Exciton–polariton laser

We present a review of the investigations realized in the last decades of the phenomenon of the Bose–Einstein condensation (BEC) in the system of two-dimensional cavity polaritons in semiconductor nanostructures. The conditions at which the excitons interacting with cavity photons form new type of quasiparticles named as polaritons are described. Since polaritons can form in a microcavity a weakly interacting Bose gas, similarly to the exciton gas in semiconductors, the microcavity exciton–polariton BEC emerged in the last decades as a new direction of the exciton BEC in solids, promising for practical applications. The high interest in BEC of exciton–polaritons in semiconductor microcavities is related to the ultra-low threshold lasing which has been demonstrat-ed, in particular, for an electrically injected polariton laser based on bulk GaN microcavity diode working at room temperature

Pressure-induced band anticrossing in two adamantine ordered-vacancy compounds: CdGa2S4 and HgGa2S4

[EN] This paper reports a joint experimental and theoretical study of the electronic band structure of two ordered-vacancy compounds with defect-chalcopyrite structure: CdGa2S4 and HgGa2S4. High-pressure optical-absorption experiments (up to around 17 GPa) combined with first-principles electronic band-structure calculations provide compelling evidence of strong nonlinear pressure dependence of the bandgap in both compounds. The nonlinear pressure dependence is well accounted for by the band anticrossing model that was previously established mostly for selenides with defect chalcopyrite structure. Therefore, our results on two sulfides with defect chalcopyrite structure under compression provide definitive evidence that the nonlinear pressure dependence of the direct bandgap is a common feature of adamantine ordered-vacancy compounds and does not depend on the type of anion.This work was supported by the Spanish Ministry of Science, Innovation and Universities, the Spanish Research Agency (AEI), the European Fund for Regional Development (ERDF, FEDER) under grants PID2019-106383GB-C41/42 and RED2018-102612-T (MALTA Consolider-Team Network), and the Generalitat Valenciana under grant Prometeo/2018/123 (EFIMAT). This work also has received partial funding from the Horizon-2020 Spreading Excellence and Widening Participation research and innovation programme of the European Union under the grant #810652 (NanoMedTwin project). A.L. and D.E. would like to thank the Generalitat Valenciana for the Ph.D. fellowship GRISOLIAP/2019/025).Liang, A.; Shi, L.; Gallego-Parra, S.; Gomis, O.; Errandonea, D.; Tiginyanu, I.; Ursaki, V.... (2021). Pressure-induced band anticrossing in two adamantine ordered-vacancy compounds: CdGa2S4 and HgGa2S4. Journal of Alloys and Compounds. 886:1-8. https://doi.org/10.1016/j.jallcom.2021.1612261888

Structural and elastic properties of defect chalcopyrite HgGa2S4 under high pressure

In this work, we focus on the study of the structural and elastic properties of mercury digallium sulfide (HgGa2S4) at high pressures. This compound belongs to the family of AB(2)X(4) ordered-vacancy compounds and exhibits a tetragonal defect chalcopyrite structure. X-ray diffraction measurements at room temperature have been performed under compression up to 15.1 GPa in a diamond anvil cell. Our measurements have been complemented and compared with ab initio total energy calculations. The axial compressibility and the equation of state of the low-pressure phase of HgGa2S4 have been experimentally and theoretically determined and compared to other related ordered-vacancy compounds. The pressure dependence of the theoretical cation-anion and vacancy-anion distances and compressibilities in HgGa2S4 are reported and discussed in comparison to other related ordered-vacancy compounds. Finally, the pressure dependence of the theoretical elastic constants and elastic moduli of HgGa2S4 has been studied. Our calculations indicate that the low-pressure phase of HgGa2S4 becomes mechanically unstable above 13.8 GPa. (C) 2013 Elsevier B. V. All rights reserved.This study was supported by the Spanish government MEC under Grants No: MAT2010-21270-C04-01/03/04 and CTQ2009-14596-C02-01, by the Comunidad de Madrid and European Social Fund (S2009/PPQ-1551 4161893), by MALTA Consolider Ingenio 2010 Project (CSD2007-00045), by Generalitat Valenciana (GVA-ACOMP-2013-1012), and by the Vicerrectorado de Investigacion y Desarrollo of the Universidad Politecnica de Valencia (UPV2011-0914 PAID-05-11 and UPV2011-0966 PAID-06-11). E.P-G., A. M., and P.R-H. acknowledge computing time provided by Red Espa ola de Supercomputacion (RES) and MALTA-Cluster. J.A.S. acknowledges Juan de la Cierva fellowship program for financial support.Gomis Hilario, O.; Santamaría-Pérez, D.; Vilaplana Cerda, RI.; Luna Molina, R.; Sans, JA.; Manjón Herrera, FJ.; Errandonea, D.... (2014). Structural and elastic properties of defect chalcopyrite HgGa2S4 under high pressure. Journal of Alloys and Compounds. 583:70-78. https://doi.org/10.1016/j.jallcom.2013.08.123S707858

Nanoporous membranes and heterostructures on III-V compounds for micro- and optoelectronic applications

High-quality nanoporous membranes and heterostructures of III-V compounds have been fabricated by using MeV-ion-implantation-assisted or photon-assisted electrochemical etching. They were found to exhibit short-wavelength luminescence, Fröhlich-type surface-related vibrations and enhanced nonlinear optical response. The obtained results are discussed in connection with various possible applications of nanoporous structures