Structural correlations in Cs_2CuCl_4 : Pressure dependence of electronic structures

• Published in: Papers in physics 2019-06, Vol.11, p.11004
• Main Authors: Enrique Jara, Jose Antonio Barreda-Argüeso, Jesus Antonio González, Rafael Valiente, Fernando Rodriguez
• Format: Article
• Language: English
• Subjects: band gap; Cs2CuCl4; electronic structure; high pressure
• ISSN: 1852-4249; 1852-4249
• DOI: 10.4279/PIP.110004

We have investigated the crystal structure of Cs_2CuCl_4 in the 0-20 GPa range as a function of pressure and how pressure affects its electronic properties by means of optical absorption spectroscopy. In particular, we focused on the electronic properties in the low-pressure Pnma phase, which are mainly related to the tetrahedral CuCl_4^{2-} units distorted by the Jahn-Teller effect. This study provides a complete characterization of the electronic structure of Cs_2CuCl_4 in the Pmna phase as a function of the cell volume and the Cu-Cl bond length, R_{Cu-Cl}. Interestingly, the opposite shift of the charge-transfer band-gap and the Cu^{2+} d-d crystal-field band shift with pressure are responsible for the strong piezochromism of Cs_2CuCl_4. We have also explored the high-pressure structure of Cs_2CuCl_4 above 4.9 GPa yielding structural transformations that are probably associated with a change of coordination around Cu^{2+}. Since the high-pressure phase appears largely amorphized, any structural information from X-ray diffraction is ruled out. We use electronic probes to get structural information of the high-pressure phase.