Chiral phases of matter, characterized by a definite handedness, abound in
nature, ranging from the crystal structure of quartz to spiraling spin states
in helical magnets. In 1T-TiSe2​ a source of chirality has been proposed
that stands apart from these classical examples as it arises from combined
electronic charge and quantum orbital fluctuations. This may allow its
chirality to be accessed and manipulated without imposing either structural or
magnetic handedness. However, direct bulk evidence that broken inversion
symmetry and chirality are intrinsic to TiSe2​ remains elusive. Here,
employing resonant elastic scattering of x-rays, we reveal the presence of
giant circular dichroism up to ∼ 40% at forbidden Bragg peaks that
emerge at the charge and orbital ordering transition. The dichroism varies
dramatically with incident energy and azimuthal angle. Comparison to calculated
scattering intensities unambiguously traces its origin to bulk chiral
electronic order in TiSe2​ and establishes resonant elastic x-ray
scattering as a sensitive probe to electronic chirality.Comment: 6 pages, 4 figure