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Journal of Physics: Condensed Matter - latest papers

Latest articles for Journal of Physics: Condensed Matter

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  • Quantum thermoelectrics in closed circuit with non-equilibrium electrons
    The influence of a non-equilibrium classical environment on the parameters of a quantum heat converter in a closed circuit at a given (non-zero) output power is theoretically investigated. It is shown that the non-equilibrium of the electron distribution function in metal terminals contributes to the kinetic coefficients of the linear approximation. Analytical expressions of the Seebeck and Peltier coefficients are obtained, considering the non-equilibrium in the terminals when electric current and heat flow through the system. The influence of non-equilibrium on the theoretical power limit and efficiency of the heat engine at a fixed output power is also determined. Closed-form solutions were obtained for the quantum bound of the heat engine output power and the theoretical limit of the heat conversion efficiency at a given output power in quantum systems with a non-equilibrium environment for certain limited cases. A spectroscopic thermoelectric method for studying quantum systems is proposed.

  • The electronic, stability and mechanical properties of the kagome lattice CsTi3Bi5 under pressure: a first-principles study
    The kagome lattices of the ATi3Bi5 family have recently garnered significant attention due to their superconducting and topological properties. Here, we conducted an in-depth analysis of the band structure of the prototypical titanium-based kagome lattice material, CsTi3Bi5, using Density Functional Theory. We revealed its topological properties and demonstrated that the Van Hove singularities can be effectively tuned to the Fermi level under 18 GPa. Our findings confirm the dynamic stability of the CsTi3Bi5 system and further demonstrate that its elastic constants, which comply with Born’s criteria, ensure mechanical stability. The Poisson’s ratio and Pugh’s ratio indicate good ductility, while the material exhibits relatively low hardness. Notably, the mechanical properties exhibit significant directional anisotropy under all pressure conditions. As a key material in kagome lattices, the research results on CsTi3Bi5 provide theoretical insights for experimental studies and the preparation of similar materials.

  • Magnetic, thermoelectric, and electrical transport properties of CsMn4As3
    The present investigation utilized first-principles methodologies to elucidate the electronic and magnetic characteristics of bulk CsMn4As3. Our results validate the Mott insulator behavior of this compound, which is in agreement with the existing literature. Through the application of the Heisenberg spin Hamiltonian approach and energy mapping methods, we determined the exchange interactions, highlighting potential spin frustration in the material. Verification of the mechanical and dynamical stability of CsMn4As3 was conducted, followed by an assessment of its thermoelectric attributes. The observed low lattice thermal conductivity along the c-axis of the compound significantly contributes to a substantial figure of merit (ZT) of 0.8 at 500 K. Leveraging the inherent layered architecture of the material, we modeled a monolayer device and verified its structural integrity through phonon and molecular dynamics analyses. The monolayer exhibited metallic characteristics, prompting an investigation into its I–V response, which uncovered subtle negative differential conductance phenomena. These results underscore the imperative for continued experimental validation to unlock the potential for advanced electronic applications.

  • 2D-THz spectroscopy: exploring the nonlinear dynamics in quantum materials
    Unraveling the nonlinear regime of light–matter interaction in quantum materials at ultrafast timescales has remained elusive over the past few decades. The primary obstacle entailed finding a resonant pump as well as a suitable, resonant probe that could effectively excite and capture the interaction pathways of the collective modes within their inherent timescales. Intriguingly, the characteristic energyscales of the said interactions and the timescales of ensuing dynamics lie in the THz range, making THz radiation not only an apt probe but also an ideal resonant tool for driving the collective modes out of equilibrium. In the said direction, 2D-THz spectroscopy serves as a state-of-the-art technique for unveiling the correlation dynamics of quantum materials through table-top experiments. On a microscopic level, this offers valuable insights into the competing interactions among the charge, spin, lattice, and orbital degrees of freedom. Though the field of 2D-THz spectroscopy is relatively new and yet to be explored in its full potential, this review highlights the progress made in investigating various coupling channels of collective modes, namely magnons, phonons, polaritons, etc in different insulating and semiconducting systems. We also provide pedagogical introduction to the 2D-THz spectroscopy and foresee its emergence alongside cutting-edge experimental tools, reshaping our understanding of quantum materials with new perspectives.

  • Investigating charge transport in a p-Si/n-poly(benzimidazobenzophenanthroline)-BBL thin film heterojunction diode
    The physics of charge transport across the interface in an inorganic Si/organic conducting polymer junction diode has received little attention compared to the inorganic p–n silicon diode. One reason is the amorphous nature of the organic polymer and the polymer chain orientation which introduces disorder and barriers to charge flow. Herein we first present an easy technique to fabricate an inorganic/organic, p-Si/n-poly(benzimidazobenzophenanthroline-BBL) junction diode. The physics of charge transport across the heterojunction, and in the BBL film is then analyzed from the device current-voltage characteristics as a function of temperature in the range 150 K < T < 370 K. The temperature dependence of the diode ideality parameter and of the saturation current density demonstrate that tunneling enhanced charge recombination via exponential trap distributions in the depletion region was responsible for charge transport across the junction. Furthermore, the temperature dependence of the diode conductance revealed that thermal activation and hopping both contributed to charge transport in the BBL film away from the junction. BBL is a ladder polymer with a discrete layered crystal structure that is oriented perpendicular to the substrate. Such polymer chain orientation, combined with a distribution of bond lengths and numerous conjugation paths available for charge delocalization result in the multiple charge transport mechanisms as observed in the diode.