Understanding the Pressure Effect on the Elastic, Electronic, Vibrational, and Bonding Properties of the CeScO3 Perovskite

D.E. acknowledges the financial support given by the Spanish Ministry of Science, Innovation, and Universities (MCIU) under grant nos. PID2019-106383GB-C41 and RED2018-102612-T (MALTA Consolider-Team network) and by Generalitat Valenciana under Grant Prometeo/2018/123 (EFIMAT). R.F. and A. Lobato are grateful to financial support from Spanish MCIU under grant PGC2018-094814-B-C22. We would like to thank TGCC under the allocation 2020-A0080910433 made by GENCI, the PMMS (Pôle Messin de Modélisation et de Simulation), the Tirant supercomputer (Universitat de Valencia), and the MALTA-Consolider facilities for providing us the computational resources. S.G. and M.B. also acknowledge financial su…

High-pressure studies of topological insulators Bi2Se3, Bi2Te3, and Sb2Te3

Bi2Se3, Bi2Te3, and Sb2Te3 are narrow bandgap semiconductors with tetradymite crystal structure (R-3m) which have been extensively studied along with their alloys due to their promising operation as thermoelectric materials in the temperature range between 300 and 500¿K. Studies on these layered semiconductors have increased tremendously in the last years since they have been recently predicted and demonstrated to behave as 3D topological insulators. In particular, a number of high-pressure studies have been done in the recent years in these materials. In this work we summarize the main results of the high-pressure studies performed in this family of semiconductors to date. In particular, w…

Structural Metastability and Quantum Confinement in Zn1–xCoxO Nanoparticles

This paper investigates the electronic structure of wurtzite (W) and rock-salt (RS) Zn1-xCoxO nanoparticles (NPs) by means of optical measurements under pressure (up to 25 GPa), X-ray absorption, and transmission electron microscopy. W-NPs were chemically synthesized at ambient conditions and RS-NPs were obtained by pressure-induced transformation of W-NPs. In contrast to the abrupt phase transition in W-Zn1-xCoxO as thin film or single crystal, occurring sharply at about 9 GPa, spectroscopic signatures of tetrahedral Co(2+) are observed in NPs from ambient pressure to about 17 GPa. Above this pressure, several changes in the absorption spectrum reveal a gradual and irreversible W-to-RS pha…

High-pressure phase transitions and compressibility of wolframite-type tungstates

This paper reports an investigation on the phase diagram and compressibility of wolframite-type tungstates by means of x-ray powder diffraction and absorption in a diamond-anvil cell and ab initio calculations. The diffraction experiments show that monoclinic wolframite-type MgWO4 suffers at least two phase transitions, the first one being to a triclinic polymorph with a structure similar to that of CuWO4 and FeMoO4-II. The onset of each transition is detected at 17.1 and 31 GPa. In ZnWO4 the onset of the monoclinic-triclinic transition has been also found at 15.1 GPa. These findings are supported by density-functional theory calculations, which predict the occurrence of additional transiti…

Trapping of three-dimensional electrons and transition to two-dimensional transport in the three-dimensional topological insulator Bi2Se3under high pressure

This paper reports an experimental and theoretical investigation on the electronic structure of bismuth selenide (Bi2Se3) up to 9 GPa. The optical gap of Bi2Se3 increases from 0.17 eV at ambient pressure to 0.45 eV at 8 GPa. The quenching of the Burstein-Moss effect in degenerate samples and the shift of the free-carrier plasma frequency to lower energies reveal a quick decrease of the bulk three-dimensional (3D) electron concentration under pressure. On increasing pressure the behavior of Hall electron concentration and mobility depends on the sample thickness, consistently with a gradual transition from mainly 3D transport at ambient pressure to mainly two-dimensional (2D) transport at hi…

Photoluminescence in ZnO:Co2+ (0.01%–5%) Nanoparticles, Nanowires, Thin Films, and Single Crystals as a Function of Pressure and Temperature: Exploring Electron–Phonon Interactions

This work investigates the electronic structure and photoluminescence properties of Co2+-doped ZnO and their pressure and temperature dependences through high-resolution absorption and emission spe...

Local structure in Ga1−xInxSe alloys

Abstract In this work we study the local structure of layered G a 1 − x I n x S e alloys by means of X-ray Absorption. We complement our research with a Raman study. The available alloys have compositions close to the host binaries. The dependence of XANES (X-ray Near Edge Structure) features with synchrotron polarization clearly establishes the substitutional character of the alloying cations. Interstitial atoms, if present, remain under the detection limit of the technique. EXAFS (Extended X-ray Absorption Fine Structure) demonstrates the existence of G a − I n bonds in the alloys. The cation-anion bond-lengths in the alloys remain similar to that of the pure compounds. There is no signif…

Front Cover: High-pressure studies of topological insulators Bi2 Se3 , Bi2 Te3 , and Sb2 Te3 (Phys. Status Solidi B 4/2013)