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High-$T_{\rm C}$ superconductors show anomalous transport properties in their normal states, such as the bad-metal and pseudogap behaviors. To discuss their origins, it is important to speculate whether these behaviors are…
We report X-ray diffraction, magnetization and transport measurements for polycrystalline samples of the new layered superconductor Bi4-xAgxO4S3 (0<x<0.2). The superconducting transition temperature (TC) decreases gradually and finally…
The thermoelectric characteristics of lead selenium (PbSe) doped with gallium (Ga) are investigated in this study. When the lead sulfide (PbSe) is tuned with appropriate dopants, it exhibits satisfactory ZT values, hence making it a…
A new doping mechanism is described, whereby a doping impurity does not simply transfer charge to the bands of a host semiconductor or semimetal, but rearranges the core energy levels deep in the valence band of the host. This, in turn,…
Bystroem-Evers compound Ag5 Pb2O6 has been annealed at 500-540 K under flow of electric current which results in a textured structure and anisotropic colossal electric conductivity (> 10^9 ohm-1cm-1) between 210-525 K. The related physical…
Two-dimensional (2D) $\beta$-TeO$_2$ has gained attention as a promising material for optoelectronic and power device applications, thanks to its transparency and high hole mobility. However, the underlying mechanism behind its $p$-type…
We report accurate energetics of defects introduced in GaN on doping with divalent metals, focussing on the technologically important case of Mg doping, using a model which takes into consideration both the effect of hole localisation and…
A material which is an insulator entirely because of interaction effects is called a correlated insulator. Examples are trans-polyacetylene and the cuprate high temperature superconductors. Whereas doping of a band insulator results in a…
We report the electronic properties of single crystals of candidate nodal-line semimetal CaAgP. The transport properties of CaAgP are understood within the framework of a hole-doped nodal-line semimetal. In contrast, Pd-doped CaAgP shows a…
We report first-principles microscopic calculations of the formation energy, electrical activity, and magnetic moment of Co dopants and a variety of native defects in TiO2 anatase. Using these results, we use equilibrium thermodynamics to…
N-type doping in Si by shallow impurities, such as P, As and Sb, exhibits an intrinsic limit due to the Fermi-level pinning via defect complexes at high doping concentrations. Here we demonstrate that doping Si with the chalcogen Te by…
$\beta$-Ga$_2$O$_3$ is a leading ultra-wide band gap semiconductor, but its performance depends on precise control over dopant incorporation and stability. In this work, we use first-principles calculations to systematically assess the…
Recent evidence for a charge-Kondo effect in superconducting samples of Pb$_{1-x}$Tl$_x$Te [1] has brought renewed attention to the possibility of negative U superconductivity in this material, associated with valence fluctuations on the Tl…
BaTiO3 is typically a strong n-type material with tuneable optoelectronic properties via doping and controlling the synthesis conditions. It has a wide band gap that can only harness the ultraviolet region of the solar spectrum. Despite…
This paper reports the effect of Ag-doping on electrical properties of a-Sb2Se3 in the temperature range 240-340 K and frequency range 5 Hz to 100 kHz. The variation of transport properties with thermal doping has been studied. Ag-doping…
Enthalpies of formation of gallium interstitials and all the other native point defects in gallium arsenide are calculated using the same well-converged \emph{ab initio} techniques. Using these results, equilibrium concentrations of these…
We investigate the properties of PbTe doped with a small concentration $x$ of Tl impurities acting as acceptors and described by Anderson impurities with negative onsite correlation energy. We use the numerical renormalization group method…
We investigate the self-compensation mechanism in phosphorus-doped CdTe. The formation energies, charge transition levels, and defects states of several P-related point defects susceptible to cause self-compensation are addressed by…
We report on the thermoelectric properties of nickel doped Ag2-xNixTe (x = 0, 0.015, 0.025 & 0.055, 0.115, 0.155) nanostructures in the temperature (T) range of 5 K to 575 K. The electrical resistivity of Ag2Te nanostructure shows metallic…
Understanding the detailed electronic structure of deep defect states in narrow band-gap semiconductors has been a challenging problem. Recently, self-consistent ab initio calculations within density functional theory (DFT) using supercell…