Article
Nanoscience & Nanotechnology
Leonarde N. Rodrigues, Diego Scolfaro, Lucas da Conceicao, Angelo Malachias, Odilon D. D. Couto, Fernando Iikawa, Christoph Deneke
Summary: Strain-based band structure engineering is shown to be an effective tool for tuning the optical and electronic properties of semiconductor nanostructures. By integrating InGaAs quantum wells into rolled-up heterostructures and changing their geometrical configuration, the band structure is tunable and the emitted light can have modified helicity. Experimental results demonstrate significant energy shifts and inversions of band states in rolled-up structures compared to flat structures, leading to changes in the optical selection rules and vanishing spin polarization. Comparisons between experiment and theory show excellent agreement, suggesting potential applications in developing novel optical devices for quantum information technology.
ACS APPLIED NANO MATERIALS
(2021)
Article
Chemistry, Physical
Mehdi Khosravi, Hadi Feizi, Behzad Haghighi, Suleyman Allakhverdiev, Mohammad Mahdi Najafpour
Summary: Photocatalysts are important for green fuel production. The study compared the photo-electrochemical performance and behavior of mixed-phase titanium oxide and iron oxide heterojunction with titanium oxide nanotubes and iron oxide heterojunction. Results showed that factors such as stabilization potential and dissolved oxygen did not significantly affect the photo-electrochemical properties of the electrodes.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2021)
Article
Chemistry, Inorganic & Nuclear
Alisher F. Murtazoev, Sergey G. Dorofeev, Alexey O. Gudovannyy, Konstantin A. Lyssenko, Valery A. Dolgikh, Peter S. Berdonosov
Summary: New europium selenate tetrahydrate Eu2(SeO4)3.4H2O was successfully prepared by hydrothermal technique, and its crystal structure was determined. The compound has a similar structure to other selenates and exhibits good spectroscopic properties. It shows high stability in thermal analysis.
JOURNAL OF SOLID STATE CHEMISTRY
(2022)
Article
Physics, Applied
Maciej P. Polak, Pawel Scharoch, Robert Kudrawiec
Summary: The band gap engineering of group IV semiconductors, particularly in alloys such as GeSn, has received attention for its potential applications in light emitters. This study investigates the electronic band structure of various group IV semiconductor alloys, revealing changes in the band structure and the potential for direct band gaps. The results suggest that alloying Si and Ge with other group IV elements could enhance the functionality of group IV semiconductors.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2021)
Article
Chemistry, Multidisciplinary
Yali Yu, Tao Xiong, Yue-Yang Liu, Juehan Yang, Jian-Bai Xia, Zhongming Wei
Summary: Polarization imaging has advantages in capturing spatial, spectral, and polarization information across various spectral bands. This study systematically elucidates the characteristics of anisotropic absorption reversal in pucker-like group IV-VI semiconductors MX (M = Ge, Sn; X = S, Se) and explores the fundamental mechanisms behind anisotropy reversal in different bands. The results indicate that utilizing polarization reversal photodetectors holds advantages in achieving multifunctional integration within the device structure while simplifying its configuration, including band information identification and image enhancement.
ADVANCED MATERIALS
(2023)
Article
Chemistry, Physical
Miao Liu, Chuan-Lu Yang, Mei-Shan Wang, Xiao-Guang Ma
Summary: The photocatalytic hydrogen evolution reaction by antimonene nanoribbon with halogen edge passivation shows enhanced performance under tensile strain larger than 4%, and the different halogen edges have varying effects on the electronic properties. The nanoribbons with hydrogen edge passivation exhibit valence band and conduction band maximums matching the redox potentials for water-splitting HER, indicating their potential as preferable candidates for solar light photocatalytic water splitting for hydrogen production.
JOURNAL OF PHYSICAL CHEMISTRY C
(2021)
Article
Engineering, Electrical & Electronic
Sai Kiran Ayyala, James A. Covington
Summary: In this study, a VOC sensor based on metal oxide was developed using ZnO/MoO3 heterojunction thick film devices. These devices can detect various VOCs at ppb concentrations relevant to applications, showing higher sensitivity and shorter response time.
IEEE SENSORS JOURNAL
(2022)
Article
Physics, Multidisciplinary
Chaoxin Huang, Benyuan Cheng, Yunwei Zhang, Long Jiang, Lisi Li, Mengwu Huo, Hui Liu, Xing Huang, Feixiang Liang, Lan Chen, Hualei Sun, Meng Wang
Summary: We synthesized and characterized a Si-based ternary semiconductor Mg3Si2Te6, which has a quasi-two-dimensional structure with trigonal Mg2Si2Te6 layers separated by Mg ions. Ultraviolet-visible absorption spectroscopy and density functional theory calculations were used to investigate its electronic structure. The experimentally determined direct band gap of 1.39 eV matches well with the calculated value. Our findings suggest that Mg3Si2Te6 is a direct gap semiconductor and a potential candidate for near-infrared optoelectronic devices.
Article
Engineering, Electrical & Electronic
Ioannis E. Fragkos, Wei Sun, Damir Borovac, Renbo Song, Jonathan J. Wierer, Nelson Tansu
Summary: This study investigates an active region design based on InGaN / delta-InN quantum well (QW) for potential high-efficiency visible light emitters. The results demonstrate a large wavelength redshift and an increase in the electron-hole wavefunction overlap for the delta-structure compared to the conventional InGaN QW.
IEEE JOURNAL OF QUANTUM ELECTRONICS
(2022)
Article
Chemistry, Multidisciplinary
Hirokazu Narita, Motoki Maeda, Chiharu Tokoro, Tomoya Suzuki, Mikiya Tanaka, Hideaki Shiwaku, Tsuyoshi Yaita
Summary: In this study, the mechanism of Se(iv) and Se(vi) extraction from aqueous HCl solutions by EHBAA was investigated. The extraction behavior and structural properties of the dominant Se species in solution were examined. It was found that Se(vi) was reduced to Se(iv) in 8 M HCl, and around 50% of Se(vi) was extracted from 0.5 M HCl using 0.5 M EHBAA. On the other hand, Se(iv) was hardly extracted from 0.5 to 5 M HCl, but the extraction efficiency increased drastically above 5 M, reaching approximately 85%. The apparent stoichiometries of Se(iv) or Se(vi) to EHBAA were 1:1 and 1:2, respectively.
Article
Materials Science, Multidisciplinary
Yu. V. Verbovytskyy
Summary: Phase equilibria in the Eu-Zn-Ga ternary system were established at 400 degrees C within the range of europium concentrations 0-33.3 at.%. The phases and crystal structures of the analyzed materials were identified using X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The system exhibited the formation of four solid solutions and a ternary intermetallic compound, as well as one continuous solid solution and eight ternary phase fields at 400 degrees C.
Article
Chemistry, Physical
Meryem Ziati, Hamid Ez-Zahraouy
Summary: The effects of fluorine substitution and uniaxial strain on the structural, electronic, and optical properties of the superconductor Sr2RuO4 were investigated. Fluorine substitution was found to open the band gap and results in an indirect semiconductor material Sr2RuO4-xFx. The electronic properties of Sr2RuO2F2 can be tuned under external pressure, and the absorption ability is improved as well.
Article
Materials Science, Multidisciplinary
Dmitry Skachkov, Shuang-Long Liu, Yan Wang, Xiao-Guang Zhang, Hai-Ping Cheng
Summary: The study presents a first-principles theory for Schottky barrier physics, utilizing density functional theory to compute the Schottky barrier including thousands of atomic layers in the semiconductor. Self-consistent solutions of the Poisson equation provide induced charge and electrostatic potential, leading to the determination of Schottky barrier height. Tests on GaAs-graphene and Si/Al heterostructures demonstrate the self-consistent determination of SBH, width, and depletion and inversion layers as functions of temperature and bulk doping.
Article
Chemistry, Multidisciplinary
Huatian Shi, Hung Kay Lee, Yi Pan, Kai-Chung Lau, Shek-Man Yiu, William W. Y. Lam, Wai-Lun Man, Tai-Chu Lau
Summary: This study presents the isolation and X-ray structure of a rare Mn(VI) nitrido complex, which exhibits N atom transfer reactions and catalytic abilities with NADH analogues.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2021)
Review
Materials Science, Multidisciplinary
Jiangang He, Karin M. Rabe, Chris Wolverton
Summary: This article presents the crystal and electronic structures of Heusler compounds and its derivatives, as well as the state-of-the-art computational methods for materials discovery. It highlights the recent achievements in computational materials discoveries of Heusler compounds with promising applications in various fields. The article concludes with prospects for accelerated Heusler materials discovery and the challenges in predicting properties.
Article
Physics, Condensed Matter
Oliver Rader, Jaime Sanchez-Barriga, Emile D. L. Rienks, Andrei Varykhalov, Gunther Springholz, Lada V. Yashina
Summary: This paper reviews the search for magnetic bandgap in topological materials and demonstrates the opening of a magnetic bandgap in the topological insulator heterostructure MnBi2Te4/Bi2Te3. It discusses the reasons for nonmagnetic gaps when Se replaces Te, introduces the use of ARPES to probe the quantum final state, and highlights the importance of studying spin texture in topological states.
PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS
(2021)
Article
Chemistry, Multidisciplinary
Rafal Rechcinski, Marta Galicka, Mathias Simma, Valentine V. Volobuev, Ondrej Caha, Jaime Sanchez-Barriga, Partha S. Mandal, Evangelos Golias, Andrei Varykhalov, Oliver Rader, Guenther Bauer, Perla Kacman, Ryszard Buczko, Gunther Springholz
Summary: Structure inversion asymmetry is an inherent feature of quantum confined heterostructures with non-equivalent interfaces, leading to spin splitting of electron states and strong effects on electronic band structure, particularly prominent in topological insulators. The effect can be controlled and enhanced by modifying the surface conditions, affecting the spin splitting decisively depending on hybridization and quantum well width. The findings open up new possibilities for tuning such systems for device applications.
ADVANCED FUNCTIONAL MATERIALS
(2021)
Article
Physics, Multidisciplinary
Juraj Krempasky, Laurent Nicolai, Martin Gmitra, Houke Chen, Mauro Fanciulli, Eduardo B. Guedes, Marco Caputo, Milan Radovic, Valentine V. Volobuev, Ondrej Caha, Gunther Springholz, Jan Minar, J. Hugo Dil
Summary: The study reveals that ferroelectric alpha-GeTe exhibits a multiple nontrivial topology of the electronic band structure, with the presence of triple-points and type-II Weyl fermions. Using spin- and angle-resolved photoemission spectroscopy combined with density functional theory, the research uncovers the unique spin texture around the triple point caused by the crossing of spin-degenerate and spin-split bands.
PHYSICAL REVIEW LETTERS
(2021)
Article
Chemistry, Multidisciplinary
Stefan Wimmer, Jaime Sanchez-Barriga, Philipp Kueppers, Andreas Ney, Enrico Schierle, Friedrich Freyse, Ondrej Caha, Jan Michalicka, Marcus Liebmann, Daniel Primetzhofer, Martin Hoffman, Arthur Ernst, Mikhail M. Otrokov, Gustav Bihlmayer, Eugen Weschke, Bella Lake, Evgueni V. Chulkov, Markus Morgenstern, Guenther Bauer, Gunther Springholz, Oliver Rader
Summary: This study demonstrates that p-type MnSb2Te4, previously considered topologically trivial, can become a ferromagnetic topological insulator with a few percent Mn excess, showing record Curie temperature and out-of-plane magnetic anisotropy. Experimental results reveal phenomena such as ferromagnetic hysteresis, a 2D Dirac cone, out-of-plane spin polarization, and bandgap closing at the Curie temperature.
ADVANCED MATERIALS
(2021)
Article
Chemistry, Multidisciplinary
Oliver J. Clark, Indrajit Wadgaonkar, Friedrich Freyse, Gunther Springholz, Marco Battiato, Jaime Sanchez-Barriga
Summary: The dynamics of ferroelectric Rashba semiconductors after optical excitation have been studied experimentally, revealing unconventional temperature dependence attributed to the interdependence of electron-electron and electron-phonon interactions. The findings are supported by theoretical calculations using the Boltzmann approach.
ADVANCED MATERIALS
(2022)
Editorial Material
Materials Science, Multidisciplinary
Moritz Brehm, Gunther Springholz
PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE
(2022)
Article
Multidisciplinary Sciences
Geoffroy Kremer, Julian Maklar, Laurent Nicolai, Christopher W. Nicholson, Changming Yue, Caio Silva, Philipp Werner, J. Hugo Dil, Juraj Krempasky, Gunther Springholz, Ralph Ernstorfer, Jan Minar, Laurenz Rettig, Claude Monney
Summary: α-GeTe(111) is a non-centrosymmetric ferroelectric semiconductor material with a strong spin-orbit interaction and giant Rashba coupling. Its ferroelectric polarization can be controlled by an electric field at room temperature, and research shows that femtosecond light pulses can modulate the Rashba coupling and enhance the lattice distortion on a femtosecond timescale.
NATURE COMMUNICATIONS
(2022)
Article
Physics, Multidisciplinary
R. D. Gonzalez Betancourt, J. Zubac, R. Gonzalez-Hernandez, K. Geishendorf, Z. Soban, G. Springholz, K. Olejnik, L. Smejkal, J. Sinova, T. Jungwirth, S. T. B. Goennenwein, A. Thomas, H. Reichlova, J. Zelezny, D. Kriegner
Summary: A spontaneous anomalous Hall signal was observed in an epitaxial film of MnTe, a semiconductor with collinear antiparallel magnetic ordering and zero net magnetization, even in the absence of an external magnetic field. The anomalous Hall effect originates from the unconventional phase with strong time-reversal symmetry breaking and alternating spin polarization. The anisotropic crystal environment of Mn atoms, caused by nonmagnetic Te atoms, plays a vital role in establishing the unconventional phase and generating the anomalous Hall effect.
PHYSICAL REVIEW LETTERS
(2023)
Article
Materials Science, Multidisciplinary
Changqing Zhu, Patrick Pilch, Anneke Reinold, Dennis Kudlacik, Gunther Springholz, Alberta Bonanni, Marc Assmann, Mirko Cinchetti, Zhe Wang
Summary: We present a study on the time-resolved optical and terahertz ultrafast spectroscopy of charge-carrier dynamics in the room-temperature antiferromagnetic semiconductor alpha-MnTe. By optically pumping the system with 1.55 eV photons at room temperature, charge carriers are excited in the conduction band and their dynamical response in the nonequilibrium states is investigated using optical and terahertz transmission probes. Three relaxation processes with characteristic relaxation times of approximately 1, 10, and 100 ps are identified, and their exact values depend on the pump fluence. Nonlinear dependence on the pump fluence is observed in both the optical and terahertz probes at high pump fluences.
PHYSICAL REVIEW MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
J. Bermejo-Ortiz, G. Krizman, R. Jakiela, Z. Khosravizadeh, M. Hajlaoui, G. Bauer, G. Springholz, L. -A. de Vaulchier, Y. Guldner
Summary: On smooth interfaces between a trivial and a topological material, massless Weyl and massive Dirac fermions coexist, with their energy spectra controlled by the smoothness of the topological interface. The optical absorption of the zero-energy chiral Weyl state is also affected by the smoothness of the interface.
Article
Materials Science, Multidisciplinary
S. C. P. van Kooten, G. Springholz, A. B. Henriques
Summary: The study elucidated the spin dynamics involved in the birth and growth of giant spin polarons in a magnetic semiconductor and proposed a new measurement technique. Experimental data and numerical simulations indicated that temperature and fluctuations in the Weiss field play a crucial role in spin coherence generation.
Article
Physics, Multidisciplinary
G. Krizman, B. A. Assaf, M. Orlita, G. Bauer, G. Springholz, R. Ferreira, L. A. de Vaulchier, Y. Guldner
Summary: Topological interface states in multivalley systems are studied using magnetooptical Landau level spectroscopy in topological crystalline insulator heterostructures. The properties of these states are characterized, revealing the factors affecting them in two dimensions.
PHYSICAL REVIEW RESEARCH
(2022)
Article
Materials Science, Multidisciplinary
D. Bossini, S. Dal Conte, M. Terschanski, G. Springholz, A. Bonanni, K. Deltenre, F. Anders, G. S. Uhrig, G. Cerullo, M. Cinchetti
Summary: Spintronics aims to utilize the magnetic degree of freedom of electrons for computation and couple it to charges, with the potential to use antiferromagnets for high frequency spin manipulations in combination with the tunable electronic properties of semiconductors. The study in this paper demonstrates that phonon modes can modulate both the charge and magnetic degree of freedom, suggesting a resonant pumping of phonons as a viable way to link spin and charge dynamics even in nonlinear regimes. Experimental observations align with theoretical predictions, showing coherent and incoherent responses to photoinduced THz spin dynamics.
Article
Materials Science, Multidisciplinary
Alexander Kazakov, Wojciech Brzezicki, Timo Hyart, Bartlomiej Turowski, Jakub Polaczynski, Zbigniew Adamus, Marta Aleszkiewicz, Tomasz Wojciechowski, Jaroslaw Z. Domagala, Ondrej Caha, Andrei Varykhalov, Gunther Springholz, Tomasz Wojtowicz, Valentine V. Volobuev, Tomasz Dietl
Summary: The research investigates the saturation of coherence length in conductors, such as Dirac materials, at decreasing temperatures, attributing this phenomenon to external noise, residual magnetic impurities, or two-level systems specific to noncrystalline solids. Theoretical analysis and experimental studies on the SnTe-class compounds reveal the deteriorating effect of breaking mirror symmetry on Berry's phase quantization and weak-antilocalization magnetoresistance. The results suggest that spatial symmetries should also be considered in classifying quantum transport phenomena.
Article
Materials Science, Multidisciplinary
G. Krizman, B. A. Assaf, G. Bauer, G. Springholz, L. A. de Vaulchier, Y. Guldner
Summary: Periodic stacking of topologically trivial and nontrivial layers with opposite symmetry of the valence and conduction bands can induce topological interface states, leading to the emergence of tunable topological minibands. These minibands exhibit topological characteristics confirmed by magnetooptical spectroscopy, with temperature-dependent topological phase transitions observed within the minibands. The critical temperature, miniband gap, and miniband width can be precisely controlled by layer thicknesses and compositions, providing a template for the realization of magnetic Weyl semimetals and other strongly interacting topological phases.
