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Mark Auslender

Publications and source records attributed to Mark Auslender.

12 recordsLinked to original sources
arXiv2019

Upmost efficiency, few-micron-sized midwave infrared HgCdTe photodetectors

A few-micron thick structure that shows nearly 100% resonant polarized absorptance at a predefined midinfrared wavelength is designed and simulated. Like resonant-cavity enhanced photodetector structure, it contains a thin absorber enclosed in a dielectric cavity but surrogates the mirrors by two grating-on-layer structures. Fair manufacturing tolerance while maintaining high peak efficiency is proved. Electromagnetic fields amplitudes and Poynting vector over the cavity-absorber area are visualized and topology of electromagnetic power flow for two linear polarizations is discussed.

physics.optics↗
arXiv2012

IR color separation in transmission through gratings on (110) silicon: FTIR experiment versus theory

The phenomenon of filtering in zero-diffraction order is studied for transmission through 1D-periodic structures on a silicon wafer. Our study combines FTIR spectrometry in the range from 2.5 to 25 microns, and a rigorous full-vector simulation. The phenomenon exhibits itself as 'bright' and 'dark' bands in the spectra of normal transmission through grating samples, which replace each other quasi-periodically with respect to wave number, at wavelengths smaller than the grating period. The transmission modulation ratio is extremely high for two-side polished samples. Good agreement between the rigorous theory and experiment both in the range of the transmission oscillations and in the region of enhanced absorption is obtained

physics.optics↗
arXiv2012

New resonant cavity-enhanced absorber structures for mid-infrared detector application

A new dielectric Fabry-Perot cavity was designed for a resonant enhancing optical absorption by a thin absorber layer embedded into the cavity. In this cavity, the front mirror is a subwavelength grating with $\sim 100$% retroreflection. For a HgCdTe absorber in a matching cavity of the new type, the design is shown to meet the combined challenges of increasing the absorbing efficiency of the entire device up to $\sim 100$% and reducing its size and overall complexity, compared to a conventional resonant cavity enhanced HgCdTe absorber, while maintaining a fairly good tolerance against the grating's fabrication errors.

physics.optics↗
arXiv2002

Ferromagnetic transition in a double-exchange model

We calculate the temperature of a ferromagnetic transition in a double-exchange model with classical core spins for arbitrary relation between Hund exchange coupling and electron band width by solving the Dynamical Mean Field Approximation equations.

cond-mat.stat-mech↗
arXiv2002

Ground state of a double-exchange system containing impurities: bounds of ferromagnetism

We study the boundary between ferromagnetic and non-ferromagnetic ground state of a double-exchange system with quenched disorder for arbitrary relation between Hund exchange coupling and electron band width. The boundary is found both from the solution of the Dynamical Mean Field Approximation equations and from the comparison of the energies of the saturated ferromagnetic and paramagnetic states. Both methods give very similar results. To explain the disappearance of ferromagnetism in part of the parameter space we derive from the double-exchange Hamiltonian with classical localized spins in the limit of large but finite Hund exchange coupling the $t-J$ model (with classical localized spins).

cond-mat.str-el↗
arXiv2002

Ferromagnetic transition in a double-exchange system containing impurities in the Dynamical Mean Field Approximation

We formulate the Dynamical Mean Field Approximation equations for the double-exchange system with quenched disorder for arbitrary relation between Hund exchange coupling and electron band width. Close to the ferromagnetic-paramagnetic transition point the DMFA equations can be reduced to the ordinary mean field equation of Curie-Weiss type. We solve the equation to find the transition temperature and present the magnetic phase diagram of the system.

cond-mat.stat-mech↗
arXiv2001

Ferromagnetic transition in a double-exchange system with alloy disorder

We study ferromagnetic transition in three-dimensional double-exchange model containing impurities. The influence of both spin fluctuations and impurity potential on conduction electrons is described in coherent potential approximation. In the framework of thermodynamic approach we construct Landau functional for the system "electrons (in disordered environment) + core spins". Analyzing the Landau functional we calculate the temperature of ferromagnetic transition $T_C$ and paramagnetic susceptibility $χ$. For $T_C$, we thus extend the result obtained by Furukawa in the framework of the Dynamical Mean Field Approximation, with which our result coincides in the limit of zero impurity potential. We find, that the alloy disorder, able to produce a gap in density of electron states, can substantially decrease $T_C$ with respect to the case of no impurities. We also study the general relation between the Coherent Potential Approximation and the Dynamical Mean Field Approximation.

cond-mat.str-el↗
arXiv2001

Ferromagnetic transition in a double-exchange system

We study ferromagnetic transition in three-dimensional double-exchange model. The influence of strong spin fluctuations on conduction electrons is described in coherent potential approximation. In the framework of thermodynamic approach we construct for the system "electrons (in a disordered spin configuration) + spins" the Landau functional, from the analysis of which critical temperature of ferromagnetic transition is calculated.

cond-mat.stat-mech↗
arXiv2001

CPA density of states and conductivity in a double-exchange system containing impurities

We study density of states and conductivity of the doped double-exchange system, treating interaction of charge carriers both with the localized spins and with the impurities in the coherent potential approximation. It is shown that under appropriate conditions there is a gap between the conduction band and the impurity band in paramagnetic phase, while the density of states is gapless in ferromagnetic phase. This can explain metal-insulator transition frequently observed in manganites and magnetic semiconductors. Activated conductivity in the insulator phase is numerically calculated.

cond-mat↗
arXiv1999

Localization and Dephasing Driven by Magnetic Fluctuations in Low Carrier Density Colossal Magnetoresistance Materials

Localization and dephasing of conduction electrons in a low carrier density ferromagnet due to scattering on magnetic fluctuations is considered. We claim the existence of the "mobility edge", which separates the states with fast diffusion and the states with slow diffusion; the latter is determined by the dephasing time. When the "mobility edge" crosses the Fermi energy a large and sharp change of conductivity is observed. The theory provides an explanation for the observed temperature dependence of conductivity in ferromagnetic semiconductors and manganite pyrochlores.

cond-mat.str-el↗
arXiv1998

Anderson localization due to spin disorder: a driving force of temperature-dependent metal-semiconductor transition in colossal-magnetoresistance materials

We study temperature induced metal-insulator transition in doped ferromagnetic semiconductors, described by s-d exchange model. The transition is a result of the mobility edge movement, the disorder being due to magnetic ions spin density fluctuations. The electrons are described in the tight binding approximation. Using ideas and methods of Anderson localization theory we obtain simple formulas, which connect the mobility edge with short-range order characteristics of the magnetic subsystem -- static spin correlators. We discuss the application of the theory to several groups of novel colossal-magnetoresistance materials and include the reproduction of the paper [E. M. Kogan and M. I. Auslender, phys. stat. sol. (b) vol. 147, 613 (1988)] published by us 10 years ago.

cond-mat↗