Dielectric and electrical properties of SbSI and SbSeI single crystals in the region of antiferroelectric phase transition

• SbSI and SbSeI show sharp changes in electrical conductivity at 410 K.
• A strong hysteresis loop is seen while heating and cooling samples.
• We report a theoretical interpretation of the experimentally observed effect.

Experimental results have shown that the capacitance (dielectric permittivity) and electrical conductivity of SbSI and SbSeI crystals along the c(z)-axis change significantly in the region of the antiferroelectric phase transition when DC voltage is applied. An electric field changes the form of B1u (A1) soft mode potential in sites of Sb atoms, which turns the antiferroelectric phase into an induced ferroelectric phase. Degenerate energy levels then split into non-degenerate levels due to electron–phonon interaction (pseudo Jahn–Teller effect), while a narrowed band gap simultaneously creates strong and abrupt changes in C(T  ) and σ(T)σ(T).