Seminarium Fizyki Ciała Stałego
sala 0.06, ul. Pasteura 5
2020-01-24 (10:15) 
dr Timo Hyart (Mag-TOP Instytut Fizyki Polskiej Akademii Nauk, Warszawa)
Correlated states in flat-band systems
The quenched kinetic energy in the flat-band systems increases the importance of interactions and leads to superconductivity and other correlated states. I will discuss examples of symmetry-broken states in flat-band systems starting from the best understood quantum Hall ferromagnets and exciton condensates [1] and continuing with more complicated quantum Hall systems [2] and moiré superlattices [3] which are characterized by competition between different order parameters [4]. I will emphasize that in contrast to the systems where the Fermi energy is the largest energy scale, the properties of the flat-band systems are determined by the whole band, including effects originating from the quantum metric of the Bloch wavefunctions [3,5]. Finally, I will discuss the topological properties of the flat bands appearing at the surface atomic steps in the SnTe material class [6].
References
[1] T. Hyart, B. Rosenow, Phys. Rev. B 83, 155315 (2011); D. I. Pikulin, P. G. Silvestrov, T. Hyart, Nature Communications 7, 10462 (2016).
[2] Y. Li et al., arXiv:1905.06866.
[3] T. T. Heikkilä, T. Hyart, Europhys. News 50, 24 (2019).
[4] R. Ojajärvi et al., Phys. Rev. B 98, 054515 (2018).
[5] X. Hu, T. Hyart, D. I. Pikulin, E. Rossi, Phys. Rev. Lett. 123, 237002 (2019).
[6] W. Brzezicki, M. Wysokinski, T. Hyart, Phys. Rev. B 100, 121107(R) (2019).
References
[1] T. Hyart, B. Rosenow, Phys. Rev. B 83, 155315 (2011); D. I. Pikulin, P. G. Silvestrov, T. Hyart, Nature Communications 7, 10462 (2016).
[2] Y. Li et al., arXiv:1905.06866.
[3] T. T. Heikkilä, T. Hyart, Europhys. News 50, 24 (2019).
[4] R. Ojajärvi et al., Phys. Rev. B 98, 054515 (2018).
[5] X. Hu, T. Hyart, D. I. Pikulin, E. Rossi, Phys. Rev. Lett. 123, 237002 (2019).
[6] W. Brzezicki, M. Wysokinski, T. Hyart, Phys. Rev. B 100, 121107(R) (2019).