Electronic structure of the gold complexesCs2Au2X6

Single crystal growth by self-flux method of the mixed valence gold halides Cs2[Au X2][Au X4] (X=Br,I)

“…The measured transport gap (550 meV for X¼I) is considerably less than the estimates of the minimum intervalence charge transfer (IVCT) excitation determined from optical reflectivity measurements ( % 806 meV for the Au I ð5d z 2 ) to Au III ð5d x 2 Ày 2 ) transition for Cs 2 Au 2 I 6 observed for electric fields oriented perpendicular to the crystallographic c-axis) determined from optical reflectivity measurements [7].…”

“…Although simple charge counting arguments might indicate a single gold valence Au II , and hence a metallic state, the materials are in fact found to be hard insulators, comprising two distinct Au sites with different formal valences Au I and Au III [1][2][3][4][5]. However, hydrostatic pressure can induce a coupled first order structural and valence transition at % 9 GPa for X¼Br and % 5:5 GPa for X¼I, spurring considerable recent interest in the associated changes in the electronic behavior [1,6,7].…”

Pressure-induced symmetry breaking in tetragonal CsAuI3

“…Evidence from early experiments indicated that pressure lead to a higher crystal symmetry through first order structural transition for the chloride, bromide and iodide at 12.5, 9 and 5.5 GPa respectively 4 5 6 . Additional experimental evidence based on Raman spectroscopy 7 and Mossbauer spectroscopy 8,9 suggests that coupled to the structural transition there is an associated mixed valence (MV) to single valence (SV) transition, although it is not clear whether these necessarily occur at exactly the same pressure and temperature 6 . In order to understand the origin of the suppression of this charge density wave state with applied pressure, it is necessary to carefully investigate the evolution of the crystal structure, which is the purpose of the current work.…”

Ultrafast pump-probe measurements of short small-polaron lifetimes in the mixed-valence perovskite Cs2Au2I6Trigo1, Chen2, Jiang3 et al. 2012Phys. Rev. B230160View full textAdd to dashboardCite

“…1 (b): the first pulse induces the electronic charge transfer (left, 550 nm). This photon energy is close to the 5d xy → 5d x 2 −y 2 transition between Au 1+ and Au 3+ [17], which "prepares" the system into a significant fraction of Au 2+ sites. The pulse duration was stretched to 600 fs to avoid generating coherent phonons by impulsive excitation [16] with the "preparation" pulse.…”