period (FY) |
2018-04-01 – 2023-03-31
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| Keywords | topology / strong correlations / Kondo insulator / Weyl-Kondo semimetal / nonlinear Hall effect / heat conductivity |
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| Outline of Annual Research Achievements |
We continued our research about the interplay between strong correlations and topology in a Weyl-Kondo semimetal. The study has been motivated by recent experiments showing a giant nonlinear Hall effect in the Weyl-Kondo semimetal, Ce3Bi4Pd3. We found that due to strong correlations, the f electrons disappear from the Fermi energy at high temperatures resulting in a metallic state. At low temperatures, the f electrons emerge at the Fermi energy below the Kondo temperature, leading to the formation of Weyl points at the Fermi energy. Furthermore, we studied the nonlinear response in this system and found that the nonlinear response, especially the nonlinear Hall effect, is strongly enhanced due to strong correlation effects. Our results give a qualitative explanation of the experimental findings and have been published in Phys. Rev. B.
Furthermore, we analyzed the charge and heat conductivity in a one-dimensional Kondo insulator. Recent experiments have found that some Kondo insulators show finite heat transport although the system is charge insulating. To include even exotic excitations in our analysis, such as Excitons and Spinons, we directly calculated the current-current correlation functions using variational matrix product states. To our knowledge, this has been the first time these current-current correlation functions have been calculated for a Kondo insulator. Although our study includes every kind of possible excitation, unfortunately, we have not found finite heat conductivity at temperatures where the system is charge insulating.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
The research progressed as planned. We could publish our result about the nonlinear Hall effect in Weyl-Kondo semimetals. Furthermore, we finished our calculations about charge and heat conductivity in the one-dimensional Kondo insulator, including exotic excitations. These results are currently summarized in a research paper soon to be submitted.
Furthermore, we finished our calculations about quantum oscillations in topological Kondo insulators at very high magnetic fields, where the magnetic field destroys the gap of the insulator, i.e., a magnetic breakdown occurs.
These results are currently analyzed and will be prepared for publication soon.
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| Strategy for Future Research Activity |
In the last year of this project, we will extend our calculations about the charge and heat transport in the one-dimensional Kondoinsulator. Although we have included the possibility of exotic excitations into our previous calculation by directly calculating the current-current correlations function, we have not found any heat transport when the system is charge insulating. However, experiments have shown that heat transport is possible in some Kondo insulators. We thus plan to vary our model of a Kondo insulator by including new interaction terms and study the emergence of charge neutral excitations and their impact on the heat conductivity.
A second project, we plan to study the nonlinear response in topological Kondoinsulators. In particular, we will focus on the calculations of the second-harmonic generation and the photovoltaic effect in noncentrosymmetric systems. We will analyze the impact of topology and strong correlations on the nonlinear response in these systems.
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| Causes of Carryover |
Due to the ongoing Covid-19 pandemic, travel to international conferences was not possible.
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