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Tuning the properties of magnetic topological materials is of interest to realize exotic physical phenomena, new quantum phases and quasiparticles, and topological spintronic devices. However, current topological materials exhibit Curie temperature (TC) values far below those needed for practical applications. In recent years, significant progress has been made to control and optimize TC, particularly through defect-engineering of these structures. Most recently, we reported TC values up to 80 K for (MnSb2Te4)x(Sb2Te3)1−x when 0.7 ≤ x ≤ 0.85 by controlling the composition x and the Mn content in these structures during molecular beam epitaxy growth. In this study, we show further enhancement of the TC, as high as 100 K, by maintaining high Mn content and reducing the growth rate from 0.9 nm/min to 0.5 nm/min. Derivative curves of the Hall resistance and the magnetization reveal the presence of two TC components contributing to the overall value and suggest TC1 and TC2 have distinct origins: excess Mn in MnSb2Te4 septuple layers (SLs) and high Mn content in Sb2−yMnyTe3 quintuple layer (QL) alloys, respectively. To elucidate the mechanisms promoting higher TC values in this system, we show evidence of enhanced structural disorder due to the excess Mn that occupies not only Sb sites but also Te sites, leading to the formation of a new crystal structure for these materials. Learning to control defects that enhance desired magnetic properties and understanding the mechanisms that promote high TC in magnetic topological materials such as (Mn1+ySb2−yTe4)x(Sb2−yMnyTe3)1−x is of great importance to achieve practical quantum devices. [ABSTRACT FROM AUTHOR]

We measured the photoluminescence (PL) of single CsPbBr3 nanocrystals (NCs) that have a highly anisotropic shape and orthorhombic crystal phase. As the thickness of these NCs is much more smaller than the other two dimensions, they are also called nanoplatelets (NPLs). We obtain PL spectra characterized by doublets separated in energy by about 2 meV in average and showing orthogonal and linearly polarized polar lines. We identified these doublets as the two bright-exciton states of the exciton fine structure contained in the plane of the NPLs. By a comparison between theory and experiments, we were able to obtain fundamental parameters as tetragonal and orthorhombic crystal field. We measured and analysed the time-resolved PL evolution as a function of temperature of small ensemble of NPLs. We thus succeed at framing the experimental value of the bright-dark exciton splitting (5-7meV) that is slightly smaller than the theoretical value.

Magnetic topological materials are promising for realizing novel quantum physical phenomena. Among these, bulk Mn-rich MnSb2Te4 is ferromagnetic due to MnSb antisites and has relatively high Curie temperatures (TC), which is attractive for technological applications. We have previously reported the growth of materials with the formula (Sb2Te3)1−x(MnSb2Te4)x, where x varies between 0 and 1. Here we report on their magnetic and transport properties. We show that the samples are divided into three groups based on the value of x (or the percent septuple layers within the crystals) and their corresponding TC values. Samples that contain x < 0.7 or x > 0.9 have a single TC value of 15–20 K and 20–30 K, respectively, while samples with 0.7 < x < 0.8 exhibit two TC values, one (TC1) at ~ 25 K and the second (TC2) reaching values above 80 K, almost twice as high as any reported value to date for these types of materials. Structural analysis shows that samples with 0.7 < x < 0.8 have large regions of only SLs, while other regions have isolated QLs embedded within the SL lattice. We propose that the SL regions give rise to a TC1 of ~ 20 to 30 K, and regions with isolated QLs are responsible for the higher TC2 values. Our results have important implications for the design of magnetic topological materials having enhanced properties. [ABSTRACT FROM AUTHOR]

In this work, we studied, at low temperature, the coherent evolution of the localized electron and hole spins in a polycrystalline film of CH3NH3PbI3 (MAPI) by using a picosecond-photo-induced Faraday rotation technique in an oblique magnetic field. We observed an unexpected anisotropy for the electron and hole spin. We determined the electron and hole Landé factors when the magnetic field was applied in the plane of the film and perpendicular to the exciting light, denoted as transverse ⊥   factors, and when the magnetic field was applied perpendicular to the film and parallel to the exciting light, denoted as parallel   ∥   factors. We obtained | g e , ⊥ | = 2.600   ±   0.004 , | g e , ∥ | = 1.604   ±   0.033 for the electron and | g h , ⊥ | = 0.406   ±   0.002 , | g h , ∥ | = 0.299   ±   0.007 for the hole. Possible origins of this anisotropy are discussed herein. [ABSTRACT FROM AUTHOR]

The 17th International Conference on II-VI Compounds and Related Materials was held at the Campus des Cordeliers, in the historical center of Paris, France, from September 13th to 18th. II-VI 2015 has followed the path of a suc-cessful series of biennial conferences which started in Durham (UK) in 1983. Recent conferences were or-ganized in Niagara Falls (USA, 2003), Warsaw (Po-land, 2005), Jeju (Korea, 2007), Saint Petersburg (Russia, 2009), Mayan (Mexico, 2011), and Na-gahama (Japan, 2013). The II-VI conference aims at providing an international forum for scientists, students and indus-try representatives, facilitating the exchange of new ideas and establishing fructuous scientific contacts. The ambition is to report the newest developments in basic and applied research on II-VI and re-lated compounds such as oxides and chalcopyrite semiconductors. The topics cover also novel synthe-sis techniques, new physical properties and innova-tive device development. Let us note that for this last edition, the scope has been extended to Related Mate-rials like photovoltaic materials and novel 2D sys-tems (dichalcogenides and topological insulators). Gathering 240 participants, II-VI Paris 2015 has fulfilled its mission, with a scientific pro-gram presenting three plenary review lectures, 15 in-vited talks, 64 contributed talks and about 200 con-tributed poster presentations. A special session has been devoted to the memory of Prof. Fritz Henneber-ger from Humboldt University, Berlin. Following the conference, this issue of physica status solidi offers a variety of basic and applied studies on optical, electrical and mag-netic properties of II-VI compounds, related materials and devices. Achievements in practical ap-plications of II-VI compounds will be found in infrared, visible and UV range detectors, optoelec-tronic devices, photovoltaics. The proceedings edition also emphasizes new trends and pioneering directions, towards original related materials and devices. A total of 78 articles are published in pss ( b) (11), pss RRL (1) and pss ( c) (66). We wish that all participants would appreciate to redis-cover and thoroughly read some of the nice results presented in Paris. We thank all contributors and reviewers who made the edition of II-VI Paris Proceedings a great success and hope the conference as well as the unique atmosphere of Paris will remain in your heart and memory! [ABSTRACT FROM AUTHOR]

In the semiconducting perovskite materials family, the cesium-lead-chloride compound (CsPbCl 3 ) supports robust excitons characterized by a blue-shifted transition and the largest binding energy, thus presenting a high potential to achieve demanding solid-state room-temperature photonic or quantum devices. Here we study the fundamental emission properties of cubic-shaped colloidal CsPbCl 3 nanocrystals (NCs), examining in particular individual NC responses using micro-photoluminescence in order to unveil the exciton fine structure (EFS) features. Within this work, NCs with average dimensions ⟨ L α ⟩ ≈ 8 nm (α = x , y , z ) are studied with a level of dispersity in their dimensions that allows disentangling the effects of size and shape anisotropy in the analysis. We find that most of the NCs exhibit an optical response under the form of a doublet with crossed polarized peaks and an average inter-bright-state splitting, Δ BB ≈ 1.53 meV, but triplets are also observed though being a minority. The origin of the EFS patterns is discussed in the frame of the electron-hole exchange model by taking into account the dielectric mismatch at the NC interface. The different features (large dispersity in the Δ BB values and occasional occurrence of triplets) are reconciled by incorporating a moderate degree of shape anisotropy, observed in the structural characterization, by preserving the relatively high degree of the NC lattice symmetry. The energy distance between the optically inactive state and the bright manifold, Δ BD , is also extracted from time-resolved photoluminescence measurements (Δ BD ≈ 10.7 meV), in good agreement with our theoretical predictions.

We synthesized strongly anisotropic CsPbBr 3 nanocrystals with very narrow emission and absorption lines associated to confinement effects along one or two dimensions, called respectively nanoplatelets (NPLs) and nanosticks (NSTs). Transmission Electron Microscopy (TEM) images, absorption and photoluminescence (PL) spectra taken at low temperature are very precise tools to determine which kind of confinement has to be considered and to deduce the shape, the size and the thickness of nanocrystals under focus. We show that the energy of the band-edge absorption and PL peaks versus the inverse of the square of the NPL thickness has a linear behaviour from 11 monolayers (MLs) i.e. a thickness of 6.38 nm, until 4 MLs (2.32 nm) showing that self-energy correction compensates the increase of the exciton binding energy in thin NPLs as already observed in Cadmium chalcogenides-based NPLs. We also show that slight changes in the morphology of NSTs leads to a very drastic modification of their absorption spectra. Time-resolved PL of NSTs has a non-monotonous behaviour with temperature. At 5 K, a quasi-single exponential with a lifetime of 80 ps is obtained; at intermediate temperature, the decay is bi-exponential and at 150 K, a quasi-single exponential decay is recovered (≈0.4 ns). For NSTs, the exciton interaction with LO phonons governs the broadening of the absorption and PL peaks at room temperature and is stronger than in chalcogenides quantum dots and NPLs.