Přednášející: Urko Petralanda Holguin (Department of Dielectrics, FZÚ AV ČR, v.v.i.)
Místo: Na Slovance, seminární místnost 117
Jazyk: anglicky
Pořadatelé:
Oddělení teorie kondenzovaných látek
Abstract: Despite their structural similarities, SrBi2Ta2O9 (SBT) and SrBi2Nb2O9 (SBN) undergo different sequences of phase transitions. SBT presents an intermediate phase between the high-temperature phase and the ferroelectric ground state, while in SBN it is absent. Ab initio calculations are performed, showing that the trilinear coupling between three symmetry-adapted modes is relevant to stabilize the ground state in both compounds, being it stronger in SBN than in SBT. Within the framework of the phenomenological Landau theory we show that solely tuning this parameter, the topology of the phase diagram of SBT can change enough to suppress the intermediate phase. Monte Carlo simulations on an idealized φ4 Hamiltonian confirm this view, and that for higher dimensionality of the order parameters the stability region of the intermediate phase is narrower.
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