Search for spin gapless semiconductors: The case of inverse Heusler compounds

We employ ab-initio electronic structure calculations to search for spin gapless semiconductors, a recently identified new class of materials, among the inverse Heusler compounds. The occurrence of this property is not accompanied by a general rule and results are materials specific. The six compounds identified show semiconducting behavior concerning the spin-down band structure and in the spin-up band structure the valence and conduction bands touch each other leading to 100% spin-polarized carriers. Moreover these six compounds should exhibit also high Curie temperatures and thus are suitable for spintronics applications.Comment: Submitted to Applied Physics Letter

Linear bands, zero-momentum Weyl semimetal, and topological transition in skutterudite-structure pnictides

It was reported earlier [Phys. Rev. Lett. 106, 056401 (2011)] that the skutterudite structure compound CoSb$_3$ displays a unique band structure with a topological transition versus a symmetry-preserving sublattice (Sb) displacement very near the structural ground state. The transition is through a massless Dirac-Weyl semimetal, point Fermi surface phase which is unique in that (1) it appears in a three dimensional crystal, (2) the band critical point occurs at $k$=0, and (3) linear bands are degenerate with conventional (massive) bands at the critical point (before inclusion of spin-orbit coupling). Further interest arises because the critical point separates a conventional (trivial) phase from a topological phase. In the native cubic structure this is a zero-gap topological semimetal; we show how spin-orbit coupling and uniaxial strain converts the system to a topological insulator (TI). We also analyze the origin of the linear band in this class of materials, which is the characteristic that makes them potentially useful in thermoelectric applications or possibly as transparent conductors. We characterize the formal charge as Co$^{+}$ $d^8$, consistent with the gap, with its $\bar{3}$ site symmetry, and with its lack of moment. The Sb states are characterized as $p_x$ (separately, $p_y$) $\sigma$-bonded $Sb_4$ ring states occupied and the corresponding antibonding states empty. The remaining (locally) $p_z$ orbitals form molecular orbitals with definite parity centered on the empty $2a$ site in the skutterudite structure. Eight such orbitals must be occupied; the one giving the linear band is an odd orbital singlet $A_{2u}$ at the zone center. We observe that the provocative linearity of the band within the gap is a consequence of the aforementioned near-degeneracy, which is also responsible for the small band gap.Comment: 10 pages, 7 figure

Oxide-Ion Thermopower of A/cceptor-Doped perovskites: The Impact of Inter-Defect Interactions

Received: 14 August 2025. Accepted: 26 August 2025. Published online: 29 August 2025.The effect of inter-defect interaction on the hopping thermopower in acceptor-doped oxides is considered on the example of wide-gap AIIB1−IVRIIIO3− perovskites with oxide-ion charge carriers. It is shown that acceptor-bound states of defects and inter-carrier correlations essentially affect and its dependence on dopant content and temperature even at low doping level. The method of determining the correct charge carriers concentration and heat of transport from thermopower data for such systems is discussed. The presented results can also be useful for understanding thermoelectric phenomena caused by other types of hopping charge carriers in various acceptor-doped oxides promising for electrochemical applications

Oxygen-Vacancy Transport in Acceptor-Doped Perovskites: Effective Medium Approximation Approach

Received: 14 August 2025. Accepted: 26 August 2025. Published online: 29 August 2025.A statistical theory, based on the effective medium approximation and master equation, is developed to describe oxygen-vacancy transport in AB1–xRxO3–δ perovskites taking into account inter-defect interactions. The role of acceptor-bound vacancy states and Fermi-type correlations is elucidated. The effects of inter-defect interaction on the dependence of oxygen-vacancy transport coefficients on dopant content and energetics of acceptor-bound states are established. Analytical findings are validated by Monte Carlo simulations, which also enable us to calculate the tracer diffusivity and determine the Haven ratio. The results can be useful for understanding transport phenomena in various acceptor-doped oxides promising for electrochemical applications

Semiconductor Thin Film Characterization with AC Surface Photovoltage

Abstract not Available.</jats:p