The ferroelectric semiconductor α-SnTe has been regarded as a
topological crystalline insulator and the dispersion of its surface states has
been intensively measured with angle-resolved photoemission spectroscopy
(ARPES) over the last decade. However, much less attention has been given to
the impact of the ferroelectric transition on its electronic structure, and in
particular on its bulk states. Here, we investigate the low-energy electronic
structure of α-SnTe with ARPES and follow the evolution of the
bulk-state Rashba splitting as a function of temperature, across its
ferroelectric critical temperature of about Tc∼110 K. Unexpectedly, we
observe a persistent band splitting up to room temperature, which is consistent
with an order-disorder contribution to the phase transition that requires the
presence of fluctuating local dipoles above Tc. We conclude that no
topological surface state can occur at the (111) surface of SnTe, at odds with
recent literature.Comment: 26 pages, 8 figure