Thermoelectric energy harvesting-the transformation of waste heat into useful electricity-is of great interest for energy sustainability. The main obstacle is the low thermoelectric efficiency of materials for converting heat to electricity, quantified by the thermoelectric figure of merit, ZT. The best available n-type materials for use in mid-temperature (500-900 K) thermoelectric generators have a relatively low ZT of 1 or less, and so there is much interest in finding avenues for increasing this figure of merit. Here we report a binary crystalline n-type material, In(4)Se(3-delta), which achieves the ZT value of 1.48 at 705 K-very high for a bulk material. Using high-resolution transmission electron microscopy, electron diffraction, and first-principles calculations, we demonstrate that this material supports a charge density wave instability which is responsible for the large anisotropy observed in the electric and thermal transport. The high ZT value is the result of the high Seebeck coefficient and the low thermal conductivity in the plane of the charge density wave. Our results suggest a new direction in the search for high-performance thermoelectric materials, exploiting intrinsic nanostructural bulk properties induced by charge density waves.

Pure lead-free SnTe has limited thermoelectric potentials because of the low Seebeck coefficients and the relatively large thermal conductivity. In this study, we provide experimental evidence and theoretical understanding that alloying SnTe with Ca greatly improves the transport properties leading to ZT of 1.35 at 873 K, the highest ZT value so far reported for singly doped SnTe materials. The introduction of Ca (0–9%) in SnTe induces multiple effects: (1) Ca replaces Sn and reduces the hole concentration due to Sn vacancies, (2) the energy gap increases, limiting the bipolar transport, (3) several bands with larger effective masses become active in transport, and (4) the lattice thermal conductivity is reduced by about 70% due to the contribution of concomitant scattering terms associated with the alloy disorder and the presence of nanoscale precipitates. An efficiency of ∼10% (for ΔT = 400 K) was predicted for high-temperature thermoelectric power generation using SnTe-based p- and n-type materials.

A LiFeAs single crystal with T onset c ∼19.7 K was grown successfully in a sealed tungsten crucible using the Bridgeman method. The electrical resistivity experiments revealed a ratio of room temperature to residual resistivity (RRR) of approximately 46 and 18 for the in-plane and out-of plane directions. The estimated anisotropic resistivity, γρ=ρc/ρ ab , was approximately 3.3 at T onset c . The upper critical fields had large H ab c2 and H c c2 values of 83.4 T and 72.5 T, respectively, and an anisotropy ratio is γH =H ab c2 /H c c2 ∼1.15. The high upper critical field value and small anisotropy highlight the potential use of LiFeAs in a variety of applications. The calculated critical current density (Jc) from the M -H loop is approximately 10 3 A/cm 2

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We report the high thermoelectric figure-of-merit (ZT) on the Se-deficient polycrystalline compounds of In4Se3−x (0.02≤x≤0.5) and the anisotropic electronic band structure. The Se-deficiency (x) has the effect of decreasing the semiconducting band gap and increasing the power factor. The band structure calculation for In4Se3−x (x=0.25) exhibits localized hole bands at the Γ-point and Y-S symmetry line, whereas the significant electronic band dispersion is observed along the c-axis. Here, we propose that the high ZT values on those compounds are originated from the anisotropic electronic band structure as well as Peierls distortion.

Large-area and highly crystalline CVD-grown multilayer MoSe2 films exhibit a well-defined crystal structure (2H phase) and large grains reaching several hundred micrometers. Multilayer MoSe2 transistors exhibit high mobility up to 121 cm(2) V(-1) s(-1) and excellent mechanical stability. These results suggest that high mobility materials will be indispensable for various future applications such as high-resolution displays and human-centric soft electronics.

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We report on magnetization M (H), dc/ac magnetic susceptibility χ(T ), specific heat Cm(T ) and muon spin relaxation (µSR) measurements of the Kitaev honeycomb iridate Cu2IrO2 with quenched disorder. In spite of the chemical disorders, we find no indication of spin glass down to 260 mK from the Cm(T ) and µSR data. Furthermore, a persistent spin dynamics observed by the zero-field muon spin relaxation evidences an absence of static magnetism. The remarkable observation is a scaling relation of χ[H, T ] and M [H, T ] in H/T with the scaling exponent α = 0.26 − 0.28, expected from bond randomness. However, Cm[H, T ]/T disobeys the predicted universal scaling law, pointing towards the presence of low-lying excitations in addition to random singlets. Our results signify an intriguing role of quenched disorder in a Kitaev spin system in creating low-energy excitations possibly pertaining to Z2 fluxes.The exactly solvable Kitaev honeycomb model provides a novel route to achieve elusive topological and quantum spin liquids [1,2].Exchange frustration of bond-dependent Ising interactions fractionalizes the j eff = 1 2 spin into itinerant Majorana fermion and static Z 2 gauge flux [3][4][5]. Edge-sharing of octahedrally coordinated metal ions subject to strong spin-orbit coupling supports the realization of Kitaev-type interactions [6][7][8].In the quest for a Kitaev honeycomb magnet, the family of A 2 IrO 3 (A = Na, Li) and α-RuCl 3 are considered prime candidate materials [9][10][11][12][13][14][15][16]. In these compounds, however, the theoretically predicted spin-liquid state is preempted by long-range magnetic order due to structural imperfections. As the real materials are vulnerable to a monoclinic stacking of honeycomb layers, non-Kitaev terms seem inevitable. A related issue is to engineer local crystal environments towards an optimal geometry to maximize the Kitaev interactions.Very recently, the new Kitaev honeycomb iridates H 3 LiIr 2 O 6 and Cu 2 IrO 3 have been derived from their ancestors A 2 IrO 3 through soft structural modifications [17,18]. H 3 LiIr 2 O 6 is obtained by replacing the interlayer Li + ions with H + from α-Li 2 IrO 3 , while the honeycomb layer remains intact. A scaling of the specific heat and NMR relaxation rate gives evidence for the presence of fermionic excitations [17]. In stabilizing a Kitaev-like spin liquid, hydrogen disorders turn out to a key ingredient by enhancing Kitaev exchange interactions and promoting spin disordering [19,20]. In case of Cu 2 IrO 3 , all of the A-site cations of Na 2 IrO 3 are permuted by Cu + ions. Consequently, in-plane bond disorders become significant in determining magnetic behavior. Figure 1(a) presents the crystal structure of Cu 2 IrO 3