Pub Date : 2025-12-01DOI: 10.1016/j.mtquan.2025.100058
Juhi Singh, Narayan Mohanta
We propose an altermagnet–topological insulator bilayer as a platform to engineer Berry phase driven spin–charge responses using an interfacial buffer layer. Using a momentum-space lattice model and linear-response theory, we investigate a -wave altermagnet coupled to a topological insulator and highlight the crucial role of spin-flip tunneling in shaping its electronic and transport properties. Interfacial hybridization strongly modifies the band structure, leading to anisotropic Rashba–Edelstein and Hall responses. The spin-flip component of the coupling induces an inverse -wave spin texture in the altermagnetic bands, signaling the onset of an altermagnetic topological phase. This coupling also renders the Rashba–Edelstein effect strongly in-plane anisotropic, enhancing the transverse response relative to ferromagnetic or antiferromagnetic analogues. These results establish interfacial spin-flip tunneling as a practical control knob for direction-sensitive, stray-field–free spin–charge conversion in correlated topological heterostructures.
{"title":"Interface controlled Berry phase and anisotropic spin–charge conversion in altermagnet–topological insulator bilayers","authors":"Juhi Singh, Narayan Mohanta","doi":"10.1016/j.mtquan.2025.100058","DOIUrl":"10.1016/j.mtquan.2025.100058","url":null,"abstract":"<div><div>We propose an altermagnet–topological insulator bilayer as a platform to engineer Berry phase driven spin–charge responses using an interfacial buffer layer. Using a momentum-space lattice model and linear-response theory, we investigate a <span><math><mi>d</mi></math></span>-wave altermagnet coupled to a topological insulator and highlight the crucial role of spin-flip tunneling in shaping its electronic and transport properties. Interfacial hybridization strongly modifies the band structure, leading to anisotropic Rashba–Edelstein and Hall responses. The spin-flip component of the coupling induces an inverse <span><math><mi>d</mi></math></span>-wave spin texture in the altermagnetic bands, signaling the onset of an altermagnetic topological phase. This coupling also renders the Rashba–Edelstein effect strongly in-plane anisotropic, enhancing the transverse response relative to ferromagnetic or antiferromagnetic analogues. These results establish interfacial spin-flip tunneling as a practical control knob for direction-sensitive, stray-field–free spin–charge conversion in correlated topological heterostructures.</div></div>","PeriodicalId":100894,"journal":{"name":"Materials Today Quantum","volume":"8 ","pages":"Article 100058"},"PeriodicalIF":0.0,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145684135","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-23DOI: 10.1016/j.mtquan.2025.100057
Po-Yao Chang
Topological nodal-line semimetals (NLSMs) are a new family of topological materials characterized by electronic band crossings that form lines in the Brillouin zone. These NLSMs host exotic nodal-line structures and exhibit distinct features such as drumhead surface states and unique electromagnetic responses. This review classifies various NLSM types based on their nodal structures and protecting symmetries, highlighting that these nodal-line structures can form links, knots, and chains. We discuss their characteristic electromagnetic responses, including Landau level spectroscopy, optical conductivity, and permittivity. Furthermore, the strong correlation effects in these NLSMs modify their semimetallic phases and lead to novel quantum phases where magnetism and superconductivity intertwine.
{"title":"Nodal-line semimetals and their variance","authors":"Po-Yao Chang","doi":"10.1016/j.mtquan.2025.100057","DOIUrl":"10.1016/j.mtquan.2025.100057","url":null,"abstract":"<div><div>Topological nodal-line semimetals (NLSMs) are a new family of topological materials characterized by electronic band crossings that form lines in the Brillouin zone. These NLSMs host exotic nodal-line structures and exhibit distinct features such as drumhead surface states and unique electromagnetic responses. This review classifies various NLSM types based on their nodal structures and protecting symmetries, highlighting that these nodal-line structures can form links, knots, and chains. We discuss their characteristic electromagnetic responses, including Landau level spectroscopy, optical conductivity, and permittivity. Furthermore, the strong correlation effects in these NLSMs modify their semimetallic phases and lead to novel quantum phases where magnetism and superconductivity intertwine.</div></div>","PeriodicalId":100894,"journal":{"name":"Materials Today Quantum","volume":"8 ","pages":"Article 100057"},"PeriodicalIF":0.0,"publicationDate":"2025-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145364167","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-16DOI: 10.1016/j.mtquan.2025.100056
Houhao Wang , Sergey Y. Savrasov , Xiangang Wan , Feng Tang
Topological band crossings (BCs) such as Dirac and Weyl points can provide intriguing physical properties in both fermionic systems and bosonic systems, like surface Fermi arcs, chiral anomaly, spin-momentum locking, and among others. Unlike BCs at high-symmetry points (HSPs) formed by a single degenerate irreducible representation (irrep), those in high-symmetry lines (HSLs) are degeneracies formed by two different irreps. For fermionic systems, such BCs near the Fermi level can be effectively diagnosed using symmetry data at HSPs, namely, the number of times each irrep of occupied bands occurs at HSPs. For phonon systems, phonon BCs in the entire frequency window are meaningful. Here, we propose a new diagnostic scheme for detecting phonon BCs by compatibility relations (CRs), which would otherwise be invisible to traditional methods as applied in electronic bands. Based on 230 space groups, we apply our diagnostic scheme to the Phonon Database at Kyoto University (consisting of 10,034 materials) and identify 2,815,357 emergent particles (EMPs) in HSLs. These EMPs include C-1 WP, C-2 DP, C-2 WP, C-3 WP, DP, P-WNL, P-WNLs, QDP, QTP, and TP, providing a platform to assist experimentalists in exploring the practical application value of phonon EMPs. Our diagnostic scheme can also be applied to other bosonic systems like photon and magnon systems and extended to other symmetries, such as magnetic space groups and spin space groups.
{"title":"Diagnosis of enforced phonon band crossings in the entire frequency window by compatibility relations","authors":"Houhao Wang , Sergey Y. Savrasov , Xiangang Wan , Feng Tang","doi":"10.1016/j.mtquan.2025.100056","DOIUrl":"10.1016/j.mtquan.2025.100056","url":null,"abstract":"<div><div>Topological band crossings (BCs) such as Dirac and Weyl points can provide intriguing physical properties in both fermionic systems and bosonic systems, like surface Fermi arcs, chiral anomaly, spin-momentum locking, and among others. Unlike BCs at high-symmetry points (HSPs) formed by a single degenerate irreducible representation (irrep), those in high-symmetry lines (HSLs) are degeneracies formed by two different irreps. For fermionic systems, such BCs near the Fermi level can be effectively diagnosed using symmetry data at HSPs, namely, the number of times each irrep of occupied bands occurs at HSPs. For phonon systems, phonon BCs in the entire frequency window are meaningful. Here, we propose a new diagnostic scheme for detecting phonon BCs by compatibility relations (CRs), which would otherwise be invisible to traditional methods as applied in electronic bands. Based on 230 space groups, we apply our diagnostic scheme to the Phonon Database at Kyoto University (consisting of 10,034 materials) and identify 2,815,357 emergent particles (EMPs) in HSLs. These EMPs include C-1 WP, C-2 DP, C-2 WP, C-3 WP, DP, P-WNL, P-WNLs, QDP, QTP, and TP, providing a platform to assist experimentalists in exploring the practical application value of phonon EMPs. Our diagnostic scheme can also be applied to other bosonic systems like photon and magnon systems and extended to other symmetries, such as magnetic space groups and spin space groups.</div></div>","PeriodicalId":100894,"journal":{"name":"Materials Today Quantum","volume":"8 ","pages":"Article 100056"},"PeriodicalIF":0.0,"publicationDate":"2025-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145364168","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Three-dimensional topological semimetals hosting Dirac or Weyl fermions are a new kind of materials class in which conduction and valence bands cross each other. Such materials harbor a nontrivial Berry phase, which is an additional geometrical phase factor arising along the path of an adiabatic surface and can give rise to experimentally measurable quantities such as an anomalous Hall component. Here we report a systematic study of quantum oscillations of thermoelectric power in single crystals of the topological Dirac nodal-line semimetal BaAl4. We show that the thermoelectric power (TEP) is a sensitive probe of the multiple oscillation frequencies in this material, with two of these frequencies shown to originate from the three-dimensional Dirac band. The detected Berry phase provides evidence of the angular dependence and non-trivial state under high magnetic fields. We also have probed the signatures of Zeeman splitting, from which we have extracted the Landé -factor for this system, providing further insight into the non-trivial topology of this family of materials.
{"title":"Thermoelectric quantum oscillations and Zeeman splitting in topological Dirac semimetal BaAl4","authors":"P.R. Mandal , Kefeng Wang , Tarapada Sarkar , Prathum Saraf , Danila Sokratov , Johnpierre Paglione","doi":"10.1016/j.mtquan.2025.100054","DOIUrl":"10.1016/j.mtquan.2025.100054","url":null,"abstract":"<div><div>Three-dimensional topological semimetals hosting Dirac or Weyl fermions are a new kind of materials class in which conduction and valence bands cross each other. Such materials harbor a nontrivial Berry phase, which is an additional geometrical phase factor arising along the path of an adiabatic surface and can give rise to experimentally measurable quantities such as an anomalous Hall component. Here we report a systematic study of quantum oscillations of thermoelectric power in single crystals of the topological Dirac nodal-line semimetal BaAl<sub>4</sub>. We show that the thermoelectric power (TEP) is a sensitive probe of the multiple oscillation frequencies in this material, with two of these frequencies shown to originate from the three-dimensional Dirac band. The detected Berry phase provides evidence of the angular dependence and non-trivial state under high magnetic fields. We also have probed the signatures of Zeeman splitting, from which we have extracted the Landé <span><math><mi>g</mi></math></span>-factor for this system, providing further insight into the non-trivial topology of this family of materials.</div></div>","PeriodicalId":100894,"journal":{"name":"Materials Today Quantum","volume":"8 ","pages":"Article 100054"},"PeriodicalIF":0.0,"publicationDate":"2025-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145159185","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-25DOI: 10.1016/j.mtquan.2025.100055
Chen Zhang , Shengyuan A. Yang , Y.X. Zhao
Quantum states naturally represent symmetry groups, though often in a projective sense. Intriguingly, the projective nature of crystalline symmetries has remained underexplored until very recently. A series of groundbreaking theoretical and experimental studies have now brought this to light, demonstrating that projective representations of crystal symmetries lead to remarkable consequences in condensed matter physics and various artificial crystals, particularly in their connection to topological phenomena. In this article, we explain the basic ideas and notions underpinning these recent developments and share our perspective on this emerging research area. We specifically highlight that the appearance of momentum-space nonsymmorphic symmetry is a unique feature of projective crystal symmetry representations. This, in turn, has the profound consequence of reducing the fundamental domain of momentum space to all possible flat compact manifolds, which include torus and Klein bottle in 2D and the ten platycosms in 3D, presenting a significantly richer landscape for topological structures than conventional settings. Finally, the ongoing efforts and promising future research directions are discussed.
{"title":"Projective crystal symmetry and topological phases","authors":"Chen Zhang , Shengyuan A. Yang , Y.X. Zhao","doi":"10.1016/j.mtquan.2025.100055","DOIUrl":"10.1016/j.mtquan.2025.100055","url":null,"abstract":"<div><div>Quantum states naturally represent symmetry groups, though often in a projective sense. Intriguingly, the projective nature of crystalline symmetries has remained underexplored until very recently. A series of groundbreaking theoretical and experimental studies have now brought this to light, demonstrating that projective representations of crystal symmetries lead to remarkable consequences in condensed matter physics and various artificial crystals, particularly in their connection to topological phenomena. In this article, we explain the basic ideas and notions underpinning these recent developments and share our perspective on this emerging research area. We specifically highlight that the appearance of momentum-space nonsymmorphic symmetry is a unique feature of projective crystal symmetry representations. This, in turn, has the profound consequence of reducing the fundamental domain of momentum space to all possible flat compact manifolds, which include torus and Klein bottle in 2D and the ten platycosms in 3D, presenting a significantly richer landscape for topological structures than conventional settings. Finally, the ongoing efforts and promising future research directions are discussed.</div></div>","PeriodicalId":100894,"journal":{"name":"Materials Today Quantum","volume":"8 ","pages":"Article 100055"},"PeriodicalIF":0.0,"publicationDate":"2025-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145159187","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-11DOI: 10.1016/j.mtquan.2025.100052
Debasis Dutta , Raihan Ahammed , Yingdong Wei , Xiaokai Pan , Xiaoshuang Chen , Lin Wang , Amit Agarwal
Detecting topological phase transitions in bulk is challenging due to the limitations of surface-sensitive probes like ARPES. Here, we demonstrate that nonlinear bulk photocurrents, specifically shift and injection currents, serve as effective probes of topological transitions in noncentrosymmetric materials. These photocurrents show a robust polarity reversal across the phase transition, offering a direct optical signature that distinguishes strong topological phases from weak or trivial ones. This effect originates from a reorganization of key band geometric quantities, the Berry curvature and shift vector, on time-reversal-invariant momentum planes. Using a low-energy Dirac model, we trace this behavior to a band inversion in the time-reversal-invariant momentum plane that drives the topological transition. We validate these findings through tight-binding model for BiTe and first-principles calculations for ZrTe and BiTeI, where the topological phase can be tuned by pressure or temperature. Our results establish nonlinear photocurrent as a sensitive and broadly applicable alternative probe of topological phase transitions.
{"title":"Nonlinear bulk photocurrent probe Z2 topological phase transition in noncentrosymmetric materials","authors":"Debasis Dutta , Raihan Ahammed , Yingdong Wei , Xiaokai Pan , Xiaoshuang Chen , Lin Wang , Amit Agarwal","doi":"10.1016/j.mtquan.2025.100052","DOIUrl":"10.1016/j.mtquan.2025.100052","url":null,"abstract":"<div><div>Detecting topological phase transitions in bulk is challenging due to the limitations of surface-sensitive probes like ARPES. Here, we demonstrate that nonlinear bulk photocurrents, specifically shift and injection currents, serve as effective probes of <span><math><msub><mrow><mi>Z</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> topological transitions in noncentrosymmetric materials. These photocurrents show a robust polarity reversal across the <span><math><msub><mrow><mi>Z</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> phase transition, offering a direct optical signature that distinguishes strong topological phases from weak or trivial ones. This effect originates from a reorganization of key band geometric quantities, the Berry curvature and shift vector, on time-reversal-invariant momentum planes. Using a low-energy Dirac model, we trace this behavior to a band inversion in the time-reversal-invariant momentum plane that drives the topological transition. We validate these findings through tight-binding model for Bi<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>Te<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span> and first-principles calculations for ZrTe<span><math><msub><mrow></mrow><mrow><mn>5</mn></mrow></msub></math></span> and BiTeI, where the topological phase can be tuned by pressure or temperature. Our results establish nonlinear photocurrent as a sensitive and broadly applicable alternative probe of <span><math><msub><mrow><mi>Z</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> topological phase transitions.</div></div>","PeriodicalId":100894,"journal":{"name":"Materials Today Quantum","volume":"8 ","pages":"Article 100052"},"PeriodicalIF":0.0,"publicationDate":"2025-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145098463","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-01DOI: 10.1016/j.mtquan.2025.100053
Shah Ishmam Mohtashim
We introduce RinQ, a hybrid quantum–classical framework for identifying functionally critical residues in proteins by formulating centrality detection as a Quadratic Unconstrained Binary Optimization (QUBO) problem. Protein structures are modeled as residue interaction networks (RINs), and the QUBO formulations are solved using D-Wave’s simulated annealing. Applied to a diverse set of proteins, RinQ consistently identifies central residues that closely align with classical benchmarks, demonstrating both the accuracy and robustness of the approach.
{"title":"RinQ: Towards predicting central sites in proteins on current quantum computers","authors":"Shah Ishmam Mohtashim","doi":"10.1016/j.mtquan.2025.100053","DOIUrl":"10.1016/j.mtquan.2025.100053","url":null,"abstract":"<div><div>We introduce RinQ, a hybrid quantum–classical framework for identifying functionally critical residues in proteins by formulating centrality detection as a Quadratic Unconstrained Binary Optimization (QUBO) problem. Protein structures are modeled as residue interaction networks (RINs), and the QUBO formulations are solved using D-Wave’s simulated annealing. Applied to a diverse set of proteins, RinQ consistently identifies central residues that closely align with classical benchmarks, demonstrating both the accuracy and robustness of the approach.</div></div>","PeriodicalId":100894,"journal":{"name":"Materials Today Quantum","volume":"7 ","pages":"Article 100053"},"PeriodicalIF":0.0,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145026485","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-26DOI: 10.1016/j.mtquan.2025.100051
Jun Beom Park, Rijan Karkee, Michael Thompson Pettes
Thermoelectric materials with high electrical conductivity and low thermal conductivity (e.g., Bi2Te3) can efficiently convert waste heat into electricity. However, despite favorable theoretical predictions, individual Bi2Te3 nanostructures such as two-dimensional (2D) nanoplates tend to underperform bulk Bi2Te3. We report a novel surface doping technique to synthesize highly n-type Bi2Te3 nanoplates using an external Cr coating followed by a thermal annealing process in a reducing atmosphere, as well as the mechanism by which this surface coating – only a few atoms or less in thickness – can observably impact the thermoelectric performance of 2D Bi2Te3. The Cr atoms act as n-type carrier donors by directly incorporating into the Bi2Te3 structure during thermal annealing, enhancing electrical conductivity by ∼ 70 % while increasing thermal conductivity by only ∼ 5 % at room temperature. Compared to the uncoated Bi2Te3 nanoplate, the Cr-doped Bi2Te3 nanoplate exhibits a doubled thermoelectric figure of merit (zT), which is still relatively low. Raman spectroscopy and chemical potential simulations further confirm that Cr atoms are incorporated into the Bi2Te3 structure.
{"title":"Improved thermoelectric performance in Cr-doped two-dimensional Bi2Te3","authors":"Jun Beom Park, Rijan Karkee, Michael Thompson Pettes","doi":"10.1016/j.mtquan.2025.100051","DOIUrl":"10.1016/j.mtquan.2025.100051","url":null,"abstract":"<div><div>Thermoelectric materials with high electrical conductivity and low thermal conductivity (e.g., Bi<sub>2</sub>Te<sub>3</sub>) can efficiently convert waste heat into electricity. However, despite favorable theoretical predictions, individual Bi<sub>2</sub>Te<sub>3</sub> nanostructures such as two-dimensional (2D) nanoplates tend to underperform bulk Bi<sub>2</sub>Te<sub>3</sub>. We report a novel surface doping technique to synthesize highly n-type Bi<sub>2</sub>Te<sub>3</sub> nanoplates using an external Cr coating followed by a thermal annealing process in a reducing atmosphere, as well as the mechanism by which this surface coating – only a few atoms or less in thickness – can observably impact the thermoelectric performance of 2D Bi<sub>2</sub>Te<sub>3</sub>. The Cr atoms act as n-type carrier donors by directly incorporating into the Bi<sub>2</sub>Te<sub>3</sub> structure during thermal annealing, enhancing electrical conductivity by ∼ 70 % while increasing thermal conductivity by only ∼ 5 % at room temperature. Compared to the uncoated Bi<sub>2</sub>Te<sub>3</sub> nanoplate, the Cr-doped Bi<sub>2</sub>Te<sub>3</sub> nanoplate exhibits a doubled thermoelectric figure of merit (<em>zT</em>), which is still relatively low. Raman spectroscopy and chemical potential simulations further confirm that Cr atoms are incorporated into the Bi<sub>2</sub>Te<sub>3</sub> structure.</div></div>","PeriodicalId":100894,"journal":{"name":"Materials Today Quantum","volume":"7 ","pages":"Article 100051"},"PeriodicalIF":0.0,"publicationDate":"2025-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144908674","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-21DOI: 10.1016/j.mtquan.2025.100050
Yuanze Song , Ting Zhang , Weizhen Meng , Jing Wang , Ying Liu
Two novel three-dimensional allotropes, designated as hexagonal supertetrahedral aluminum and gallium (h-Al/h-Ga), are proposed based on a hexagonal diamond structure and share the same space group symmetry (P63/mmc) as hexagonal diamond. First-principles calculations demonstrate their structural stability and superior mechanical properties. Notably, these allotropes exhibit distinct electronic characteristics: h-Al behaves as a narrow-bandgap semiconductor, while h-Ga manifests as a topological semimetal with multiple band crossings. We systematically investigate the topological characteristics of h-Ga, which hosts three distinct classes of topological states: triple point, nodal line, and nodal surface, with associated Fermi arcs and drumhead-like surface states. Furthermore, the inclusion of spin-orbit coupling lifts all topological degeneracies, driving a phase transition to a Dirac semimetal. Our findings not only contribute to the expansion of the supertetrahedral materials family but also underscore hexagonal supertetrahedral lattices as a robust and versatile platform for the discovery of diverse topological phases.
{"title":"Hexagonal supertetrahedral gallium: a cluster-based three-dimensional topological metal","authors":"Yuanze Song , Ting Zhang , Weizhen Meng , Jing Wang , Ying Liu","doi":"10.1016/j.mtquan.2025.100050","DOIUrl":"10.1016/j.mtquan.2025.100050","url":null,"abstract":"<div><div>Two novel three-dimensional allotropes, designated as hexagonal supertetrahedral aluminum and gallium (<em>h</em>-Al/<em>h</em>-Ga), are proposed based on a hexagonal diamond structure and share the same space group symmetry (<em>P</em>6<sub>3</sub>/<em>mmc</em>) as hexagonal diamond. First-principles calculations demonstrate their structural stability and superior mechanical properties. Notably, these allotropes exhibit distinct electronic characteristics: <em>h</em>-Al behaves as a narrow-bandgap semiconductor, while <em>h</em>-Ga manifests as a topological semimetal with multiple band crossings. We systematically investigate the topological characteristics of <em>h</em>-Ga, which hosts three distinct classes of topological states: triple point, nodal line, and nodal surface, with associated Fermi arcs and drumhead-like surface states. Furthermore, the inclusion of spin-orbit coupling lifts all topological degeneracies, driving a phase transition to a Dirac semimetal. Our findings not only contribute to the expansion of the supertetrahedral materials family but also underscore hexagonal supertetrahedral lattices as a robust and versatile platform for the discovery of diverse topological phases.</div></div>","PeriodicalId":100894,"journal":{"name":"Materials Today Quantum","volume":"7 ","pages":"Article 100050"},"PeriodicalIF":0.0,"publicationDate":"2025-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144893008","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-10DOI: 10.1016/j.mtquan.2025.100049
M. Cristina Rodríguez , Analia Zwick , Gonzalo A. Álvarez
Quantum probes offer a powerful platform for exploring environmental dynamics, particularly through their sensitivity to decoherence processes. In this work, we investigate the emergence of critical behavior in the estimation of the environmental memory time , modeled as an Ornstein–Uhlenbeck process characterized by a Lorentzian spectral density. Using dynamically controlled qubit-based sensors—realized experimentally via solid-state Nuclear Magnetic Resonance (NMR) and supported by numerical simulations—we implement tailored filter functions to interrogate the environmental noise spectrum and extract from its spectral width. Our results reveal a sharp transition in estimation performance between short-memory (SM) and long-memory (LM) regimes, reflected in a non-monotonic estimation error that resembles a phase transition. This behavior is accompanied by an avoided-crossing-like structure in the estimated parameter space, indicative of two competing solutions near the critical point. These features underscore the interplay between control, decoherence, and inference in open quantum systems. Beyond their fundamental significance, these critical phenomena offer a practical diagnostic tool for identifying dynamical regimes and optimizing quantum sensing protocols. By exploiting this criticality, our findings pave the way for adaptive control strategies aimed at enhancing precision in quantum parameter estimation—particularly in complex or structured environments such as spin networks, diffusive media, and quantum materials.
{"title":"Manifestation of critical effects in environmental parameter estimation using a quantum sensor under dynamical control","authors":"M. Cristina Rodríguez , Analia Zwick , Gonzalo A. Álvarez","doi":"10.1016/j.mtquan.2025.100049","DOIUrl":"10.1016/j.mtquan.2025.100049","url":null,"abstract":"<div><div>Quantum probes offer a powerful platform for exploring environmental dynamics, particularly through their sensitivity to decoherence processes. In this work, we investigate the emergence of critical behavior in the estimation of the environmental memory time <span><math><msub><mrow><mi>τ</mi></mrow><mrow><mi>c</mi></mrow></msub></math></span>, modeled as an Ornstein–Uhlenbeck process characterized by a Lorentzian spectral density. Using dynamically controlled qubit-based sensors—realized experimentally via solid-state Nuclear Magnetic Resonance (NMR) and supported by numerical simulations—we implement tailored filter functions to interrogate the environmental noise spectrum and extract <span><math><msub><mrow><mi>τ</mi></mrow><mrow><mi>c</mi></mrow></msub></math></span> from its spectral width. Our results reveal a sharp transition in estimation performance between short-memory (SM) and long-memory (LM) regimes, reflected in a non-monotonic estimation error that resembles a phase transition. This behavior is accompanied by an avoided-crossing-like structure in the estimated parameter space, indicative of two competing solutions near the critical point. These features underscore the interplay between control, decoherence, and inference in open quantum systems. Beyond their fundamental significance, these critical phenomena offer a practical diagnostic tool for identifying dynamical regimes and optimizing quantum sensing protocols. By exploiting this criticality, our findings pave the way for adaptive control strategies aimed at enhancing precision in quantum parameter estimation—particularly in complex or structured environments such as spin networks, diffusive media, and quantum materials.</div></div>","PeriodicalId":100894,"journal":{"name":"Materials Today Quantum","volume":"7 ","pages":"Article 100049"},"PeriodicalIF":0.0,"publicationDate":"2025-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144831158","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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