| Description |
Abstract: There are plenty of lattices in one, two, and three dimensions which support a completely dispersionless (flat) one-particle energy band. If the flat band happens to be the lowest-energy one, it is possible to construct and completely characterize a certain manifold of many-particle ground states even in the presence of strong interactions. These states determine the low-temperature properties of strongly correlated systems in a specific range of external parameters [1]. In this talk I discuss the effect of slight dispersion of a previously strictly flat band. I focus on the high-field low-temperature properties of some quantum Heisenberg antiferromagnets [2] and on the kinetic-energy-driven ground-state ferromagnetism in the standard Hubbard model at low electron densities [3]. I also discuss why these findings are useful in searching for experimental manifestation of flat-band effects in strongly correlated systems. [1] O. Derzhko, J. Richter, and M. Maksymenko, Int. J. Mod. Phys. B 29, 1530007 (2015). [2] O. Derzhko, J. Richter, O. Krupnitska, and T. Krokhmalskii, Phys. Rev. B 88, 094426 (2013); Low Temp. Phys. 40, 513 (2014); J. Richter, O. Krupnitska, T. Krokhmalskii, and O. Derzhko, J. Magn. Magn. Mater. 379, 39 (2015). [3] O. Derzhko and J. Richter, Phys. Rev. B 90, 045152 (2014); P. Müller, J. Richter, and O. Derzhko, Phys. Rev. B 93, 144418 (2016). |
Condensed Matter Seminar: 'Strongly Correlated Systems with Nearly Flat Bands'
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