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In recent years, there has been significant development in acoustic waveguides through the introduction of topological phase correlation concepts in acoustics. Many studies have shown the properties of acoustic unidirectional transmission. This paper presents a new ring-shaped acoustic topological insulator that is multi-band, unlike previous structures. The structure improves internal space utilization with the same dimensions, reducing acoustic wave conduction frequency in air environments. Additionally, the introduction of a multistage ring-shaped resonant cavity enables the conduction of acoustic waves in multiple frequency bands. This paper employs the rotational scattering mechanism to invert the topological phase of the lattice. This allows for the construction of two crystals with opposite phases, which can be used to create a topological channel for the transmission of acoustic waves. At the topological interface, the acoustic transmission losses within the four bands are small. Furthermore, this paper verifies by simulation that the defects have little effect on acoustic transmission. The paper's research offers potential for multiband acoustic control. [ABSTRACT FROM AUTHOR]

The field of topological protected wave engineering, inspired by quantum mechanics, has generated significant interest. Acoustic analogs of electronic topological insulators provide new opportunities for manipulating sound propagation with unconventional acoustic edge modes that are immune to backscattering. Numerous reports have been published on the design of two-dimensional acoustic topological insulators (ATIs). However, the sound path of a two-dimensional design is simple, and its ability to control sound waves is limited. On the other hand, the design of 3D ATIs is relatively complex, making it difficult to manufacture and limiting its versatility. Based on the design idea of the 2D ATIs, inspired by the art named 3D pin-sculpture, an adjustable structure of a finite size consisting of spindle-shaped units with a variable cross section is designed to realize flexible path transformation. Furthermore, unlike two-dimensional structural defects, such as cavities and disorder, the analysis of vertical dislocation defects in finite-sized structures allows for the design of local sound propagation along the z-direction, providing a concept for constructing a stereo path. The designed structure also serves two functions: acoustic switch and delay. This idea offers an alternative approach to designing complex sound transmission paths. [ABSTRACT FROM AUTHOR]

A series of topological insulators (TIs) based saturable absorbers (SAs), e.g., Bi2Se3, Bi2SeTe2, and Bi4Br4, are confirmed to exhibit excellent non-linear optical response due to the topological edge states. Here, we demonstrate how a topological crystalline insulator, SnTe thin films, can be prepared on highly oriented pyrolytic graphite and gold-plated mirrors through molecular beam epitaxy. SnTe-SAs incorporated into Er-doped fiber lasers exhibit a large modulation depth of 27.2% and accomplish mode-locking at 1558 nm with a pulse width of 319 fs, indicating preeminent nonlinear optical performance among the reported TI-based SAs. This work illuminates the preparation of SnTe thin films and demonstrates the great potential of SnTe films in ultrafast optical devices. [ABSTRACT FROM AUTHOR]

In the present study, we have investigated the effect of magnetic Cr doping on the transport properties of a sputtered Bi2Se3 thin film on the SrTiO3 (110) substrate. The high-resolution x-ray diffraction and Raman spectroscopy measurements revealed the growth of rhombohedral Bi2Se3 thin films. Further electronic and compositional analysis was done by x-ray photoemission spectroscopy and Rutherford backscattering spectroscopy, and the x-value was estimated to be 0.18 in the Bi2−xCrxSe3 thin film. The variation in the resistivity with temperature (2–300 K) revealed the metallic nature in undoped Bi2Se3 up to 30 K and upturn resistivity below 30 K. The Cr-doped Bi2Se3 resistivity data show a traditional semiconducting nature up to 25 K and take an abrupt upturn resistivity below 25 K. The resistivity behavior of both samples was explained by adopting a model that consists of the total resistance, a combination of bulk and surface resistance in parallel. The bulk bandgap value determined by this method is obtained to be 256 meV in an undoped Bi2Se3 thin film. Magnetoconductance data of the undoped thin film revealed a weak anti-localization (WAL) effect, while the Cr-doped thin film showed a weak localization (WL) effect at low temperatures (<50 K). At low magnetic field and low temperature, a competing nature of WAL and WL effects was prominent in the Cr-doped film. A drastic increase in the electrical resistance suggests that Cr doping can significantly modify the electrical properties of Bi2Se3 thin films, which could have potential applications in futuristic devices. [ABSTRACT FROM AUTHOR]

Transition metal catalysts supported on topological insulators are predicted to show improved catalytic properties due to the presence of topological surface states, which may float up to the catalysts and provide robust electron transfer. However, experimental studies of surface structures and corresponding catalytic properties of transition metal/topological insulator heterostructures have not been demonstrated so far. Here, we report the structures, chemical states, and adsorption behaviors of two conventional transition metal catalysts, Pt and Pd, on the surface of Bi2Se3, a common topological insulator material. We reveal that Pt forms nanoparticles on the Bi2Se3 surface. Moreover, the interaction between Pt and surface Se is observed. Furthermore, thermal dosing of O2 onto the Pt/Bi2Se3 heterostructure leads to no oxygen adsorption. Detailed scanning tunneling microscopy study indicates that Pt transforms into PtSe2 after the thermal process, thus preventing O2 from adsorption. For another transition metal Pd, it exhibits approximate layer-island growth on Bi2Se3, and Pd–Se interaction is also observed. Our work provides significant insights into the behaviors of transition metals on top of a common topological insulator material and will assist in the future design of catalysts built with topological materials. [ABSTRACT FROM AUTHOR]

The binary high-pressure phase diagram of the Ta–Sb system was constructed for the first time in this study, utilizing the evolutionary algorithm USPEX and density functional theory (DFT). Ten pressurized dynamically and mechanically stable or metastable novel phases of Ta–Sb were discovered, including I4/mmm-TaSb2, P4/nmm-TaSb, P-3-Ta2Sb7, I4/mmm-Ta2Sb3, P-4m2-Ta7Sb, Pm-3-Ta7Sb, Pmm2-Ta15Sb, P4/nmm-TaSb3, I4/mmm-Ta3Sb4, and I4/mmm-Ta2Sb5. The compounds P-4m2-Ta7Sb and Pmm2-Ta15Sb exhibit promising characteristics as non-centrosymmetric superconductors (NCSs), with their superconducting critical temperature (TC) being 3.831 and 3.221 K, respectively. The application of pressure tuning is predicted to transform the topological characteristics of P4/nmm-TaSb, causing it to transition from a topological insulator state to a Dirac semimetal state and ultimately reverting back to a topological insulator state. Therefore, the P4/nmm-TaSb compound is considered a promising candidate to investigate topological and superconducting excitations. Moreover, the mechanical and thermal properties of Ta–Sb binary phases were also investigated. The thermal conductivity of I4/mmm-TaSb2, P4/nmm-TaSb, and P4/nmm-TaSb3 all surpasses 20 W m−1 K−1 at 1000 K, showcasing their excellent thermal conductivity properties. The present study addresses the research gap concerning high-pressure structures in the Ta–Sb binary system, thereby offering valuable insights for the design and development of intermetallic compounds within this binary system. [ABSTRACT FROM AUTHOR]

The giant spin–orbit torque (SOT) generated by topological surface states in topological insulators (TIs) provides an energy-efficient writing method for magnetic memory. In this study, we demonstrate a topological insulator/spin valve (TI/SV) device that operates at room temperature. An ultrathin, high-quality TI (Bi0.5Sb0.5)2Te3 (BST) thin film is epitaxially grown as a functional layer on a (0001)-Al2O3 substrate via molecular beam epitaxy in ultrahigh vacuum. Subsequently, Ta/CoFe/Cu/CoFe/IrMn layers are grown on BST/Al2O3 thin films using magnetron sputtering to form TI/SV devices via a subsequent standard lithography process. The resulting TI/SV devices exhibit a giant magnetoresistance of up to ∼1.1% at room temperature. Additionally, a low switching current density of approximately 1.25 × 105 A cm−2 is achieved, which implies high potential for further reducing the energy consumption of SOT-based devices. The SOT conversion efficiency and charge-spin conversion efficiency of the TI layer are approximately 4.74 × 10−6 Oe A−1 cm2 and 1.33, respectively, as extracted from the SOT-induced shift of the magnetic switching field. Moreover, the switching current density reduces steadily with the device size scaling down. This study can facilitate the realization of energy-efficient magnetic memory devices in the future. [ABSTRACT FROM AUTHOR]

Transition metal catalysts supported on topological insulators are predicted to show improved catalytic properties due to the presence of topological surface states, which may float up to the catalysts and provide robust electron transfer. However, experimental studies of surface structures and corresponding catalytic properties of transition metal/topological insulator heterostructures have not been demonstrated so far. Here, we report the structures, chemical states, and adsorption behaviors of two conventional transition metal catalysts, Pt and Pd, on the surface of Bi2Se3, a common topological insulator material. We reveal that Pt forms nanoparticles on the Bi2Se3 surface. Moreover, the interaction between Pt and surface Se is observed. Furthermore, thermal dosing of O2 onto the Pt/Bi2Se3 heterostructure leads to no oxygen adsorption. Detailed scanning tunneling microscopy study indicates that Pt transforms into PtSe2 after the thermal process, thus preventing O2 from adsorption. For another transition metal Pd, it exhibits approximate layer-island growth on Bi2Se3, and Pd–Se interaction is also observed. Our work provides significant insights into the behaviors of transition metals on top of a common topological insulator material and will assist in the future design of catalysts built with topological materials. [ABSTRACT FROM AUTHOR]

Higher-order topological states, as emergent topological phases of matter, originating from condensed matter physics, have sparked a vibrant exploration of topological insulators. Their topologically protected multidimensional localized states are typically associated with nontrivial bulk band topology, and the significant impact of lattice geometry is unconsciously overlooked. Here, we construct coupled acoustic cavities on a two-dimensional honeycomb lattice to investigate the sensitivity of higher-order topological modes to the variations of edge contour. Fractional charge is utilized to accurately predict topological modes with distinct topological orders, in spite of the minimal bulk bandgaps inherent in the honeycomb lattice and bound states in the continuum. It is found that the presence and absence of the first-order and higher-order topological modes in the same topological phase are tightly linked to the sample boundaries, which can be demonstrated by both theoretical analysis and numerical calculation. Our study also discusses potential physical realization of geometry-dependent topological states across different platforms, providing inspiration for the prospective application of topological devices in acoustics. [ABSTRACT FROM AUTHOR]

High Chern number topological insulators can be obtained in a film of layered magnetic block system theoretically and experimentally. With nonzero Chern numbers, Chern insulators become valuable for fundamental topological physics and for improving next-generation electronic devices. We study energy and angular momentum radiation from layered topological insulators using the Dirac Fermion approach and by Green's function method. We make a connection between radiation magnitude and topological phase transitions. We find that the magnetic exchange field, intra-layer coupling, and inter-layer interaction are efficient measures to modify the energy radiation of layered topological materials. Moreover, the magnetic exchange field is indispensable for emitting angular momentum due to the need for breaking time-reversal symmetry. [ABSTRACT FROM AUTHOR]

The realization of remarkable thermoelectric (TE) properties in a novel single-crystalline quantum material is a topic of prime interest in the field of thermoelectricity. It necessitates a proper understanding of transport properties under magnetic field and magnetic properties at low field. We report polarized Raman spectroscopic study, TE properties, and magneto-resistance (MR) along with magnetic characterization of single-crystalline Bi2Se3. Polarized Raman spectrum confirms the strong polarization effect of A 1 g 1 and A 1 g 2 phonon modes, which verifies the anisotropic nature of the Bi2Se3 single crystal. Magnetization measurement along the in-plane direction of single crystal divulges a cusp-like paramagnetic response in susceptibility plot, indicating the presence of topological surface states (TSSs) in the material. In-depth MR studies performed in different configurations also confirm the presence of anisotropy in the single-crystalline Bi2Se3 sample. A sharp rise in MR value near zero magnetic field and low-temperature regime manifests a weak anti-localization (WAL) effect, depicting the quantum origin of the conductivity behavior at low temperature. Moreover, in-plane magneto-conductivity data at low-temperature (up to 5 K) and low-field region (≤15 kOe) confirm the dominance of the WAL effect (due to TSS) with a negligible bulk contribution. Quantum oscillation (SdH) in magneto-transport data also exhibits the signature of TSS. Additionally, an exceptional TE power factor of ∼950 μW m−1 K−2 at 300 K is achieved, which is one of the highest values reported for pristine Bi2Se3. Our findings pave the way for designing single crystals, which give dual advantages of being a good TE material along with a topological insulator bearing potential application. [ABSTRACT FROM AUTHOR]

The body–boundary correspondence refers to the relationship between the body and boundary states of topological insulators (TIs). In TIs, the presence of boundary states is connected to the bulk topological properties of the material. The topology can be identified by studying the energy of the topological modes within the bulk bandgap. However, not all topological materials exhibit boundary states within the insulating energy gap. In many cases, the presence of boundary states can be hidden or masked by the bulk energy bands, making it difficult to measure TIs. Recent experiments have shown that defects, which are commonly found in crystalline materials, can be used as probes to explore higher-order topologies that have been recently realized on various platforms. These defects can generate fractional charges and stable bound states in the dispersion region, allowing us to observe the clear body–disclination correspondence. We have performed simulations using a coupled acoustic cavity system with C3 and C5 symmetries to investigate the body–disclination correspondence in topological crystal insulators (TCIs) in the field of acoustics. Simulation and theoretical results have demonstrated that defects such as disclinations can be used to probe higher-order topologies that were previously unobservable in three-dimensional structures. This approach allows us to detect fractional mode charges and stable bound states, which are crucial for understanding the topological nature of TCIs. Our work demonstrates the potential of using disclination defects to study the intricate relationship between the body and boundary states in topological materials, particularly in the context of acoustics. [ABSTRACT FROM AUTHOR]

We study theoretically the electronic structure of three-dimensional (3D) higher-order topological insulators in the presence of step edges. We numerically find that a 1D conducting state with a helical spin structure, which also has a linear dispersion near the zero energy, emerges at a step edge and on the opposite surface of the step edge. We also find that the 1D helical conducting state on the opposite surface of a step edge emerges when the electron hopping in the direction perpendicular to the step is weak. In other words, the existence of the 1D helical conducting state on the opposite surface of a step edge can be understood by considering an addition of two different-sized independent blocks of 3D higher-order topological insulators. On the other hand, when the electron hopping in the direction perpendicular to the step is strong, the location of the emergent 1D helical conducting state moves from the opposite surface of a step edge to the dip (270 ° edge) just below the step edge. In this case, the existence at the dip below the step edge can be understood by assigning each surface with a sign (+ or −) of the mass of the surface Dirac fermions. These two physical pictures are connected continuously without the bulk bandgap closing. Our finding paves the way for on-demand creation of 1D helical conducting states from 3D higher-order topological insulators employing experimental processes commonly used in thin-film devices, which could lead to, e.g., a realization of high-density Majorana qubits. [ABSTRACT FROM AUTHOR]

We investigate the finite size effects of a three-dimensional second-order topological insulator with fourfold rotational symmetry and time-reversal symmetry. Starting from the effective Hamiltonian of the three-dimensional second-order topological insulator, we derive the effective Hamiltonian of four two-dimensional gapped surface states by perturbative methods. Then, the sign alternation of the mass term of the effective Hamiltonian on the adjacent surface leads to the hinge state. In addition, we obtain the effective Hamiltonian and its wave function of one-dimensional gapless hinge states with semi-infinite boundary conditions based on the effective Hamiltonian of two-dimensional surface states. In particular, we find that the hinge states on the two sides of the same surface can couple to produce a finite energy gap. [ABSTRACT FROM AUTHOR]

Recently, acoustic valley Hall topological insulators have become a cutting-edge area of acoustic physics, where the topological phase transition in phononic crystals shows the presence of band inversion through the Dirac point in the momentum space. We developed a 2D hexagonal lattice chiral phononic crystal using reconfigurable construction by extending one side of the original rectangular rods. When the variation of the side length was from left to right, the topological phase transition is triggered by reopening the Dirac degeneracies beyond high-symmetry points in the first Brillouin zone. We numerically showed valley edge state's propagation through the interface bent toward distinct chiral topological phononic crystals. Moreover, we assembled 2 × 2 cross-waveguides with a defect cavity based on double heterostructure interfaces. The simulated results verify that the phase change is achieved by the directional coupling switching. This research possibly paves the way for exploiting valley edge states to design the complex acoustic waveguide. [ABSTRACT FROM AUTHOR]

Photonic topological insulators have been widely studied due to the robustness of energy transport via supported edge modes immune to structural disorder. In this work, a topological gap waveguide is constructed by introducing line defect into a topological photonic crystal structure and combining it with a gap waveguide structure, the design of which, therefore, combines the advantages of both topological and gap waveguides. Not only does it give high transmission efficiency but it also enables high robustness for energy transmission under structural defects and sharp bends. Our proposed topological waveguide design can be implemented with conventional semiconductor technology and integrated into optical circuits for communication systems. [ABSTRACT FROM AUTHOR]

Phonon occupation is temperature (T) dependent; it may participate in scattering with electronic states of topological insulators (TIs). Longitudinal optical (LO) phonons A1g1$$ {\mathrm{A}}_{1g}^1 $$ and A1g2$$ {\mathrm{A}}_{1g}^2 $$ in Bi2 − xSbxTe3 − ySey (BSTS) was resonantly excited by a photon energy (Ep) 2.33 eV due to electronic transition of unoccupied conduction band. The intensity of these modes was enhanced in Bi2Te3 film at Ep 1.87 eV, which is close to the electronic transition of unoccupied Dirac states. Fröhlich coupling strength was the main mechanism for higher intensity of A1g1$$ {\mathrm{A}}_{1g}^1 $$ and A1g2$$ {\mathrm{A}}_{1g}^2 $$ modes. At 300 K, the intensity of the A1g2$$ {\mathrm{A}}_{1g}^2 $$ mode was significantly decayed in both the BSTS and Bi2Te3 at Ep 2.33 and 1.87 eV due to the anharmonic coupling. However, at similar value of T, spectral profile of A1g1$$ {\mathrm{A}}_{1g}^1 $$ and Eg2$$ {\mathrm{E}}_g^2 $$ modes was not affected because of the lower probability of decay rate of these phonons. In resonant condition, well‐resolved Raman forbidden surface modes were observed at T of 50 K. At 300 K, more asymmetric Fano profile of surface phonon was observed due to the anharmonic coupling. The study indicated that at high T, A1g1$$ {\mathrm{A}}_{1g}^1 $$ mode and anharmonic coupling may become primary cause for scattering with electronic states of the TIs. However, at low T, primarily, both the LO phonons participated in the scattering. [ABSTRACT FROM AUTHOR]

Hybrid-order topological insulators combine first- and higher-order topological properties and host topological boundary states with codimension one and more than one in different bandgaps. A Weyl semimetal (WSM) can possess two types of Weyl points: one class of Weyl points terminates the Fermi arc surface states, while another class of Weyl points not only launch Fermi arc surface states but also hinge arc states, exhibiting the hybrid-order topology. Here, we propose a hybrid-order WSM by stacking two-dimensional rhomboid lattices based on chiral nearest-neighbor and double-helix next-nearest interlayer couplings. The first type of Weyl point that only truncates the Fermi arc surface states exists at the crossing of any two-fold degeneracy of two adjacent bands, and the second type of Weyl point that connects the hinge arc states only appears at the crossing of the two middle bands. Our findings enrich the classification of topological semimetals in condensed matter physics. [ABSTRACT FROM AUTHOR]

Recently, topolectrical circuits (TECs) boom in studying the topological states of matter. The resemblance between circuit Laplacians and tight-binding models in condensed matter physics allows for the exploration of exotic topological phases on the circuit platform. In this review, we begin by presenting the basic equations for the circuit elements and units, along with the fundamentals and experimental methods for TECs. Subsequently, we retrospect the main literature in this field, encompassing the circuit realization of (higher-order) topological insulators and semimetals. Due to the abundant electrical elements and flexible connections, many unconventional topological states like the non-Hermitian, nonlinear, non-Abelian, non-periodic, non-Euclidean, and higher-dimensional topological states that are challenging to observe in conventional condensed matter physics, have been observed in circuits and summarized in this review. Furthermore, we show the capability of electrical circuits for exploring the physical phenomena in other systems, such as photonic and magnetic ones. Importantly, we highlight TEC systems are convenient for manufacture and miniaturization because of their compatibility with the traditional integrated circuits. Finally, we prospect the future directions in this exciting field, and connect the emerging TECs with the development of topology physics, (meta)material designs, and device applications. [ABSTRACT FROM AUTHOR]

Altermagnetism emerges as the third fundamental collinear magnetism recently. Associating nontrivial topology and quantum orders to this newly established magnetism is an important physical topic and may lead to interesting physics such as unusual quantum spin Hall effect with time-reversal-symmetry breaking, topological superconductivity and spin-valley locking. Here, we first generalize the spinless Haldane model from the usual honeycomb lattice to the otherwise simpler square lattice. We then restore the doublet spin degree of freedom, the resulted spinful model resembles the Kane-Mele model and is able to describe the unprecedented physics which intertwine C -paired spin-valley locking, Dirac physics, nontrivial band topology and altermagnetism. Our works shed lights on future studies and applications in spintronics and valleytronics for altermagnetic materials, the lattice theories developed in this article may also find their broad applications to optical lattice with ultra cold atoms, photonic lattice, etc. other than the usual electronic systems. [ABSTRACT FROM AUTHOR]

Semiconductor heterojunctions have garnered extensive interest in photocatalytic hydrogen generation, yet the limited light absorption and charge transfer efficiencies still restrict the photocatalytic performance. The topological insulator has unique surface states and high‐mobility electrons, demonstrating the significant potential for enhancing photocatalysis. Herein, a ternary photocatalyst based on a topological insulator, in which CdS and ZnS nanoparticles are grown on Bi2Se3 nanotube, is prepared for efficient photocatalysis driven by topological surface state for the first time. Under simulated solar light irradiation, the CdS/ZnS/Bi2Se3 nanotubes display a robust photocatalytic hydrogen production rate of 7.13 mmol h−1 g−1, which is 69.2 times of CdS and comparable to many CdS‐based photocatalysts. The unique hollow structure, topological surface state of Bi2Se3, and cooperative bandgap excitations of the three components endow the hybrids with wide light response to harvest solar energy. Meanwhile, the multichannel charge transfer facilitated by topological surface state and internal electric fields within the hybrids effectively suppresses the recombination of the photogenerated charge carriers. This mechanism maintains a high concentration of stable electrons on Bi2Se3, resulting in highly efficient hydrogen production. This work provides a new inspiration for designing heterojunction photocatalysts based on topological insulators for high‐efficiency solar‐driven energy conversion. [ABSTRACT FROM AUTHOR]

Rich momentum-dependent electronic structure naturally arises in solids with long-range crystalline symmetry. Reliable and scalable quantum technologies rely on materials that are either not perfect crystals or non-crystalline, breaking translational symmetry. This poses the fundamental questions of whether coherent momentum-dependent electronic states can arise without long-range order, and how they can be characterized. Here we investigate Bi2Se3, which exists in crystalline, nanocrystalline, and amorphous forms, allowing direct comparisons between varying degrees of spatial ordering. Through angle-resolved photoemission spectroscopy, we show for the first time momentum-dependent band structure with Fermi surface repetitions in an amorphous solid. The experimental data is complemented by a model that accurately reproduces the vertical, dispersive features as well as the replication at higher momenta in the amorphous form. These results reveal that well-defined real-space length scales are sufficient to produce dispersive band structures, and that photoemission can expose the imprint of these length scales on the electronic structure. Recent studies showing dispersive surface states in an amorphous topological insulator has deepened the understanding of momentum-space electronic structure. Here the authors report dispersive electronic states and a distinct Fermi surface with Brillouin-zone-like repetitions in amorphous Bi2Se3. [ABSTRACT FROM AUTHOR]

Non-Hermitian Dirac point plays an important role in topological transition as their Hermitian counterpart and connect non-Hermitian physics with band topology. Instead of being exceptional point or exceptional ring, we here reveal that the Dirac points can be survived in the presence of gain and loss obeying anti-parity-time symmetry based on the two-dimensional inclined Su–Schrieffer–Heeger model. Particularly, such non-Hermitian parameters enable the engineering of non-Hermitian Dirac states, including shift of the Dirac points and topological transition from Dirac semimetal to weak topological insulator. We experimentally demonstrate these non-Hermitian Dirac states in acoustic crystal, where the gain and loss are, respectively, controlled by the active acoustic components and absorbing materials. Through varying the strength of gain and loss, the shifting and opening of the Dirac points, together with topological edge states, are observed. Our system serves as an ideal and highly tunable platform for exploring the non-Hermitian topological physics and has potential applications in designing acoustic devices. [ABSTRACT FROM AUTHOR]

Spintronics, micro/nanofabrication, and the semiconductor industry are undergoing significant transformations, highlighting the need for flexible technologie. This study examines the possibility of integrating topological insulators (TIs), specifically Bi2Te3 thin films (13–191 nm), into flexible spintronic applications through scalable magneto‐sputtering techniques, and investigates how structural organization influences electrical and topological properties through post‐thermal annealing. Films annealed above 250 °C display improved polycrystalline structure, larger crystallites, fewer local defects, and higher a room‐temperature Seebeck coefficient (S) and resistivity (ρ), suggesting decreased bulk electronic contributions. A metastable transport regime is identified in the temperature‐dependent resistivity of films annealed at 300 °C between 20–100 K; in this range, the thinnest film exhibits markedly metallic behavior, signaling the presence of topological surface states (TSS). Magnetoresistance measurements of as‐grown and annealed films, between 3–20 K, demonstrate weak antilocalization. Applying the Hikami‐Larkin‐Nagaoka model, α‐coefficients are found to scale with thickness from 0.5–1, indicating thickness‐controlled coupling of the TSS. Post‐annealing at 300 °C, the phase coherence length, Lϕ, of the thinner films increases, while the temperature dephasing rate shifts from ∼0.7 (as‐grown) to ∼0.5 (post‐annealing), aligning with expected values for 2D TSS. These are encouraging findings for large‐scale manufacturing flexible TI technologies, without sacrificing tunabilit. [ABSTRACT FROM AUTHOR]

The Stiefel–Whitney (SW) insulator, which lacks spin‐orbit coupling and has space–time inversion (PT$\text{PT}$) symmetry, has attracted significant interest due to its fragile topological state and unconventional bulk‐boundary correspondence. Previously, the identification of SW insulators has been widely proposed for 2D phononic systems, but it has received little attention for 3D phononic systems. Herein, it is recognized that the 3D 3,44T19 type carbon allotrope (3,44T19‐CA) possesses the possibility to attain the nontrivial phononic SW topology characterized by a nontrivial second SW number, specifically w2 = 1. In addition, the 3D 3,44T19‐CA has 2D surface vibrational modes and 1D hinge vibrational modes, providing an excellent platform for multi–dimensional topological phononic boundaries research. [ABSTRACT FROM AUTHOR]

The report carried out detailed first‐principle calculations of Mercury chalcogenides (HgX; X = Te, Se and S) using density functional theory, verifying the bulk band inversion property with different exchange‐correlation functionals. The Wannier function method is used to study the non‐trivial topology of HgX systems, spin Berry curvature, and intrinsic spin Hall conductivity. Quantized intrinsic spin Hall conductivity is observed in the HgX systems. Large intrinsic spin Hall conductivity is found in the systems due to a strong spin Berry curvature accumulation near the triply degenerate points in the Brillouin zone. Calculation shows that the intrinsic spin Hall conductivity for all three HgX systems has stable plateaus, with Mercury Telluride having a maximum width of up to 1.05 eV. The maximum intrinsic spin Hall conductivity of –931ℏ$\hbar$/e (Scm−1${\rm Scm}^{-1}$) is obtained in mercury sulfide, higher than the reported values for spin Hall conductivity and the plateau width in typical topological insulators such as Bi2Se3$\text{Bi}_{2}\text{Se}_{3}$, Bi2Te3$\text{Bi}_{2}\text{Te}_{3}$, and Sb2Se3$\text{Sb}_{2}\text{Se}_{3}$ as well as in transition metal pnictides (TaX, X = As, P and N) and transition metal iridates. [ABSTRACT FROM AUTHOR]

Higher‐order topological insulators (HOTIs) have attracted much attention in photonics partly because of the robust and highly confined corner modes they support. The growing availability of synthetic multi‐orbital platforms has recently stimulated research focus on the interplay between HOTIs and orbital degree of freedom. In this work, the topological properties of the two‐dimensional (2D) Su–Schrieffer–Heeger (SSH) model with p$p$‐orbital degree of freedom are explored and p$p$‐orbital topological corner states in a laser‐written photonic 2D SSH lattice are experimentally observed. It is shown that the p$p$‐band 2D SSH model is a HOTI, where zero‐energy orbital corner states appear either as in‐gap states or as bound states in the continuum (BICs). Chiral symmetry is sufficient for topological protection of the in‐gap p$p$‐orbital corner states, but not for their BIC counterparts because of the hybridization effect within the bulk continuum. The multipole chiral number is employed as an optimal topological invariant to characterize the p$p$‐orbital HOTIs. The flexibility of tuning the orbital couplings offers an extra degree of manipulation for the BICs, which may be useful for the development of novel photonic devices. [ABSTRACT FROM AUTHOR]

Kagome lattices have garnered significant interest over the decades due to their rich physics and implications for exotic superconductors and topological materials. In particular, the so‐called "breathing Kagome lattice" (BKL) is often used as a prototypical model to understand higher‐order topological insulators. Here it is demonstrated that higher‐order corner states exist in a specially distorted Kagome lattice, resembling the "Inverse Hexagram" lattice distortion originally introduced in the study of charge density waves in Kagome metals. Importantly, it is found that such an Inverse Hexagram‐like Kagome lattice with C6 rotational symmetry hosts two types of in‐gap corner states, in contrast to a flat‐cutting BKL of C3 symmetry that supports only one type of corner state under the tight‐binding condition. It is shown that the nontrivial corner states exhibit a fractional corner anomaly, revealing the feature of higher‐order topology. Using laser‐written waveguide lattices as a photonic platform, these two types of corner states are experimentally observed, along with a direct comparison with the corner excitation at their trivial counterparts. Experimental observations are further corroborated by numerical simulations and stability analysis under random perturbation. These results may prove relevant and applicable to similar phenomena in other Kagome platforms beyond photonics. [ABSTRACT FROM AUTHOR]

Interferometers and beam splitters are fundamental building blocks for photonic neuromorphic and quantum computing machinery. In waveguide‐based photonic integrated circuits, beam‐splitting is achieved with directional couplers that rely on transition regions where the waveguides are adiabatically bent to suppress back‐reflection. In this study, a novel, compact approach for introducing guided mode coupling is presented. Along the multimodal domain wall between topological photonic crystals, the photonic spin is conserved to suppress back‐reflection, and the topological protection of the valley degree of freedom is relaxed to implement tunable beam splitting. Rapid advancements in chip‐scale topological photonics suggest that the proposed simultaneous utilization of multiple topological degrees of freedom could benefit the development of novel photonic computing platforms. [ABSTRACT FROM AUTHOR]

Robust edge states and corner states in photonic topological insulators provide effective ways to manipulate the propagation of electromagnetic waves. Bandgaps of the previously reported photonic topological insulators are independent of each other. In this paper, a higher‐order valley photonic insulator composed of arrays of dendritic structure is designed. The band structure shows an overlapped bandgap is observed, and the overlapped bandgap divides the band structure into three bandgaps. The evolution of the overlapped bandgap is investigated by changing the geometric parameters and increasing the fractal to break the C3v symmetry drastically. Besides, it is notable that the band structure of the proposed valley photonic insulator is flat bands. It is demonstrated that undistorted transmission can be observed as a plane electromagnetic wave transmits through the proposed valley photonic insulator. The interface consisting of two valley photonic structures with distinct topological nontrivial phases is constructed. Edge states and corner states with strong energy localization are obtained in multi‐band frequencies. Remarkably, two triangular structures with different Wannier center configurations both have corner states in the same bandgap, which does not obey the valley selectivity. The phenomenon is caused by the weak valley locking property due to the overlapped bandgap. The proposed valley photonic insulators are expected to benefit applications in optical devices such as topological lasers. [ABSTRACT FROM AUTHOR]

Topological crystalline insulators are known to support multiple Majorana zero modes (MZMs) at a single vortex, their hybridization is forbidden by a magnetic mirror symmetry M T . Due to the limited energy resolution of scanning tunneling microscopes and the very small energy spacing of trivial bound states, it remains challenging to directly probe and demonstrate the existence of multiple MZMs. In this work, we propose to demonstrate the existence of MZMs by studying the hybridization of multiple MZMs in a symmetry breaking field. The different responses of trivial bound states and MZMs can be inferred from their spatial distribution in a vortex. However, the theoretical simulations are very demanding since it requires an extremely large system in real space. By utilizing the kernel polynomial method, we can efficiently simulate large lattices with over 108 orbitals to compute the local density of states which bridges the gap between theoretical studies based on minimal models and experimental measurements. We show that the spatial distribution of MZMs and trivial vortex bound states differs drastically in tilted magnetic fields. The zero-bias peak elongates when the magnetic field preserves M T , while it splits when M T is broken, giving rise to an anisotropic magnetic response. Since the bulk of SnTe are metallic, we also study the robustness of MZMs against the bulk states, and clarify when can the MZMs produce a pronounced anisotropic magnetic response. [ABSTRACT FROM AUTHOR]

While ∼30% of materials are reported to be topological, topological insulators are rare. Magnetic topological insulators (MTI) are even harder to find. Identifying crystallographic features that can host the coexistence of a topological insulating phase with magnetic order is vital for finding intrinsic MTI materials. Thus far, most materials that are investigated for the determination of an MTI are some combination of known topological insulators with a magnetic ion such as MnBi2Te4. Motivated by the recent success of EuIn2As2, the role of chemical pressure on topologically trivial insulator is investigated, Eu5In2Sb6 via Ga substitution. Eu5Ga2Sb6 is predicted to be topological but is synthetically difficult to stabilize. The intermediate compositions between Eu5In2Sb6 and Eu5Ga2Sb6 are observed through theoretical works to explore a topological phase transition and band inversion mechanism. The band inversion mechanism is attributed to changes in Eu–Sb hybridization as Ga is substituted for In due to chemical pressure. Eu5In4/3Ga2/3Sb6 is also synthesized, the highest Ga concentration in Eu5In2‐xGaxSb6, and report the thermodynamic, magnetic, transport, and Hall properties. Overall, the work paints a picture of a possible MTI via band engineering and explains why Eu‐based Zintl compounds are suitable for the co‐existence of magnetism and topology. [ABSTRACT FROM AUTHOR]

We predict a half-quantized mirror Hall effect induced by mirror symmetry in strong topological insulator films. These films are known to host a pair of gapless Dirac cones in the first Brillouin zone associated with surface electrons. Our findings reveal that mirror symmetry assigns a unique mirror parity to each Dirac cone, resulting in a half-quantized Hall conductance of ± e 2 2 h for each cone. Despite the total electrical Hall conductance being null due to time-reversal invariance, the difference in the Hall conductance between the two cones yields a quantized Hall conductance of e 2 h for the difference in mirror currents. The effect of helical edge mirror current - a crucial feature of this quantum effect - may, in principle, be determined by means of electrical measurements. The half-quantum mirror Hall effect reveals a type of mirror-symmetry induced quantum anomaly in a time-reversal invariant lattice system, giving rise to a topological metallic state of matter with time-reversal invariance. Symmetry considerations can give rise to various Hall effects in solid-state platforms. Here, the authors predict a half-quantized mirror Hall effect in a strong topological insulator. [ABSTRACT FROM AUTHOR]

Exploring the physics coupled with layer degrees of freedom in materials has become a hot topic in quantum layertronics. We propose a robust second-order topological insulator monolayer RuOHX (X = F, Cl, and Br), a two-dimensional ferromagnetic semiconductor with large valley polarization, capable of undergoing topological phase transition induced by strain effect. In the bilayer RuOHX, we achieve layer-polarized anomalous Hall effect through interlayer sliding, originating from layer-stacking Berry curvature. Moreover, it can be controlled and reversed by the direction of ferroelectric polarization. Under appropriate biaxial strain, the bilayer RuOHX exhibits quantum layer spin Hall effect in which the helical edge states are manifested as spin-chirality-locking, due to the degeneracy of layer-polarized quantum anomalous Hall effect. Our work explores the potential application via layer-stacking topological properties for future quantum device applications. [ABSTRACT FROM AUTHOR]

Edge states in topological systems have attracted great interest due to their robustness and linear dispersions. Here a superconducting-proximitized edge interferometer is engineered on a topological insulator Ta2Pd3Te5 with asymmetric edges to realize the interfering Josephson diode effect (JDE), which hosts many advantages, such as the high efficiency as much as 73% at tiny applied magnetic fields with an ultra-low switching power around picowatt. As an important element to induce such JDE, the second-order harmonic in the current-phase relation is also experimentally confirmed by half-integer Shapiro steps. The interfering JDE is also accompanied by the antisymmetric second harmonic transport, which indicates the corresponding asymmetry in the interferometer, as well as the polarity of JDE. This edge interferometer offers an effective method to enhance the performance of JDE, and boosts great potential applications for future superconducting quantum devices. Applications of edge states are rare. Here the authors utilize asymmetric edge states in the topological material Ta2Pd3Te5 to achieve the interfering Josephson diode effect, exhibiting high efficiency with ultra-low switching power at very small magnetic fields. [ABSTRACT FROM AUTHOR]

We study the amount of backscattering of Valley-Hall modes in a classical topological insulator. In reciprocal systems, the conservation of the valley index has been argued to be at the root of the high transmission of Valley-Hall modes observed in many experimental realizations. Here, we reconsider this hypothesis by quantitatively analysing the canonical scattering problem of interface Valley-Hall modes impinging on sharp bends that may or may not conserve the valley index. We consider a tight binding model of graphene ribbons with an interface and compute the reflection and transmission coefficients using the transfer matrix formalism. We find that, in all configurations considered, the transmission of Valley-Hall modes is close to being maximal, even in cases where the valley index is not conserved. Hence, there appears to be no correlation between valley conservation and good transmission. Our results serve as a reference case for the design of Valley-Hall type metamaterial. [ABSTRACT FROM AUTHOR]

Recent advances in quantum technologies are highly influencing the current technological scenario. Hybrid devices combining superconductors and topological insulators represent an excellent opportunity to study the topological superconducting phase, which offers interesting features that might have significant implications in the development of quantum sensing and quantum computing. Furthermore, focused ion beam techniques, whose versatility enables to create sophisticated devices with high degree of customization, can enhance the creation of complex devices. Here, we develop a novel approach for creating single-crystal devices that is applied to the fabrication of superconducting devices based on topological insulator Bi2Se3 in a geometry characteristic of a superconducting quantum interference device. Characterization of these devices reveals that superconductivity is induced in our crystal and the supercurrent is modulated by applying an external magnetic field. These results open the way to tailoring the response of hybrid devices that combine superconductors and topological insulators by focused ion beam techniques. [ABSTRACT FROM AUTHOR]

Nonlinear charge transport, such as nonreciprocal longitudinal resistance and nonlinear Hall effect, has attracted considerable interest in probing the symmetries and topological properties of new materials. Recent research has revealed significant nonreciprocal longitudinal resistance and nonlinear Hall effect in MnBi2Te4, an intrinsic magnetic topological insulator, induced by the quantum metric dipole. However, the inconsistent response with charge density and conflicting C3z symmetry requirement necessitate a thorough understanding of factors affecting the nonlinear transport measurement. This study uncovers an experimental factor leading to significant nonlinear transport signals in MnBi2Te4, attributed to gate voltage oscillation from the application of large alternating current. Additionally, a methodology is proposed to suppress this effect by individually grounding the voltage electrodes during second-harmonic measurements. The investigation underscores the critical importance of assessing gate voltage oscillation's impact before determining the intrinsic nature of nonlinear transport in 2D material devices with an electrically connected operative gate electrode. [ABSTRACT FROM AUTHOR]

An interest in the study of the structural and optical properties of topological insulators, led to the selection of Bismuth telluride thin films. Among the topological insulators, Bismuth telluride is one of the promising materials that exhibit applications in the field of thermoelectric power generation. The films were prepared using the thermal evaporation method under vacuum conditions of 10−5 mbar on glass substrates maintained at a temperature of 120∘C. The thickness of the film samples ranges from 400 Å to 1400 Å. Pure phases of Bi2Te3 with a rhombohedral structure are confirmed using X-ray Diffraction. The crystallite size was calculated using Debye–Scherrer’s formula. Structural morphology and compositions are examined using SEM and EDAX. The UV–Vis study reflects the optical behavior of the thin film samples. The absorption spectra gives the direct and allowed transition band gap of the Bi2Te3 thin film samples for various thicknesses. The band gap decreases with the increase in the thickness of the Bi2Te3 thin films, suggesting that the material has significant absorption towards the visible spectrum. The Photoluminescence (PL) emissions for Bi2Te3 thin film samples of various thicknesses are examined and analysed. Raman study reveals the presence of two active modes. [ABSTRACT FROM AUTHOR]

The layered van der Waals material ZrTe5 is known as a candidate topological insulator (TI), however its topological phase and the relation with other properties such as an apparent Dirac semimetallic state is still a subject of debate. We employ a semiclassical multicarrier transport (MCT) model to analyze the magnetotransport of ZrTe5 nanodevices at hydrostatic pressures up to 2 GPa. The temperature dependence of the MCT results between 10 and 300 K is assessed in the context of thermal activation, and we obtain the positions of conduction and valence band edges in the vicinity of the chemical potential. We find evidence of the closing and re-opening of the band gap with increasing pressure, which is consistent with a phase transition from weak to strong TI. This matches expectations from ab initio band structure calculations, as well as previous observations that CVT-grown ZrTe5 is a weak TI in ambient conditions. [ABSTRACT FROM AUTHOR]

It is shown that the experimentally detected features in the low-temperature behavior of the magnetization in an external magnetic field perpendicular to the layers of manganese ions of the topological antiferromagnet MnBi2Te4 are due to quantum effects induced by the off-diagonal nature of the trigonal component of the crystal field. In this case, the anomalous increase in the magnetization of the material before the spin-flop transition, as well as after it in the phase of "collapsed" sublattices, is explained by the suppression of contributions from quantum effects. The comparison of the results of the theoretical analysis with experimental data has made it possible to refine the parameters of the effective spin model of MnBi2Te4 and to establish the important role of the noted trigonal component. [ABSTRACT FROM AUTHOR]

Previous studies have introduced topological concepts to the field of acoustics, greatly contributing to the development of acoustic wave-controlled transmission. It has evolved from acoustic wave transmission in a single frequency band to low-frequency and multiband transmission. This paper presents research on acoustic wave transmission control and the observation of transmission process properties. The paper proposes an acoustic topological insulator based on a composite resonant cavity that can change its topological boundary state and achieve controlled transmission of acoustic waves by adjusting the scatterer's rotation angle. At the same scale, this structure has a high internal space utilization and can make full use of the rotational scattering mechanism. In an air environment, the structure can create an acoustic topological transmission channel that can transmit acoustic waves in four bands. It has the advantage of having a wide frequency band. Furthermore, this study investigates the impact of channel defects on the transmission of acoustic waves, highlighting the fault-tolerant nature of these topological channels. These properties make it possible to control sound wave transmission along a predetermined path. These findings support the advancement of controllable acoustic wave transmission, which holds promise for applications in acoustic signal processing, acoustic stealth, and other related fields. [ABSTRACT FROM AUTHOR]

Pulsed solid‐state lasers comprise 2D materials as saturable absorbers that contain transparent windows of the atmosphere and characteristic fingerprint spectra of several vital molecules that are significant in various applications and research. Over the past few decades, significant progress has been made in the development of narrow pulse width, high energy, high average output power, high efficiency, and simple construction of passively Q‐switched and mode‐locked lasers with 2D materials as saturable absorbers. This review summarizes the development of 2D materials, including graphene, transition metal dichalcogenides, black phosphorus, topological insulators, and MXenes, as modulator devices for solid‐state lasers owing to their broadband operation, excellent nonlinear optical response, low recovery time, ultrafast dynamic processing, and easy fabrication. Then, some new emerging and representative applications of pulsed solid‐state lasers are introduced and illustrated such as laser surgery, material processing, and lidar. Finally, future challenges and perspectives of pulsed solid‐state lasers with 2D materials‐based saturable absorbers are analyzed and addressed. The rapid development of pulsed solid‐state lasers with the continuous improvement of modulation technology is expected to expand opportunities for application in industry, scientific, medical, and other areas. [ABSTRACT FROM AUTHOR]

Bose metals are metals made of Cooper pairs, which form at very low temperatures in superconducting films and Josephson junction arrays as an intermediate phase between superconductivity and superinsulation. We predicted the existence of this 2D metallic phase of bosons in the mid 1990s, showing that they arise due to topological quantum effects. The observation of Bose metals in perfectly regular Josephson junction arrays fully confirms our prediction and rules out alternative models based on disorder. Here, we review the basic mechanism leading to Bose metals. The key points are that the relevant vortices in granular superconductors are core-less, mobile XY vortices which can tunnel through the system due to quantum phase slips, that there is no charge-phase commutation relation preventing such vortices from being simultaneously out of condensate with charges, and that out-of-condensate charges and vortices are subject to topological mutual statistics interactions, a quantum effect that dominates at low temperatures. These repulsive mutual statistics interactions are sufficient to increase the energy of the Cooper pairs and lift them out of condensate. The result is a topological ground state in which charge conduction along edges and vortex movement across them organize themselves so as to generate the observed metallic saturation at low temperatures. This state is known today as a bosonic topological insulator. [ABSTRACT FROM AUTHOR]

In this study, first‐principles calculations are used to systematically study the structural, mechanical, and optical properties of the honeycomb AuTe monolayer, as well as the influence of layered structures on their stability and electronic properties. Additionally, the effect of alkali metal atoms decorating AuTe‐X (X = Li, Na, K) and related structural, electronic, optical, and topological insulator properties, along with the biaxial strain on the lithium‐decorated AuTe‐Li monolayer are investigated. The AuTe monolayer shows metallic characteristics, and when alkali metal atoms are decorated onto it, the resulting structures remain dynamically stable. Notably, the introduction of Li, Na, and K atoms induces bandgap opening in the decorated Li and Na monolayers near the Fermi level, causing metal‐to‐narrow bandgap semiconductor and Dirac semi‐metal transitions. Conversely, the metallic nature of the decorated AuTe‐K monolayer is retained. The emergence of a bandgap near the Fermi level, caused by alkali metal decoration, triggers a topological phase transition in AuTe‐Li, AuTe‐Na, and AuTe‐K monolayers. Optical analyses reveal that AuTe‐K decorated structure enhances light absorption in the visible spectrum. Consequently, the findings provide insights into the decoration of these two‐dimensional material monolayers, potentially advancing research and motivating the production of such monolayers for current nanodevice applications. [ABSTRACT FROM AUTHOR]

The structural, electronic, and transport properties of CaAgAs, a recently predicted topological nodal line semimetal, are investigated using density‐functional theory with spin–orbit coupling (SOC) and Boltzmann transport theory. The material exhibits a topological phase transition from a nodal line semimetal to a topological insulator (TI) phase as a result of the SOC effect. The Voigt–Reuss–Hill approximation is used to compute various mechanical properties. The calculated Seebeck coefficient ≈153.19 μV K−1, power factor ≈5.9 × 1011 W m−1 K−2 s−1, and lattice thermal conductivity ≈6.20 W m−1 K−1 suggest that CaAgAs have superior thermoelectric performance compared to other well‐known predicted thermoelectric materials. The calculated value of figure of merit for without (NSOC) is 0.34, which increases to 0.43 with SOC at 500 K. In these findings, the potential of CaAgAs is reflected as a thermoelectric material, attributed to the topological phase transition induced by SOC. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerators (TENGs) have revealed fascinating potential in multifaceted wearables. However, their reliance on physical contact and separation from human bodies presents drawbacks for efficient energy collection, especially over large areas. Herein, the first stretchable non‐contact TENG textile is proposed using a topological insulator nanocomposite coating (triboelectric layer) and a graphite‐like fabric (tribo‐charges reservoir). This design encompasses the capture, transporting, and storage of tribo‐charges, leading to enhanced device performance (452 V, 1.96 mA m−2, and 179 mW m−2) and prolonged tribo‐charges retention time (5000 min). During non‐contact operation, the output remained at 382 V (318 µA m−2), 123 V (59 µA m−2), and 94 V (23 µA m−2) for separation distances of 0.1, 0.5, and 1 cm, respectively. Additionally, it exhibits excellent stretchability (>100% strain). Notably, its performance during non‐contact operation and mechanical freedom surpasses those of previous reports, enabling both wearable non‐contact biomechanical energy harvesting and deformable self‐powered proximity sensing. Its applicability is comprehensively examined for non‐contact harvesting of body‐motion energy in garments and driving electronics. Finally, its application as a self‐powered touchless interface for system‐level applications is demonstrated. These results provide new directions for developing non‐contact biomechanical energy harvesting and sensing, enabling advancements in autonomous wearables and Metaverse applications. [ABSTRACT FROM AUTHOR]

Topologically associating domain (TAD) boundaries are the flanking edges of TADs, also known as insulated neighborhoods, within the 3D structure of genomes. A prominent feature of TAD boundaries in mammalian genomes is the enrichment of clustered CTCF sites often with mixed orientations, which can either block or facilitate enhancer–promoter (E‐P) interactions within or across distinct TADs, respectively. We will discuss recent progress in the understanding of fundamental organizing principles of the clustered CTCF insulator codes at TAD boundaries. Specifically, both inward‐ and outward‐oriented CTCF sites function as topological chromatin insulators by asymmetrically blocking improper TAD‐boundary‐crossing cohesin loop extrusion. In addition, boundary stacking and enhancer clustering facilitate long‐distance E‐P interactions across multiple TADs. Finally, we provide a unified mechanism for RNA‐mediated TAD boundary function via R‐loop formation for both insulation and facilitation. This mechanism of TAD boundary formation and insulation has interesting implications not only on how the 3D genome folds in the Euclidean nuclear space but also on how the specificity of E‐P interactions is developmentally regulated. [ABSTRACT FROM AUTHOR]

Bismuth telluride (Bi 2 Te 3) is gaining increasing attention as a material that exhibits flexo-photovoltaic effect in the infrared region, in addition to conventional thermoelectric materials and topological insulators. However, the flexo-photovoltaic effect is observed only when strains are applied to the Bi 2 Te 3 thin films by bending the substrates. To enhance the versatility of the flexo-photovoltaic effect, in this study, Bi 2 Te 3 thin films were sputtered onto a flexible substrate under a pre-curved condition, and strains were induced when the films were flattened. The crystal orientation and strains in the Bi 2 Te 3 thin films were affected by the pre-curved conditions. The Bi 2 Te 3 thin film deposited using a concave pre-curved condition exhibited an output voltage increase of approximately 15 % compared with the film deposited under a flat condition. This discovery suggests that strained Bi 2 Te 3 thin films can efficiently produce an output voltage under light irradiation without requiring a p–n junction, making them suitable for various photodetector applications. [ABSTRACT FROM AUTHOR]

It is shown that the experimentally detected features in the low-temperature behavior of the magnetization in an external magnetic field perpendicular to the layers of manganese ions of the topological antiferromagnet MnBi2Te4 are due to quantum effects induced by the off-diagonal nature of the trigonal component of the crystal field. In this case, the anomalous increase in the magnetization of the material before the spin-flop transition, as well as after it in the phase of "collapsed" sublattices, is explained by the suppression of contributions from quantum effects. The comparison of the results of the theoretical analysis with experimental data has made it possible to refine the parameters of the effective spin model of MnBi2Te4 and to establish the important role of the noted trigonal component. [ABSTRACT FROM AUTHOR]