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By means of angle-resolved photoemission spectroscopy (ARPES) measurements, we unveil the electronic band structure of three-dimensional PbBi6Te10topological insulator. ARPES investigations evidence multiple coexisting Dirac surface states at the zone-center of the reciprocal space, displaying distinct electronic band dispersion, different constant energy contours, and Dirac point energies. We also provide evidence of Rashba-like split states close to the Fermi level, and deeper M- and V-shaped bands coexisting with the topological surface states. The experimental findings are in agreement with scanning tunneling microscopy measurements revealing different surface terminations according to the crystal structure of PbBi6Te10. Our experimental results are supported by density functional theory calculations predicting multiple topological surface states according to different surface cleavage planes.

In this paper, the authors report first‐principles calculations of the Seebeck coefficient in TlInSe2. Experimental measurements demonstrate that TlInSe2is characterized by giant values of the Seebeck coefficient at the temperature region of 320–430 K. To get insight on significant enhancement of Seebeck coefficient under temperature changing the density functional theory (DFT) and the Boltzmann transport equation are applied to calculate the semiclassical transport coefficients for TlInSe2and its constructed models. The molecular dynamic simulations of 2 × 2 × 2 and 1 × 1 × 8 superlattices of TlInSe2, the TlInSe2_118a, TlInSe2_118b, TlInSe2_222a, TlInSe2_222b structures are performed to study their behavior in both “bulk” and “chain – like” modes. It is found that the distortions of InSe4tetrahedra and displacements of Tlatom lead to formation of Tl–Se covalent bonds. The “bulk” TlInSe2_222b compound possesses the maximum value of Seebeck coefficient and (ZT)maxin comparison with another studied compounds. The hybridization of Se and Tl orbitals near the top of valence band and hybridization of the Se, Tl, and In orbitals in conduction band may lead to increasing of Seebeck coefficient in TlInSe2at 425 K. Crystal structure models of TlInSe2: On the left hand side it can be seen that the structure corresponds to the tetragonal structure with space group D4h18; and on the right‐hand side is the structural model of incommensurate phase.

Seebeck Coefficients In article number 1800835, Yurii M. Chumakov, MirHasan Yu. Seyidov, and co‐workers report first‐principles calculations of the Seebeck coefficient in TlInSe2. The hybridization of Se and Tl orbitals near the top of valence band as well as Se, Tl, and In orbitals in conduction band may lead to giant values of the Seebeck coefficient as it is reported in literature.

The first observation of laser oscillation from a single crystal of CaGa2S4:Eu2+(1 at%) is described in this report. A liquid nitrogen cooled thin platelet (0.8 mm thick), whose one flat surface was coated with aluminum to increase the reflectivity, was excited from the other uncoated side with a pulsed dye laser beam having a photon energy of around 2.48 eV. When the input power density exceeded a threshold value of ?10 MW/cm2, a directional beam having a sharp spectral line at around 2.19 eV emerged from the sample. This laser was found to have interesting wavelength tunability extending to ?200 Å, possibly related to the broad gain spectrum of Eu2+emission in this material.