Pub Date : 2026-01-16DOI: 10.1016/j.physb.2026.418298
Aniket Padhy , Praveen Priyaranjan Nayak , S.S. Hota , Om Prakash Das , Ashish Kumar , Guru Prasad Mishra
NaSnFeO4 (NSFO) ceramic is synthesised via the traditional solid-state method to understand the role of structural distortion and defect chemistry. XRD confirmed an orthorhombic NSFO phase. The refined crystallite size and compressive micro-strain reflect noticeable lattice relaxation, while SEM revealed densely packed ∼1 μm grains with uniform elemental distribution. FTIR verified the presence of FeO6 and SnO6 octahedral units, and UV–Vis–NIR spectroscopy established an indirect optical bandgap of 1.95 eV. Dielectric measurements exhibited strong frequency–temperature dispersion and a colossal permittivity of ∼104 (1 kHz, 400 °C), arising from interfacial and defect-assisted polarisation. Jonscher's universal power law governed the AC conductivity, producing activation energies between 0.066 and 0.954 eV. Impedance and modulus analyses confirmed non-Debye relaxation and defect-controlled transport, supported by Nyquist fitting. These findings reveal the interplay between micro-strain, mixed valence, and defect-mediated charge dynamics, demonstrating the potential of NSFO for high-temperature dielectric applications.
{"title":"Defect-mediated relaxation dynamics and mixed-valence coupling in orthorhombic NaSnFeO4 ceramics","authors":"Aniket Padhy , Praveen Priyaranjan Nayak , S.S. Hota , Om Prakash Das , Ashish Kumar , Guru Prasad Mishra","doi":"10.1016/j.physb.2026.418298","DOIUrl":"10.1016/j.physb.2026.418298","url":null,"abstract":"<div><div>NaSnFeO<sub>4</sub> (NSFO) ceramic is synthesised via the traditional solid-state method to understand the role of structural distortion and defect chemistry. XRD confirmed an orthorhombic NSFO phase. The refined crystallite size and compressive micro-strain reflect noticeable lattice relaxation, while SEM revealed densely packed ∼1 μm grains with uniform elemental distribution. FTIR verified the presence of FeO<sub>6</sub> and SnO<sub>6</sub> octahedral units, and UV–Vis–NIR spectroscopy established an indirect optical bandgap of 1.95 eV. Dielectric measurements exhibited strong frequency–temperature dispersion and a colossal permittivity of ∼10<sup>4</sup> (1 kHz, 400 °C), arising from interfacial and defect-assisted polarisation. Jonscher's universal power law governed the AC conductivity, producing activation energies between 0.066 and 0.954 eV. Impedance and modulus analyses confirmed non-Debye relaxation and defect-controlled transport, supported by Nyquist fitting. These findings reveal the interplay between micro-strain, mixed valence, and defect-mediated charge dynamics, demonstrating the potential of NSFO for high-temperature dielectric applications.</div></div>","PeriodicalId":20116,"journal":{"name":"Physica B-condensed Matter","volume":"726 ","pages":"Article 418298"},"PeriodicalIF":2.8,"publicationDate":"2026-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146038250","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-16DOI: 10.1016/j.physb.2026.418291
Ruiyuan Li, Lu Yang, Jianlin He, Zilian Tian
Based on first-principles calculations within the framework of density functional theory (DFT), this work systematically investigates the evolution of geometric structure, electronic properties, and optical characteristics of monolayer GaSe with Se vacancy defects under biaxial tensile and compressive strain, using the Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation. The study reveals a synergistic regulation mechanism between point defects and external strain. Electronic structure analysis indicates that pristine GaSe is an indirect bandgap semiconductor, while the introduction of Se vacancies leads to the emergence of mid-gap states and a reduction in the bandgap. Biaxial strain induces a non-monotonic variation in the bandgap, initially increasing and then decreasing, with the most stable electronic configuration achieved under 4 % compressive strain. Differential charge density analysis demonstrates that strain modulates charge transfer by adjusting interatomic distances and electron cloud distribution, confirming that both tensile and compressive strains significantly influence the electronic structure of the Se-deficient GaSe system. Optical characterizations reveal that Se vacancies reduce both ultraviolet reflectance and absorption, while moderate tensile strain (2 %–6 %) enhances these optical responses. Beyond a critical strain threshold (where UV absorption/reflectance changes from enhancement to suppression), large biaxial strain causes strong lattice distortion and alters Ga–Se bonding around the Se vacancy. This modifies orbital hybridization and shifts/broadens defect states and band edges, narrowing the bandgap and weakening UV optical transitions. Compressive strain not only intensifies the optical response but also induces a shift in the characteristic absorption peaks. This study provides fundamental theoretical insights into the application of GaSe in optoelectronic devices through defect and strain engineering.
{"title":"First-principles study of the coexistence of vacancy and biaxial strain on the photoconductive properties of single-layer GaSe","authors":"Ruiyuan Li, Lu Yang, Jianlin He, Zilian Tian","doi":"10.1016/j.physb.2026.418291","DOIUrl":"10.1016/j.physb.2026.418291","url":null,"abstract":"<div><div>Based on first-principles calculations within the framework of density functional theory (DFT), this work systematically investigates the evolution of geometric structure, electronic properties, and optical characteristics of monolayer GaSe with Se vacancy defects under biaxial tensile and compressive strain, using the Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation. The study reveals a synergistic regulation mechanism between point defects and external strain. Electronic structure analysis indicates that pristine GaSe is an indirect bandgap semiconductor, while the introduction of Se vacancies leads to the emergence of mid-gap states and a reduction in the bandgap. Biaxial strain induces a non-monotonic variation in the bandgap, initially increasing and then decreasing, with the most stable electronic configuration achieved under 4 % compressive strain. Differential charge density analysis demonstrates that strain modulates charge transfer by adjusting interatomic distances and electron cloud distribution, confirming that both tensile and compressive strains significantly influence the electronic structure of the Se-deficient GaSe system. Optical characterizations reveal that Se vacancies reduce both ultraviolet reflectance and absorption, while moderate tensile strain (2 %–6 %) enhances these optical responses. Beyond a critical strain threshold (where UV absorption/reflectance changes from enhancement to suppression), large biaxial strain causes strong lattice distortion and alters Ga–Se bonding around the Se vacancy. This modifies orbital hybridization and shifts/broadens defect states and band edges, narrowing the bandgap and weakening UV optical transitions. Compressive strain not only intensifies the optical response but also induces a shift in the characteristic absorption peaks. This study provides fundamental theoretical insights into the application of GaSe in optoelectronic devices through defect and strain engineering.</div></div>","PeriodicalId":20116,"journal":{"name":"Physica B-condensed Matter","volume":"726 ","pages":"Article 418291"},"PeriodicalIF":2.8,"publicationDate":"2026-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146038249","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-16DOI: 10.1016/j.physb.2026.418290
L.J. Garcia-Angeles , R. Flores-Cruz , M. Arteaga-Varela , C.A. Zamora-Valencia , R. Villafuerte-Segura , V. Rodríguez-Lugo
A theoretical study was conducted using density functional theory (DFT) on the topological insulator Bi2Se3, with the aim of evaluating the effect of substitutional doping at a Bi site with cobalt (Co) and iron (Fe) atoms. Calculations were performed on a pure single-quintuple layer and on two-quintuple-layer systems, one of which was pure and the other doped. The study was carried out using the Vienna Ab initio Simulation Package (VASP), considering spin-orbit coupling (SOC). Optical properties, including the dielectric function, refractive index, and absorption spectra, were also evaluated. These properties showed a clear dependence on both the material thickness and the presence of dopants. It was observed that the inclusion of Co and Fe in the structure can significantly enhance absorption in the IR and visible regions, highlighting the potential for tunable optical response in Bi2Se3-based devices.
{"title":"DFT study of thickness-dependent electronic and optical properties of Bi2Se3 with substitutional doping in single and double quintuple layers","authors":"L.J. Garcia-Angeles , R. Flores-Cruz , M. Arteaga-Varela , C.A. Zamora-Valencia , R. Villafuerte-Segura , V. Rodríguez-Lugo","doi":"10.1016/j.physb.2026.418290","DOIUrl":"10.1016/j.physb.2026.418290","url":null,"abstract":"<div><div>A theoretical study was conducted using density functional theory (DFT) on the topological insulator Bi<sub>2</sub>Se<sub>3</sub>, with the aim of evaluating the effect of substitutional doping at a Bi site with cobalt (Co) and iron (Fe) atoms. Calculations were performed on a pure single-quintuple layer and on two-quintuple-layer systems, one of which was pure and the other doped. The study was carried out using the Vienna Ab initio Simulation Package (VASP), considering spin-orbit coupling (SOC). Optical properties, including the dielectric function, refractive index, and absorption spectra, were also evaluated. These properties showed a clear dependence on both the material thickness and the presence of dopants. It was observed that the inclusion of Co and Fe in the structure can significantly enhance absorption in the IR and visible regions, highlighting the potential for tunable optical response in Bi<sub>2</sub>Se<sub>3</sub>-based devices.</div></div>","PeriodicalId":20116,"journal":{"name":"Physica B-condensed Matter","volume":"726 ","pages":"Article 418290"},"PeriodicalIF":2.8,"publicationDate":"2026-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146038252","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A quaternary derivative of the Pr 1-2-20 system, PrOs2Sn2Zn18, was successfully synthesized in single-crystal form and characterized by X-ray diffraction, specific-heat, electric resistivity and magnetic susceptibility measurements. Unlike the parent compound PrOs2Zn20, which undergoes a structural phase transition at = 87 K, no indication of such a transition was observed in PrOs2Sn2Zn18 down to the lowest temperature of 2 K. The magnetic susceptibility exhibits typical Van Vleck-type temperature-independent paramagnetism below approximately 10 K, suggesting a nonmagnetic crystalline electric field (CEF) ground state. The magnetic specific heat at low temperatures shows a Schottky anomaly centered around 6 K. Analysis based on a two-level model indicates that the CEF ground state is a doublet, with the first excited state being a triplet. These results suggest that the CEF ground state is a non-Kramers doublet. The nature of the non-Kramers ground state and the low-lying CEF excitations of Pr ion are discussed in detail. In addition, the structural stability of PrOs2Sn2Zn18 is examined in comparison with isostructural compounds, Os2Zn20 ( = La, Pr), highlighting the role of Sn substitution in suppressing structural phase transitions.
{"title":"Structural and magnetic properties of a new cubic Pr-based compound PrOs2Sn2Zn18","authors":"Shuto Tamura , Kazuhei Wakiya , Mitsuteru Nakamura , Takanori Taniguchi , Masahito Yoshizawa , Yoshiki Nakanishi","doi":"10.1016/j.physb.2026.418297","DOIUrl":"10.1016/j.physb.2026.418297","url":null,"abstract":"<div><div>A quaternary derivative of the Pr 1-2-20 system, PrOs<sub>2</sub>Sn<sub>2</sub>Zn<sub>18</sub>, was successfully synthesized in single-crystal form and characterized by X-ray diffraction, specific-heat, electric resistivity and magnetic susceptibility measurements. Unlike the parent compound PrOs<sub>2</sub>Zn<sub>20</sub>, which undergoes a structural phase transition at <span><math><msub><mrow><mi>T</mi></mrow><mrow><mi>S</mi></mrow></msub></math></span> = 87 K, no indication of such a transition was observed in PrOs<sub>2</sub>Sn<sub>2</sub>Zn<sub>18</sub> down to the lowest temperature of 2 K. The magnetic susceptibility <span><math><mi>χ</mi></math></span> exhibits typical Van Vleck-type temperature-independent paramagnetism below approximately 10 K, suggesting a nonmagnetic crystalline electric field (CEF) ground state. The magnetic specific heat at low temperatures shows a Schottky anomaly centered around 6 K. Analysis based on a two-level model indicates that the CEF ground state is a doublet, with the first excited state being a triplet. These results suggest that the CEF ground state is a non-Kramers <span><math><msub><mrow><mi>Γ</mi></mrow><mrow><mn>3</mn></mrow></msub></math></span> doublet. The nature of the non-Kramers ground state and the low-lying CEF excitations of Pr<span><math><msup><mrow></mrow><mrow><mn>3</mn><mo>+</mo></mrow></msup></math></span> ion are discussed in detail. In addition, the structural stability of PrOs<sub>2</sub>Sn<sub>2</sub>Zn<sub>18</sub> is examined in comparison with isostructural compounds, <span><math><mi>R</mi></math></span>Os<sub>2</sub>Zn<sub>20</sub> (<span><math><mi>R</mi></math></span> = La, Pr), highlighting the role of Sn substitution in suppressing structural phase transitions.</div></div>","PeriodicalId":20116,"journal":{"name":"Physica B-condensed Matter","volume":"726 ","pages":"Article 418297"},"PeriodicalIF":2.8,"publicationDate":"2026-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146038240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-16DOI: 10.1016/j.physb.2026.418294
Sain Bux Jamali , Zain Ul Abideen , Murad Ali Khaskheli , Muhammad Ilyas Abro , Maheen Malik , Muhammad Akram , Sikandar Ali
Au@Ag nanocuboids were successfully fabricated via symmetric Ag overgrowth on Au-nanorods (NRs) nanocuboids. The seed Au/Ag and AuNRs molar ratios were found to be the same during the synthesis of different-sized core-shell nanocuboids. Adsorption measurements were used to validate the nanocuboids production. The thickness of the core-shell nanorods was systematically adjusted by changing the size of the core particles and the quantity of AgNO3. Using the same concentration of mercaptobenzoic acid (MBA) probe molecules, the core-shell nanocuboids of various sizes that were produced exhibited highly effective surface enhanced Raman spectroscopy (SERS). The nanoparticle size dependent SERS effect was confirmed by the simulation results of electromagnetic (EM) field distribution by finite difference time domain (FDTD) method. The SERS performance was significantly optimized by tuning the excitation laser wavelength from 532 to 638 nm, which allowed the 110 nm and 130 nm nanocuboids to serve as ideal substrates for SERS, thus underscoring their potential for diverse applications.
{"title":"Au@Ag nano cuboids with tunable surface plasmon resonance: A pathway to high-performance and chemically stable SERS substrates","authors":"Sain Bux Jamali , Zain Ul Abideen , Murad Ali Khaskheli , Muhammad Ilyas Abro , Maheen Malik , Muhammad Akram , Sikandar Ali","doi":"10.1016/j.physb.2026.418294","DOIUrl":"10.1016/j.physb.2026.418294","url":null,"abstract":"<div><div>Au@Ag nanocuboids were successfully fabricated <em>via</em> symmetric Ag overgrowth on Au-nanorods (NRs) nanocuboids. The seed Au/Ag and AuNRs molar ratios were found to be the same during the synthesis of different-sized core-shell nanocuboids. Adsorption measurements were used to validate the nanocuboids production. The thickness of the core-shell nanorods was systematically adjusted by changing the size of the core particles and the quantity of AgNO<sub>3</sub>. Using the same concentration of mercaptobenzoic acid (MBA) probe molecules, the core-shell nanocuboids of various sizes that were produced exhibited highly effective surface enhanced Raman spectroscopy (SERS). The nanoparticle size dependent SERS effect was confirmed by the simulation results of electromagnetic (EM) field distribution by finite difference time domain (FDTD) method. The SERS performance was significantly optimized by tuning the excitation laser wavelength from 532 to 638 nm, which allowed the 110 nm and 130 nm nanocuboids to serve as ideal substrates for SERS, thus underscoring their potential for diverse applications.</div></div>","PeriodicalId":20116,"journal":{"name":"Physica B-condensed Matter","volume":"726 ","pages":"Article 418294"},"PeriodicalIF":2.8,"publicationDate":"2026-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146038242","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We have investigated the electronic properties of NaGeAs in its hexagonal crystal structure using first-principles calculations. The electronic band structures were computed both without and with the inclusion of spin–orbit coupling (SOC). A detailed analysis of the SOC-induced band structure reveals a distinct spin splitting near the Fermi level, particularly evident in the valence band, which is attributed to the absence of inversion symmetry in the crystal. This splitting exhibits Rashba-like characteristics, making NaGeAs a promising candidate for spintronic applications. The tunable nature of Rashba-type spin splitting in the valence band of such non-centrosymmetric materials opens avenues for their integration into next-generation spin-based electronic devices.
{"title":"Electronic properties of NaGeAs: First principles calculations","authors":"Varun Tiwari , Shivendra Kumar Gupta , Balwant Singh Arya , Mahendra Aynyas","doi":"10.1016/j.physb.2026.418287","DOIUrl":"10.1016/j.physb.2026.418287","url":null,"abstract":"<div><div>We have investigated the electronic properties of NaGeAs in its hexagonal crystal structure using first-principles calculations. The electronic band structures were computed both without and with the inclusion of spin–orbit coupling (SOC). A detailed analysis of the SOC-induced band structure reveals a distinct spin splitting near the Fermi level, particularly evident in the valence band, which is attributed to the absence of inversion symmetry in the crystal. This splitting exhibits Rashba-like characteristics, making NaGeAs a promising candidate for spintronic applications. The tunable nature of Rashba-type spin splitting in the valence band of such non-centrosymmetric materials opens avenues for their integration into next-generation spin-based electronic devices.</div></div>","PeriodicalId":20116,"journal":{"name":"Physica B-condensed Matter","volume":"727 ","pages":"Article 418287"},"PeriodicalIF":2.8,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146081203","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We present a comprehensive study on the electronic, magnetic, and structural properties of the antiperovskite compound SnNCo3 to investigate its proximity to a ferromagnetic quantum critical point (FM-QCP). Motivated by experimental observations indicating strong electron correlations and spin-glass-like behavior in the absence of long-range magnetic order, we employ density functional theory (DFT) within the local spin density approximation (LSDA), complemented by LSDA+ and fixed spin moment (FSM) methodologies. Surprisingly, our calculations reveal a ferromagnetic ground state with a substantial density of states at the Fermi level, dominated by Co orbitals. The Stoner criteria suggests a magnetic instability in the system, and the ferromagnetic state is energetically favored over antiferromagnetic and nonmagnetic configurations. However, incorporating electron correlations and nitrogen vacancy disorder reveals that strong spin fluctuations significantly renormalize the magnetic energy landscape. Given the absence of long-range magnetic order in the material, we employed the Ginzburg–Landau analysis using FSM calculations, which uncovers soft longitudinal spin fluctuations exceeding the self-consistent Co moment, signaling proximity to ferromagnetic quantum criticality. These findings highlight the subtle interplay of electronic correlations, chemical bonding, and spin fluctuations in driving the magnetism in SnNCo3, and position it as a promising candidate for exploring itinerant ferromagnetic quantum critical behavior in nitride antiperovskites.
{"title":"Effects of non-stoichiometry on the incipient magnetic properties of SnNCo3","authors":"Pragya Tripathi , Himanshu , Murali Rangarajan , J.J. Pulikkotil","doi":"10.1016/j.physb.2026.418293","DOIUrl":"10.1016/j.physb.2026.418293","url":null,"abstract":"<div><div>We present a comprehensive study on the electronic, magnetic, and structural properties of the antiperovskite compound SnNCo<sub>3</sub> to investigate its proximity to a ferromagnetic quantum critical point (FM-QCP). Motivated by experimental observations indicating strong electron correlations and spin-glass-like behavior in the absence of long-range magnetic order, we employ density functional theory (DFT) within the local spin density approximation (LSDA), complemented by LSDA+<span><math><msub><mrow><mi>U</mi></mrow><mrow><mi>e</mi><mi>f</mi><mi>f</mi></mrow></msub></math></span> and fixed spin moment (FSM) methodologies. Surprisingly, our calculations reveal a ferromagnetic ground state with a substantial density of states at the Fermi level, dominated by Co <span><math><mrow><mn>3</mn><mi>d</mi></mrow></math></span> orbitals. The Stoner criteria suggests a magnetic instability in the system, and the ferromagnetic state is energetically favored over antiferromagnetic and nonmagnetic configurations. However, incorporating electron correlations and nitrogen vacancy disorder reveals that strong spin fluctuations significantly renormalize the magnetic energy landscape. Given the absence of long-range magnetic order in the material, we employed the Ginzburg–Landau analysis using FSM calculations, which uncovers soft longitudinal spin fluctuations exceeding the self-consistent Co moment, signaling proximity to ferromagnetic quantum criticality. These findings highlight the subtle interplay of electronic correlations, chemical bonding, and spin fluctuations in driving the magnetism in SnNCo<sub>3</sub>, and position it as a promising candidate for exploring itinerant ferromagnetic quantum critical behavior in nitride antiperovskites.</div></div>","PeriodicalId":20116,"journal":{"name":"Physica B-condensed Matter","volume":"726 ","pages":"Article 418293"},"PeriodicalIF":2.8,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146038254","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
<div><div>Heterogeneous photocatalysis is a semiconductor-based method that converts solar energy into clean chemical energy through water splitting, thus producing green dihydrogen (<span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>), which represents a promising energy carrier. Motivated by the clean nature of the produced energy, the Janus materials ZnSiSSe and ZnSiSeTe have been proposed in this work as potential candidates for water splitting. First-principles calculations based on density functional theory (DFT) were performed to evaluate their performance. The ZnSiSSe and ZnSiSeTe materials are indirect semiconductors, with band gaps calculated using the HSE06 method of 1.28 eV and 1.13 eV, respectively. The ZnSiSSe and ZnSiSeTe structures exhibit significant absorption in the visible range, with absorption coefficients reaching <span><math><mrow><mn>1</mn><mo>.</mo><mn>7</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>5</mn></mrow></msup></mrow></math></span> cm<sup>−1</sup> for ZnSiSSe and <span><math><mrow><mn>3</mn><mo>.</mo><mn>3</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>5</mn></mrow></msup></mrow></math></span> cm<sup>−1</sup> for ZnSiSeTe, extending into the ultraviolet region. The conduction band maximum (CBM) and valence band minimum (VBM) levels appropriately frame the water redox potentials under acidic and neutral conditions and even in a basic medium. Excellent carrier migration affinity is ensured by the effective masses and electron mobility, where the electron effective mass is approximately (<span><math><mrow><mo>≈</mo><mn>2</mn></mrow></math></span> fold) higher than that of holes in ZnSiSSe and (4.3 fold) higher in ZnSiSeTe, with mobilities reaching <span><math><mrow><mn>1</mn><mo>.</mo><mn>09</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>4</mn></mrow></msup></mrow></math></span> cm<span><math><msup><mrow></mrow><mrow><mn>2</mn></mrow></msup></math></span> V<sup>−1</sup> s<sup>−1</sup> and <span><math><mrow><mn>3</mn><mo>.</mo><mn>5</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>4</mn></mrow></msup></mrow></math></span> cm<span><math><msup><mrow></mrow><mrow><mn>2</mn></mrow></msup></math></span> V<sup>−1</sup> s<sup>−1</sup>, respectively, surpassing several systematically studied materials. The hydrogen conversion efficiency (STH) of ZnSiSSe (24.89%) and ZnSiSeTe (26.89%) significantly exceeds the theoretical value (18%) for <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> production, surpassing that of several materials. The structures also show excellent solar-to-hydrogen (STH) conversion efficiency under compressive strain. Under a -5% strain, the STH reaches (30.4%) for ZnSiSSe and (30.2%) for ZnSiSeTe. The free energy calculation indicates that the structures ZnSiSSe and ZnSiSeTe exhibit high performance under light irradiation for activating the hydrogen evolution reaction (
{"title":"Synergistic optimization of optical and electronic properties in Janus ZnSiSSe and ZnSiSeTe for solar-driven hydrogen evolution","authors":"Abdelmajid Es-saadi , Zakaryae Haman , Moussa Kibbou , Lahcen Aznague , El-m’feddal Adadi , Ismail Essaoudi , Abdelmajid Ainane","doi":"10.1016/j.physb.2026.418292","DOIUrl":"10.1016/j.physb.2026.418292","url":null,"abstract":"<div><div>Heterogeneous photocatalysis is a semiconductor-based method that converts solar energy into clean chemical energy through water splitting, thus producing green dihydrogen (<span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>), which represents a promising energy carrier. Motivated by the clean nature of the produced energy, the Janus materials ZnSiSSe and ZnSiSeTe have been proposed in this work as potential candidates for water splitting. First-principles calculations based on density functional theory (DFT) were performed to evaluate their performance. The ZnSiSSe and ZnSiSeTe materials are indirect semiconductors, with band gaps calculated using the HSE06 method of 1.28 eV and 1.13 eV, respectively. The ZnSiSSe and ZnSiSeTe structures exhibit significant absorption in the visible range, with absorption coefficients reaching <span><math><mrow><mn>1</mn><mo>.</mo><mn>7</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>5</mn></mrow></msup></mrow></math></span> cm<sup>−1</sup> for ZnSiSSe and <span><math><mrow><mn>3</mn><mo>.</mo><mn>3</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>5</mn></mrow></msup></mrow></math></span> cm<sup>−1</sup> for ZnSiSeTe, extending into the ultraviolet region. The conduction band maximum (CBM) and valence band minimum (VBM) levels appropriately frame the water redox potentials under acidic and neutral conditions and even in a basic medium. Excellent carrier migration affinity is ensured by the effective masses and electron mobility, where the electron effective mass is approximately (<span><math><mrow><mo>≈</mo><mn>2</mn></mrow></math></span> fold) higher than that of holes in ZnSiSSe and (4.3 fold) higher in ZnSiSeTe, with mobilities reaching <span><math><mrow><mn>1</mn><mo>.</mo><mn>09</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>4</mn></mrow></msup></mrow></math></span> cm<span><math><msup><mrow></mrow><mrow><mn>2</mn></mrow></msup></math></span> V<sup>−1</sup> s<sup>−1</sup> and <span><math><mrow><mn>3</mn><mo>.</mo><mn>5</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>4</mn></mrow></msup></mrow></math></span> cm<span><math><msup><mrow></mrow><mrow><mn>2</mn></mrow></msup></math></span> V<sup>−1</sup> s<sup>−1</sup>, respectively, surpassing several systematically studied materials. The hydrogen conversion efficiency (STH) of ZnSiSSe (24.89%) and ZnSiSeTe (26.89%) significantly exceeds the theoretical value (18%) for <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> production, surpassing that of several materials. The structures also show excellent solar-to-hydrogen (STH) conversion efficiency under compressive strain. Under a -5% strain, the STH reaches (30.4%) for ZnSiSSe and (30.2%) for ZnSiSeTe. The free energy calculation indicates that the structures ZnSiSSe and ZnSiSeTe exhibit high performance under light irradiation for activating the hydrogen evolution reaction (","PeriodicalId":20116,"journal":{"name":"Physica B-condensed Matter","volume":"726 ","pages":"Article 418292"},"PeriodicalIF":2.8,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146038255","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-15DOI: 10.1016/j.physb.2026.418289
Aitijhya Saha , Debraj Rakshit
In this work, we consider a non-Hermitian system described via a one-dimensional single-particle tight-binding model, where the non-Hermiticity is governed by random nearest-neighbour tunnellings, such that the left-to-right and right-to-left hopping strengths are unequal. A physical situation of a completely real eigenspectrum arises owing to the Hamiltonian’s tridiagonal matrix structure under a simple sign conservation of the product of the conjugate nearest-neighbour tunnelling terms. The off-diagonal disorder leads the non-Hermitian system to a delocalization–localization crossover in finite systems. The emergent nature of the crossover is recognized through a finite-size spectral analysis. The system enters into a localized phase for infinitesimal disorder strength in the thermodynamic limit. We perform a careful scaling analysis of localization length, inverse participation ratio (IPR), and energy splitting and report the corresponding scaling exponents. Noticeably, in contrast to the diagonal disorder, the density of states (DOS) has a singularity at in the presence of the off-diagonal disorder, and the corresponding wavefunction remains delocalized for any given disorder strength.
{"title":"Localization with non-Hermitian off-diagonal disorder","authors":"Aitijhya Saha , Debraj Rakshit","doi":"10.1016/j.physb.2026.418289","DOIUrl":"10.1016/j.physb.2026.418289","url":null,"abstract":"<div><div>In this work, we consider a non-Hermitian system described via a one-dimensional single-particle tight-binding model, where the non-Hermiticity is governed by random nearest-neighbour tunnellings, such that the left-to-right and right-to-left hopping strengths are unequal. A physical situation of a completely real eigenspectrum arises owing to the Hamiltonian’s tridiagonal matrix structure under a simple <em>sign conservation</em> of the product of the conjugate nearest-neighbour tunnelling terms. The off-diagonal disorder leads the non-Hermitian system to a delocalization–localization crossover in finite systems. The emergent nature of the crossover is recognized through a finite-size spectral analysis. The system enters into a localized phase for infinitesimal disorder strength in the thermodynamic limit. We perform a careful scaling analysis of localization length, inverse participation ratio (IPR), and energy splitting and report the corresponding scaling exponents. Noticeably, in contrast to the diagonal disorder, the density of states (DOS) has a singularity at <span><math><mrow><mi>E</mi><mo>=</mo><mn>0</mn></mrow></math></span> in the presence of the off-diagonal disorder, and the corresponding wavefunction remains delocalized for any given disorder strength.</div></div>","PeriodicalId":20116,"journal":{"name":"Physica B-condensed Matter","volume":"726 ","pages":"Article 418289"},"PeriodicalIF":2.8,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145978741","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We report on the observation on proximity-induced superconductivity in the topological insulator BiSbTeSe2 coupled to a disordered superconductor, amorphous indium oxide (a-InO). Resistance-temperature measurements reveal superconducting signatures at low temperatures, even when InO is in an insulating state, indicating the persistence of superconducting correlations. Differential conductance measurements exhibit a prominent zero-bias conductance peak, along with multiple peaks at higher biases, suggestive of multiple Andreev reflections. Above 10 K, the zero-bias peak and conductance oscillations vanish, marking the critical temperature (T∗) of the superconducting islands in InO. These results underscore the influence of topological surface states on proximity-induced superconductivity and highlight the role of superconducting fluctuations in disordered superconductor/topological-insulator hybrid interfaces.
{"title":"Conductance oscillations in a topological insulator–disordered superconductor hybrid interface","authors":"Jagadis Prasad Nayak , Aviad Frydman , Gopi Nath Daptary","doi":"10.1016/j.physb.2026.418248","DOIUrl":"10.1016/j.physb.2026.418248","url":null,"abstract":"<div><div>We report on the observation on proximity-induced superconductivity in the topological insulator BiSbTeSe<sub>2</sub> coupled to a disordered superconductor, amorphous indium oxide (a-InO). Resistance-temperature measurements reveal superconducting signatures at low temperatures, even when InO is in an insulating state, indicating the persistence of superconducting correlations. Differential conductance measurements exhibit a prominent zero-bias conductance peak, along with multiple peaks at higher biases, suggestive of multiple Andreev reflections. Above 10 K, the zero-bias peak and conductance oscillations vanish, marking the critical temperature (T∗) of the superconducting islands in InO. These results underscore the influence of topological surface states on proximity-induced superconductivity and highlight the role of superconducting fluctuations in disordered superconductor/topological-insulator hybrid interfaces.</div></div>","PeriodicalId":20116,"journal":{"name":"Physica B-condensed Matter","volume":"726 ","pages":"Article 418248"},"PeriodicalIF":2.8,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145978739","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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