Condensed Matter Theory Seminar | December 21, 14:00
Engineering flat electronic bands from first mathematical principles
Engineering flat electronic bands from first mathematical principles Alexander Kruchkov Institute of Physics, EPFL, Lausanne, Switzerland Department of Physics, Harvard University, USA Branco Weiss Society in Science, ETH Zurich, Switzerland The concept of flat electronic bands is a change of paradigm in condensed matter physics. In this talk, I will address the origin of band flatness and its connection to the quantum geometry of electronic states.1 My work focuses on engineering the flat topological bands from the first mathematical principles, namely the Riemannian metrics and quantum geometry, with consequent holomorphicity and meromorphicity of the flat band states,1,2,3 enforced with accurate atomistic compu tations, DFT and tight binding with lattice relaxation effects.4,5 It provides deep insights on the origin of band flatness, which should be looked for in the real space (rather than in momentum space as conventionally it had been). In the complicated and messy domain of band structure computations, the developed approach provides an aesthetical tool for engineering flat electronic bands in realistic materials4 with consequent experimental confirmation.6,7 Time permitting, I will address the novel formalism of flatband quantum transport built on the concepts of quantum geometry.8 References: [1] A. Kruchkov, Origin of band flatness and constraints of higher Chern numbers, arXiv 2105.14672 (2021). [2.] G. Tarnopolsky, A. J. Kruchkov, A. Vishwanath, Origin of magic angles in twisted bilayer graphene, Physical Review Letters 122, 106405 (2019). [3.] E. Khalaf, A. J. Kruchkov, G. Tarnopolsky, A. Vishwanath, Magic angle hierarchy in twisted graphene multilayers, Physical Review B 100, 085109 (2019). [4.] S. Carr, C. Li, Z. Zhu, E. Kaxiras, S. Sachdev, A.J. Kruchkov, Ultraheavy and ultrarelativistic Dirac quasiparticles in sandwiched graphenes, Nano Letters (2020). [5.] F. Haddadi, Q. Wu, A. J. Kruchkov, O.V. Yazyev, Moiré flat bands in twisted double bilayer graphene, Nano Letters (2020). [6.] J.M. Park, Y. Cao, K. Watanabe, T. Taniguchi, P. JarilloHerrero, Tunable strongly coupled superconductivity in magicangle twisted trilayer graphene, Nature volume 590, (2021). [7.] Z. Hao, A. M. Zimmerman, P. Ledwith, E Khalaf, D. Najafabadi, K. Watanabe, T. Taniguchi, A. Vishwanath, P. Kim, Electric field–tunable superconductivity in alternatingtwist magicangle trilayer graphene, Science 371, 6534 (2021). [8.] A. Kruchkov, Quantum transport in dispersionless electronic bands, in preparation (2021).
Alex Kruchkov, EPFL / Harvard
zoom / https://uni-koeln.zoom.us/j/6555080253?pwd=MzVmM0xiZ2FRYmU2M05GUko0aVc4UT09
Contact: Alex Altland