Ferroelectric α -In 2 Se 3 under pressure: reversible and irreversible phase transitions

Ferroelectrics are important in many technological applications, from sensors and actuators to memory and fast-switching devices. The key to their versatility lies in the coupling between their electrical and mechanical properties, which can be controlled reversibly under different external conditions. Here, we report the effects of hydrostatic pressure on structural and ferroelectric phase transitions in the van der Waals material indium selenide α -In 2 Se 3 , as probed by Raman spectroscopy and imaging in a high-pressure diamond anvil cell. We demonstrate that 2H- α -In 2 Se 3 has a stronger ferroelectric phase stability than that reported in other polytype phases of polycrystalline In 2 Se 3 . Furthermore, we show that disorder is a key factor in the reversibility of the phase transition from ferroelectric 2H- α -In 2 Se 3 to paraelectric β -In 2 Se 3 .