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A. A. Hovhannisyan

Publications and source records attributed to A. A. Hovhannisyan.

6 recordsLinked to original sources

Polyvinylpyrrolidone planarized liquid crystalline 1T-WS2/rGO hybrid nanocomposites-based humidity sensing platform

Two-dimensional hybrid nanocomposites combining graphene-like materials and transition metal dichalcogenides (TMDCs) are created using various synthesis methods and are vital for environmental sensing due to the synergistic effects of their components. These hybrid materials offer enhanced sensitivity, selectivity, surface-to-volume ratio, tunable electronic properties, strong interaction with analytes, and fast detection capabilities, which address the limitations of individual materials. This is due to their outstanding surface-to-volume ratio, tunable electronic properties, strong interactions with analytes, as well as their high sensitivity, selectivity, and fast detection capabilities, which are crucial for environmental sensing. Herein, a hydrothermally synthesized and polyvinylpyrrolidone (PVP)-stabilized 1T phase tungsten disulfide/reduced graphene oxide, 1T-WS2/PVP/rGO, hybrid nanocomposite is reported. The intrinsic liquid crystalline behavior of the synthesized composite enables the formation of highly uniform films for effective humidity sensing. The optostructural characterization and key performance parameters, including response and recovery times, of the 1T-WS2/PVP/rGO hybrid nanocomposite-based structure are comprehensively analyzed and studied. This is the first to report on the synthesis of a 1T-WS2/PVP/rGO hybrid nanocomposite, its liquid crystalline phase formation, and application in humidity sensing. The proposed sensing platform introduces a novel approach to humidity sensing using 1T-WS2/PVP/rGO liquid crystalline films, which combine the metallic advantages of 1T-WS2, the stabilizing role of PVP and the conductive framework of rGO into aligned LC structures for enhanced sensitivity, rapid response and environmental robustness.

physics.app-ph↗

Self-oscillating open quantum systems

Evolution of occupation number is studied for a bosonic oscillator (with one and two degrees of freedom) linearly fully coupled to fermionic and bosonic heat baths. The lack of equilibrium in this oscillator is discussed in the light of the creation of an energy source. The connection of such a system with known nonlinear self-oscillating systems is shown.

quant-ph↗

New type of self-oscillating systems

The time evolution of occupation number is studied for a bosonic oscillator (with one and two degrees of freedom) linearly fully coupled to fermionic and bosonic heat baths. The absence of equilibrium in this oscillator is discussed as a tool to create a dynamical non-stationary memory storage. The connection between such a system and the well-known nonlinear self-oscillating systems is demonstrated.

quant-ph↗

Casimir effect for fermion condensate in conical rings

The fermion condensate (FC) is investigated for a (2+1)-dimensional massive fermionic field confined on a truncated cone with an arbitrary planar angle deficit and threaded by a magnetic flux. Different combinations of the boundary conditions are imposed on the edges of the cone. They include the bag boundary condition as a special case. By using the generalized Abel-Plana-type summation formula for the series over the eigenvalues of the radial quantum number, the edge-induced contributions in the FC are explicitly extracted. The FC is an even periodic function of the magnetic flux with the period equal to the flux quantum. Depending on the boundary conditions, the condensate can be either positive or negative. For a massless field the FC in the boundary-free conical geometry vanishes and the nonzero contributions are purely edge-induced effects. This provides a mechanism for time-reversal symmetry breaking in the absence of magnetic fields. Combining the results for the fields corresponding to two inequivalent irreducible representations of the Clifford algebra, the FC is investigated in the parity and time-reversal symmetric fermionic models and applications are discussed for graphitic cones.

hep-th↗

Applicability of the absence of equilibrium in quantum system fully coupled to several fermionic and bosonic heat baths

The time evolution of occupation number is studied for fermionic or bosonic oscillator linearly fully coupled to several fermionic and bosonic heat baths. The influence of characteristics of thermal reservoirs of different statistics on the non-stationary population probability is analyzed at large times. Applications of the absence of equilibrium in such systems for creating a dynamic (nonstationary) memory storage are discussed.

quant-ph↗

Non-Markovian modeling of Fermi-Bose systems coupled to one or several Fermi-Bose thermal baths

A method is proposed to describe Fermi or Bose systems coupled to one or several heat baths composed of fermions and/or bosons. The method, called Coupled Equations of Motion method, properly includes non-Markovian effects. The approach is exact in the Full-Coupling approximation when only bosonic particles are present in the system and baths. The approach provides an approximate treatment when fermions are present either in the system and/or in one or several environments. The new approach has the advantage to properly respect the Pauli exclusion principle for fermions during the evolution. We illustrate the approach for the single Fermi or Bose two-level system coupled to one or two heat-baths assuming different types of quantum statistics (Fermion or Bosons) for them. The cases of Fermi system coupled to fermion or boson heat baths or a mixture of both are analyzed in details. With the future goal to treat Fermi systems formed of increasing number of two-level systems (Qubits), we discuss possible simplifications that could be made in the equations of motion and their limits of validity in terms of the system--baths coupling or of the initial heat baths temperatures.

quant-ph↗