Experimental and theoretical methods of practicing current applied physics, Part I

Abstract

In this special issue, we introduce recent research trends in both experimental and theoretical approaches within the field of applied physics. Apparently, understanding the detailed methods of practicing various investigations is of prime importance in the success of the research. The scope of this issue encompasses sample growth, structural, electronic, and magnetic characterization, as well as first-principles calculations. It provides a comprehensive review and perspective on various experimental and theoretical tools, ranging from basic concepts to state-of-the-art development of the approaches. The advancement of experimental and theoretical methods further advances the field of applied physics, and hence the special issue will serve as an important step in the process. Through this special issue, readers will gain an in-depth understanding of how applied physics is currently being explored in practice.

This issue includes 10 review articles and 5 contributed articles. Articles on sample growth cover topics such as the synthesis of two-dimensional transition metal dichalcogenides (TMDs) on sapphire substrates [1] and the growth of large single crystals using the Czochralski method for quantum materials [2]. Additionally, a novel fabrication method for thin film devices using the focused ion beam, as opposed to traditional solvent methods, is discussed [3]. These contributions provide applied physicists with valuable insights into the synthesis of high-quality materials and solvent-free device fabrication.

In electronic characterization, a method for the visualization and quantification of ionic migration in oxide-based materials (e.g., calcium-doped bismuth ferrite) using electrocoloration has been introduced [4]. This method provides insights into ionic mobility and potential applications for ionic-based devices. Cutting edge of the ARPES technique in condensed matter systems, especially for quantum materials is also presented [5]. The introduction of time-resolved ARPES, nano ARPES, in-situ ARPES, and ARPES with novel control parameters offers a new approach to understanding the electronic structures of quantum and topological materials.

In spectroscopy, the measurement technology for ultrafast magnetism dynamics in magnetic materials is introduced [6]. Terahertz spectral analysis and its applications in materials science, including recent advancements in THz pulse generation and detection methods through high-power lasers and electron accelerators at the fs-THz beamline in the Pohang Accelerator Laboratory is also showcased [7]. Additionally, XPS techniques and methods for accurately analyzing the chemical states of transition metal oxides are presented [8]. These articles will be of great interest to researchers focused on magneto-optics, THz spectroscopy, and XPS.

We also have an article which reviews the advancements in organic liquid scintillator (LS) neutrino detectors, emphasizing the importance of chemical stability and specific optical and physical properties for successful neutrino experiments [9]. Innovations such as environmentally friendly metal-loaded LSs and the use of identical-detector techniques have refined precision measurements of neutrino oscillation parameters. On the other hand, the superconducting properties of a specific high entropy alloy highlights how properties vary with different synthesis methods like arc melting and powder metallurgy and suggested significant implications for practical applications in superconducting magnets [10]. This issue also covers a review on the thermoelectric properties of extrinsic phase mixing in chalcogenide bulk nanocomposites, particularly how structuring at the nanoscale can control thermal conductivity and thermoelectric performance [11].

In a contributed article, DFT approaches on optimizing kesterite materials for photovoltaic applications are reported [12]. The study highlights cost-effective, high-throughput calculations and constructing machine-learning models to estimate the optimal bandgap for solar cell efficiency. This study demonstrates the effective integration of computational physics and machine learning to identify promising materials for solar cell technology. A novel flipping transfer method for van der Waals heterostructures that significantly enhances the cleanliness and performance of fabricated devices is also introduced [13]. This method is expected to greatly advance research in van der Waals heterostructures, offering a simple and efficient approach for device stacking. On the other hand, a protocol for fabricating agar-based tissue-mimicking phantoms to evaluate biomedical optical imaging systems developed [14]. Finally, low-frequency noise behavior in quasi-two-dimensional electron systems within complex oxide heterostructures is introduced [15]. Their findings elucidate the impact of electron distribution and oxygen vacancies on noise characteristics, which has implications for understanding charge trapping and electronic dynamics in oxide-based electronic materials.

In conclusion, each article in this issue contributes significantly to a deeper understanding of materials and devices, encouraging readers to not only absorb this detailed and state-of-the-art knowledge but to also expand upon it. We hope that this issue inspires our readers as much as it fosters the advancement and development of applied physics.