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In the context of magnetic confinement fusion, the Megavolt ITER Injector and Concept Advancement (MITICA) project is supported by another experiment called High-Voltage Padova Test Facility (HVPTF): a device designed to improve the knowledge of high voltage holding in a vacuum. HVPTF includes a vacuum chamber containing two electrodes separated by an insulator or a vacuum gap, across which electrical discharges can develop. The electrodes are powered by two independent Cockcroft–Walton power supplies, allowing for a total voltage difference up to 800 kV. The current, voltage, and pressure inside the chamber are monitored at a sampling rate of 100 Hz. Studying the physics behind electrical discharges is fundamental to prevent their development in MITICA, where they can lead to structural damage to the experimental components. For this reason, in April 2022, a gas electron multiplier (GEM) detector was installed at HVPTF, allowing to perform X-ray measurements resolved in time, space, and energy at high rates ( ) without incurring severe pile-up problems. This work describes the analysis of data coming from current, voltage, and pressure sensors, and the X-ray GEM (XR-GEM) detector at HVPTF during two 2022 experimental campaigns. Correlations between sensor signals with the X-ray measurements have been highlighted. Experimental results indicate the presence of characteristic X-ray emissions from anode atoms during electrical discharge events in the needle–plane electrode configuration. An algorithm was developed for generating synthetic detector data based on user-defined X-ray emissions within the vacuum chamber and performing tomographic reconstructions using actual or synthetic detector data. Preliminary results indicate possible gas emissions from the anode’s surface during electrical discharge events. IEEE

© AIP Publishing LLC. The authors would like to acknowledge the CAI de Técnicas Físicas of the Universidad Complutense de Madrid for the ion implantations and metallic evaporations. This work was partially supported by the Project NUMANCIA II (Grant No. S-2009/ENE/1477) funded by the Comunidad de Madrid. Research by E. Garca-Hemme was also supported by a PICATA predoctoral fellowship of the Moncloa Campus of International Excellence (UCM-UPM). J. Olea and D. Pastor thank Professor A. Mart_ı and Professor A. Luque for useful discussions and guidance and acknowledge financial support from the MICINN within the program Juan de la Cierva (JCI-2011-10402 and JCI-2011-11471), under which this research was undertaken., We report room-temperature operation of 1 x 1 cm(2) infrared photoconductive photodetectors based on silicon supersaturated with titanium. We have fabricated these Si-based infrared photodetectors devices by means of ion implantation followed by a pulsed laser melting process. A high sub-band gap responsivity of 34 mVW(-1) has been obtained operating at the useful telecommunication applications wavelength of 1.55 mu m (0.8 eV). The sub-band gap responsivity shows a cut-off frequency as high as 1.9 kHz. These Si-based devices exhibit a non-previous reported specific detectivity of 1.7 x 10(4) cm Hz(1/2) W-1 at 660Hz, under a 1.55 mu m wavelength light. This work shows the potential of Ti supersaturated Si as a fully CMOS-compatible material for the infrared photodetection technology., Comunidad de Madrid, Moncloa Campus of International Excellence (UCM-UPM), MICINN, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2013 American Physical Society. This work was funded by MICINN (MAT2010-21156-C03-02, MAT2011-22491, and FIS2011-23230), SurMott ANR, and CNRS PICS. We are grateful to L. Patthey of the SIS beamline at the Swiss Light Source for his help during the photoemission experiments., We take advantage of complementary high-resolution experimental techniques and theoretical tools to get insight into the alpha-Sn/Ge(111) triangular lattice surface consisting of sp electrons. We report a (3 x 3) phase, characterized by a charge ordering settled by electronic correlation, which appears between the known metallic-(3 x 3) and Mott insulator phases. We identify the atomistic mechanism behind the stabilization of this phase and interpret these findings on the basis of theoretical calculations. We disentangle the role of the various degrees of freedom in the stability of the different phases found and describe the stepwise surface changes between the metallic and Mott insulating phases., MICINN, SurMott ANR, CNRS PICS, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

We report supercurrent transport measurements in hybrid Josephson junctions comprising semiconducting InAs nanowires with epitaxial ferromagnetic insulator EuS and superconducting Al coatings. The wires display a hysteretic superconducting window close to the coercivity, away from zero external magnetic field. Using a multi-interferometer setup, we measure the current-phase relation of multiple magnetic junctions and find an abrupt switch between pi and 0 phases within the superconducting window. We attribute the 0-pi transition to the discrete flipping of the EuS domains and provide a qualitative theory showing that a sizable exchange field can polarize the junction and lead to the supercurrent reversal. Both 0 and pi phases can be realized at zero external field by demagnetizing the wire.

Featured Application: The results presented in this paper highlight the chemical nature of the deposits measured on high power line insulators in Italy; the results also underline the significant role of inorganic ions in forming a conductive layer on insulators when exposed to moisture, leading to the risk of flashover events. Applications are related to the prevention of such phenomena by identifying the phase transitions of atmospheric aerosols deposited on insulators and their associated conductive effect. This is achieved through the generation of synthetic aerosols and the study of their phase transitions and conductance in an aerosol exposure chamber (AEC). The reliability of the national power grid is a key issue in modern society. Atmospheric aerosols are the main cause of the reduction in the performance of insulators and the increase in the possibility of flashovers, resulting in power line failures. Under high ambient humidity, the water-soluble compounds of atmospheric aerosols collected on the insulators’ surface can dissociate in ions and form a conductive layer, which may lead to flashover events. With a view to investigating the processes that drive these phenomena, the chemical composition of aerosol deposits on insulators in Italy was determined by ion chromatography analysis and thermos-optical and X-ray techniques. In addition, a synthetic aerosol with the same analyzed chemical composition was generated in a laboratory and deposited on PTFE filters and glass specimens allowing us to determine the deliquescence and crystallization relative humidity and the conductive effect in an aerosol exposure chamber. The results evidenced the presence of a hazardous inorganic ion layer, which generates a sharp phase transition of the aerosol deposit as a function of the ambient relative humidity; this layer poses a dangerous threat to the reliability of the power grid, increasing the probability of flashover events where the conductive layer facilitates the

© The Author(s) 2022 M. T. M. is supported by a Royal Society-Science Foundation Ireland University Research Fellowship, and acknowledges funding from the ERC Starting Grant ODYSSEY (Grant Agreement No. 758403) and the Engineering and Physical Sciences Research Council-Science Foundation Ireland Joint Funding of Research project QuamNESS. A. R. and M. A. M.-D. acknowledge financial support from the Spanish MINECO grants MINECO/FEDER Projects No. FIS2017-91460-EXP, No. PGC2018-099169-B-I00FIS-2018 and from CAM/FEDER Project No. S2018/TCS-4342 (QUITEMAD-CM) . The research of A. R. and M. A. M.-D. has been partially supported by the U.S. Army Research Office through Grant No. W911NF-14-1-0103. Calculations were performed on the GICC cluster at UCM and the Lonsdale cluster maintained by the Trinity Centre for High Performance Computing, which was funded through grants from Science Foundation Ireland., Genuinely two-dimensional robust crosscurrents-which flow against the natural direction of heat flux- have been missing since the discovery of their one-dimensional counterpart. We provide a setup to realize them on a cubic three-dimensional (3D) lattice hosting a Hofstadter model coupled to two heat baths with different temperatures. We show that these currents exhibit dissipative robustness; they are stable against the presence of impurities and tilting of the gauge field in certain nonequilibrium configurations. Moreover, we find protected boundary currents with genuinely 3D robustness, i.e., they are only stable if tunneling can occur in all three spatial directions. The model also presents generic surface currents, which are robust for both bosonic and fermionic systems. We identify the underlying qualitative mechanism responsible for the robustness of the surface currents and the crucial role played by certain discrete symmetries., Unión Europea. H2020/ERC, Ministerio de Economía y Competitividad (MINECO)/FEDER, Comunidad de Madrid/ FEDER, Engineering and Physical Sciences Research Council-Science Foundation Ireland, U.S. Army Research Office, GICC cluster at UCM, Science Foundation Ireland, Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

Rising energy and raw material prices, dwindling resources, increased recycling, and the need for sustainable management have led to growth in the smart materials sector. In recent years, the importance and diversity of bio-based adhesives for industrial applications has grown steadily. This article focuses on the production and characterization of insulation panels consisting of peat moss and two bio-based adhesives. The panels were pressed with tannin and animal-based resins and compared to panels bonded with urea formaldehyde. The physical-mechanical properties, namely, thermal conductivity (TC), water vapor diffusion resistance, modulus of rupture (MOR), modulus of elasticity (MOE), internal bond (IB), compression resistance (CR), water absorption (WA) and thickness swelling (TS) were measured and analyzed. The results show that the insulation effectiveness and mechanical stability of moss panels bound with tannin and animal glue are comparable to standard adhesives used in the composite industry.

[EN] The advent of twisted moire heterostructures as a playground for strongly correlated electron physics has led to a plethora of experimental and theoretical efforts seeking to unravel the nature of the emergent superconducting and insulating states. Among these layered compositions of two-dimensional materials, transition metal dichalcogenides are now appreciated as highly tunable platforms to simulate reinforced electronic interactions in the presence of low-energy bands with almost negligible bandwidth. Here, we focus on the twisted homobilayer WSe2 and the insulating phase at half-filling of the flat bands reported therein. More specifically, we explore the possibility of realizing quantum spin liquid (QSL) physics on the basis of a strong coupling description, including up to second-nearest neighbor Heisenberg couplings J(1) and J(2) as well as Dzyaloshinskii-Moriya (DM) interactions. Mapping out the global phase diagram as a function of an out-of-plane displacement field, we indeed find evidence for putative QSL states, albeit only close to SU(2) symmetric points. In the presence of finite DM couplings and XXZ anisotropy, long-range order is predominantly present with a mix of both commensurate and incommensurate magnetic phases.

Full Text, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), School of Environment and Sc, Science, Environment, Engineering and Technology, Wide bandgap semiconductors are currently considered as the building blocks which revolutionized many areas of nanoscience and nanotechnologies. Among them, silicon carbide has been quickly emerging as one of the most interesting materials due to its remarkable physical, chemical, mechanical, electrical properties along with its biocompatibility and its feasibility for a wafer-scale production using standard MEMS processes. Inspired by these advantages, considerable number of studies have been devoted to the development of various SiC-based electronic devices over the past years. Despite these great achievements, however, it is realized that existing sensing devices usually rely on SiC in the forms of bulk or thin film, which still exhibit relatively poor sensitivity and unstable operation due to the limitation of their surface-to-volume ratios. Another key bottleneck of these existing sensing devices lies in the impossibility to integrate SiC onto soft and stretchable substrates due to its rigid and brittle nature, which significantly hamper the broader applications of SiC in the fast-emerging field of bioelectronics. Therefore, the research activities in the framework of my Ph.D. candidature aimed to establish reliable and sustainable protocols to overcome these two critical challenges. The focuses of my research work are placed on the fabrication of SiC nanowires on SiO2 insulators and stretchable SiC microstructures integrated onto polymeric substrates with a high level of structural perfection. Towards these goals, I have successfully fabricated Si NWs on insulator by using a combination of electron beam lithography and thermal wet oxidation techniques. The temperature sensing devices based on SiC NWs exhibit a high TCR compared to their bulk counterparts. On the other hand, I successfully established an effective protocol to transfer rigid SiC microstructures onto polymeric substrates and subsequently, enhanced their stretchability by taking advantages of stru

[EN] The advent of twisted moire heterostructures as a playground for strongly correlated electron physics has led to a plethora of experimental and theoretical efforts seeking to unravel the nature of the emergent superconducting and insulating states. Among these layered compositions of two-dimensional materials, transition metal dichalcogenides are now appreciated as highly tunable platforms to simulate reinforced electronic interactions in the presence of low-energy bands with almost negligible bandwidth. Here, we focus on the twisted homobilayer WSe2 and the insulating phase at half-filling of the flat bands reported therein. More specifically, we explore the possibility of realizing quantum spin liquid (QSL) physics on the basis of a strong coupling description, including up to second-nearest neighbor Heisenberg couplings J(1) and J(2) as well as Dzyaloshinskii-Moriya (DM) interactions. Mapping out the global phase diagram as a function of an out-of-plane displacement field, we indeed find evidence for putative QSL states, albeit only close to SU(2) symmetric points. In the presence of finite DM couplings and XXZ anisotropy, long-range order is predominantly present with a mix of both commensurate and incommensurate magnetic phases.

We present results of investigations into the underlying mechanisms that drive the long observed phenomenon of contact electrification. Our experiments indicate identical single-crystal insulators are able to exchange charge at magnitudes comparable to charge transfer between dissimilar materials. Any complete theory of contact electrification must be held accountable to these observations, leading to significant constraints on possible underlying mechanisms of charge transfer between insulators. This self-charging behavior does not appear random when repeated contacts are made, suggesting the possibility of a nucleation-type event developing from seed charges. The confirmation of such a mechanism would require a probe capable of monitoring the charge distribution on the materials' surfaces without affecting the charge distribution. This effect could be direct (e.g. via polar interactions between the tip and sample or by encouraging discharges to the probe) or requiring substantial time to collect data between charging contacts, which could allow for charge redistribution or neutralization, obscuring information on the growth of charge patches.To this end, we demonstrate a novel non-destructive in-situ method of probing the charge distribution, including bipolar charging, on the surfaces of the contacting materials. This method also allows for determination of discharges and charge re-distribution during the experiment. This unprecedented understanding of charge carrier behavior immediately before and after contact provides key clues to the nature of the charge carriers in contact electrification and the underlying mechanism. These results provide constraints on both electron-dominant and ion-dominant theories of charge transfer and significantly narrows the field of possible mechanisms. Another significant aspect of this work is that it provides an explanation as to why a subject studied with so much interest for such a substantial period of time has failed to prov

This research aimed to find the process of value adding for glass wool waste from the glass wool composite board used in the vehicle industry. The waste was reprocessed to be an insulator and to determine the suitable conditions for hot-press forming to create new materials having high thermal resistant properties. Firstly, the properties of the original board; the thermal resistances (R) and the noise absorption coefficients (NRC), were measured and were found averages of 0.9055 m2K/W and 0.3955, respectively. The reprocessing conditions were varied by 2 levels; high and low, of 5 control factors; density, thickness, pressure, temperature, and surface roughness. Three repeating processes for each condition were performed. The Design of Experiment (DoE) was the full factorials; 25 experiments, by using the Analysis of Variance (ANOVA) to find main and interaction factors relating to the properties. From the ANOVA results with the ? level of significance at 0.05, it was found that the main factors responding to the high values of the thermal resistance were the thickness and density. This resulted in the suitable conditions for the hot-press process of both the new smooth and rough pads with a density of 96 kg/m3 and a thickness of 25 mm. The R values of the new insulators were in between 0.88 – 0.98 m2K/W and, additionally, the high NRC values were also provided in between 0.46 – 0.49. These findings could be applied for wall designing, wall decorations and heat shields for indoor rooms and different types of buildings.

This research aimed to find the process of value adding for glass wool waste from the glass wool composite board used in the vehicle industry. The waste was reprocessed to be an insulator and to determine the suitable conditions for hot-press forming to create new materials having high thermal resistant properties. Firstly, the properties of the original board; the thermal resistances (R) and the noise absorption coefficients (NRC), were measured and were found averages of 0.9055 m2K/W and 0.3955, respectively. The reprocessing conditions were varied by 2 levels; high and low, of 5 control factors; density, thickness, pressure, temperature, and surface roughness. Three repeating processes for each condition were performed. The Design of Experiment (DoE) was the full factorials; 25 experiments, by using the Analysis of Variance (ANOVA) to find main and interaction factors relating to the properties. From the ANOVA results with the ? level of significance at 0.05, it was found that the main factors responding to the high values of the thermal resistance were the thickness and density. This resulted in the suitable conditions for the hot-press process of both the new smooth and rough pads with a density of 96 kg/m3 and a thickness of 25 mm. The R values of the new insulators were in between 0.88 – 0.98 m2K/W and, additionally, the high NRC values were also provided in between 0.46 – 0.49. These findings could be applied for wall designing, wall decorations and heat shields for indoor rooms and different types of buildings.

Rising energy and raw material prices, dwindling resources, increased recycling, and the need for sustainable management have led to growth in the smart materials sector. In recent years, the importance and diversity of bio-based adhesives for industrial applications has grown steadily. This article focuses on the production and characterization of insulation panels consisting of peat moss and two bio-based adhesives. The panels were pressed with tannin and animal-based resins and compared to panels bonded with urea formaldehyde. The physical-mechanical properties, namely, thermal conductivity (TC), water vapor diffusion resistance, modulus of rupture (MOR), modulus of elasticity (MOE), internal bond (IB), compression resistance (CR), water absorption (WA) and thickness swelling (TS) were measured and analyzed. The results show that the insulation effectiveness and mechanical stability of moss panels bound with tannin and animal glue are comparable to standard adhesives used in the composite industry., info:eu-repo/semantics/openAccess

Rising energy and raw material prices, dwindling resources, increased recycling, and the need for sustainable management have led to growth in the smart materials sector. In recent years, the importance and diversity of bio-based adhesives for industrial applications has grown steadily. This article focuses on the production and characterization of insulation panels consisting of peat moss and two bio-based adhesives. The panels were pressed with tannin and animal-based resins and compared to panels bonded with urea formaldehyde. The physical-mechanical properties, namely, thermal conductivity (TC), water vapor diffusion resistance, modulus of rupture (MOR), modulus of elasticity (MOE), internal bond (IB), compression resistance (CR), water absorption (WA) and thickness swelling (TS) were measured and analyzed. The results show that the insulation effectiveness and mechanical stability of moss panels bound with tannin and animal glue are comparable to standard adhesives used in the composite industry., info:eu-repo/semantics/openAccess

Rising energy and raw material prices, dwindling resources, increased recycling, and the need for sustainable management have led to growth in the smart materials sector. In recent years, the importance and diversity of bio-based adhesives for industrial applications has grown steadily. This article focuses on the production and characterization of insulation panels consisting of peat moss and two bio-based adhesives. The panels were pressed with tannin and animal-based resins and compared to panels bonded with urea formaldehyde. The physical-mechanical properties, namely, thermal conductivity (TC), water vapor diffusion resistance, modulus of rupture (MOR), modulus of elasticity (MOE), internal bond (IB), compression resistance (CR), water absorption (WA) and thickness swelling (TS) were measured and analyzed. The results show that the insulation effectiveness and mechanical stability of moss panels bound with tannin and animal glue are comparable to standard adhesives used in the composite industry., info:eu-repo/semantics/openAccess

[EN] The advent of twisted moire heterostructures as a playground for strongly correlated electron physics has led to a plethora of experimental and theoretical efforts seeking to unravel the nature of the emergent superconducting and insulating states. Among these layered compositions of two-dimensional materials, transition metal dichalcogenides are now appreciated as highly tunable platforms to simulate reinforced electronic interactions in the presence of low-energy bands with almost negligible bandwidth. Here, we focus on the twisted homobilayer WSe2 and the insulating phase at half-filling of the flat bands reported therein. More specifically, we explore the possibility of realizing quantum spin liquid (QSL) physics on the basis of a strong coupling description, including up to second-nearest neighbor Heisenberg couplings J(1) and J(2) as well as Dzyaloshinskii-Moriya (DM) interactions. Mapping out the global phase diagram as a function of an out-of-plane displacement field, we indeed find evidence for putative QSL states, albeit only close to SU(2) symmetric points. In the presence of finite DM couplings and XXZ anisotropy, long-range order is predominantly present with a mix of both commensurate and incommensurate magnetic phases.

Wide bandgap semiconductors are currently considered as the building blocks which revolutionized many areas of nanoscience and nanotechnologies. Among them, silicon carbide has been quickly emerging as one of the most interesting materials due to its remarkable physical, chemical, mechanical, electrical properties along with its biocompatibility and its feasibility for a wafer-scale production using standard MEMS processes. Inspired by these advantages, considerable number of studies have been devoted to the development of various SiC-based electronic devices over the past years. Despite these great achievements, however, it is realized that existing sensing devices usually rely on SiC in the forms of bulk or thin film, which still exhibit relatively poor sensitivity and unstable operation due to the limitation of their surface-to-volume ratios. Another key bottleneck of these existing sensing devices lies in the impossibility to integrate SiC onto soft and stretchable substrates due to its rigid and brittle nature, which significantly hamper the broader applications of SiC in the fast-emerging field of bioelectronics. Therefore, the research activities in the framework of my Ph.D. candidature aimed to establish reliable and sustainable protocols to overcome these two critical challenges. The focuses of my research work are placed on the fabrication of SiC nanowires on SiO2 insulators and stretchable SiC microstructures integrated onto polymeric substrates with a high level of structural perfection. Towards these goals, I have successfully fabricated Si NWs on insulator by using a combination of electron beam lithography and thermal wet oxidation techniques. The temperature sensing devices based on SiC NWs exhibit a high TCR compared to their bulk counterparts. On the other hand, I successfully established an effective protocol to transfer rigid SiC microstructures onto polymeric substrates and subsequently, enhanced their stretchability by taking advantages of stru, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), School of Environment and Sc, Science, Environment, Engineering and Technology, Full Text

We demonstrate highly efficient control of antiferromagnetic (AFM) magnon spins by the interfacial exchange interaction in heterostructures of ferrimagnetic yttrium iron garnet (YIG) and AFM Cr2O3. At low temperatures, Cr2O3 is antiferromagnetically ordered. The interfacial exchange interaction exerted by YIG lifts the degeneracy between the AFM magnon modes in Cr2O3, resulting in a net spin polarization and a spin current dominated by left-handed magnons, even at zero magnetic field, which is detected by the spin Seebeck effect with a 5-nm-thick Pt film. In the AFM magnon-dominated region, even if the magnetic field is not sufficiently strong to induce the spin-flop transition in Cr2O3, the total spin Seebeck signal polarity flips when the YIG magnetization switches. It clearly indicates that the Cr2O3 magnon polarization is controlled by YIG magnetization through the interfacial exchange interaction. The demonstration of the efficient control of AFM magnon polarization opens a pathway to manipulate AFM magnon quantum states using FM-AFM heterostructures.

Transformers play an essential role in power networks, ensuring that generated power gets to consumers at the safest voltage level. However, they are prone to insulation failure from ageing, which has fatal and economic consequences if left undetected or unattended. Traditional detection methods are based on scheduled maintenance practices that often involve taking samples from in situ transformers and analysing them in laboratories using several techniques. This conventional method exposes the engineer performing the test to hazards, requires specialised training, and does not guarantee reliable results because samples can be contaminated during collection and transportation. This paper reviews the transformer oil types and some traditional ageing detection methods, including breakdown voltage (BDV), spectroscopy, dissolved gas analysis, total acid number, interfacial tension, and corresponding regulating standards. In addition, a review of sensors, technologies to improve the reliability of online ageing detection, and related online transformer ageing systems is covered in this work. A non-destructive online ageing detection method for in situ transformer oil is a better alternative to the traditional offline detection method. Moreover, when combined with the Internet of Things (IoT) and artificial intelligence, a prescriptive maintenance solution emerges, offering more advantages and robustness than offline preventive maintenance approaches.

[EN]Recently, the twist angle between adjacent sheets of stacked van der Waals materials emerged as a new knob to engineer correlated states of matter in two-dimensional heterostructures in a controlled manner, giving rise to emergent phenomena such as superconductivity or correlated insulating states. Here, we use an ab initio based approach to characterize the electronic properties of twisted bilayer MoS2. We report that, in marked contrast to twisted bilayer graphene, slightly hole-doped MoS2 realizes a strongly asymmetric p(x)-p(y) Hubbard model on the honeycomb lattice, with two almost entirely dispersionless bands emerging due to destructive interference. The origin of these dispersionless bands, is similar to that of the flat bands in the prototypical Lieb or Kagome lattices and co-exists with the general band flattening at small twist angle due to the moire interference. We study the collective behavior of twisted bilayer MoS2 in the presence of interactions, and characterize an array of different magnetic and orbitally-ordered correlated phases, which may be susceptible to quantum fluctuations giving rise to exotic, purely quantum, states of matter. Twisted van der Waals systems are known to host flat electronic bands, originating from moire potential. Here, the authors predict from purely geometric considerations a new type of nearly dispersionless bands in twisted bilayer MoS2, resulting from destructive interference between effective lattice hopping matrix elements.

Twisting two adjacent layers of van der Waals materials with respect to each other can lead to flat two-dimensional electronic bands which enables a wealth of physical phenomena. Here, we generalize this concept of so-called moire flat bands to engineer flat bands in all three spatial dimensions controlled by the twist angle. The basic concept is to stack the material such that the large spatial moire interference patterns are spatially shifted from one twisted layer to the next. We exemplify the general concept by considering graphitic systems, boron nitride, and WSe2, but the approach is applicable to any two-dimensional van der Waals material. For hexagonal boron nitride, we develop an ab initio fitted tight binding model that captures the corresponding three-dimensional low-energy electronic structure. We outline that interesting three-dimensional correlated phases of matter can be induced and controlled following this route, including quantum magnets and unconventional superconducting states.

Atomically thin van der Waals materials stacked with an interlayer twist have proven to be an excellent platform toward achieving gate-tunable correlated phenomena linked to the formation of flat electronic bands. In this work we demonstrate the formation of emergent correlated phases in multilayer rhombohedral graphene-a simple material that also exhibits a flat electronic band edge but without the need of having a moire superlattice induced by twisted van der Waals layers. We show that two layers of bilayer graphene that are twisted by an arbitrary tiny angle host large (micrometer-scale) regions of uniform rhombohedral four-layer (ABCA) graphene that can be independently studied. Scanning tunneling spectroscopy reveals that ABCA graphene hosts an unprecedentedly sharp van Hove singularity of 3-5-meV half-width. We demonstrate that when this van Hove singularity straddles the Fermi level, a correlated many-body gap emerges with peak-to-peak value of 9.5 meV at charge neutrality. Mean-field theoretical calculations for model with short-ranged interactions indicate that two primary candidates for the appearance of this broken symmetry state are a charge-transfer excitonic insulator and a ferrimagnet. Finally, we show that ABCA graphene hosts surface topological helical edge states at natural interfaces with ABAB graphene which can be turned on and off with gate voltage, implying that small-angle twisted double-bilayer graphene is an ideal programmable topological quantum material

U fokusu ovog rada je koncept insulatora u teoriji regionalnog bezbednosnog kompleksa (TRBK), kao originalnog doprinosa Buzana i Vejvera studijama bezbednosti. Uvođenje koncepta insulatora bilo je neophodno kako bi se prevazišla teškoća u određivanju granica između regiona, odnosno kompleksa, odnosno kako bi se objasnilo različito delovanje jedinica (pre svega država) u odnosu na regionalni bezbednosni kompleks kojem ne pripadaju. Cilj ovog rada je propitivanje i dalja nadgradnja koncepta insulatora u TRBK, uvođenjem razlikovanja pasivnog i aktivnog insulatora. Pasivni insulator u ovakvoj podeli predstavlja tradicionalnog, odnosno uobičajenog insulatora koji razdvaja bezbednosne dinamike okolnih kompleksa, apsorbujući njihove energije. Za razliku od njega, aktivni insulator je onaj koji više emituje energiju, koji je važan činilac u bezbednosnim dinamikama susednih kompleksa, ali ne u dovoljnoj meri da ih ujedini u jedan jedinstveni. Pored doprinosa daljem razvijanju i preciziranju pojmovno-kategorijalnog aparata TRBK, uvođenje ovakve dihotomije ima i analitičko-prediktivnu funkciju jer postojanje aktivnog inuslatora sugeriše moguću transformaciju kompleksa, odnosno ukazuje na potencijal za integraciju ili dezintegraciju određenih (pod)regiona. Koncept insulatora se u radu težišno propituje razmatranjem statusa Turske u TRBK, dok se predložena klasifikacija insulatora inicijalno testira i kroz skiciranje primene na druge države koje su Buzan i Vejver klasifikovali kao insulatore.

Atomically thin van der Waals materials stacked with an interlayer twist have proven to be an excellent platform toward achieving gate-tunable correlated phenomena linked to the formation of flat electronic bands. In this work we demonstrate the formation of emergent correlated phases in multilayer rhombohedral graphene-a simple material that also exhibits a flat electronic band edge but without the need of having a moire superlattice induced by twisted van der Waals layers. We show that two layers of bilayer graphene that are twisted by an arbitrary tiny angle host large (micrometer-scale) regions of uniform rhombohedral four-layer (ABCA) graphene that can be independently studied. Scanning tunneling spectroscopy reveals that ABCA graphene hosts an unprecedentedly sharp van Hove singularity of 3-5-meV half-width. We demonstrate that when this van Hove singularity straddles the Fermi level, a correlated many-body gap emerges with peak-to-peak value of 9.5 meV at charge neutrality. Mean-field theoretical calculations for model with short-ranged interactions indicate that two primary candidates for the appearance of this broken symmetry state are a charge-transfer excitonic insulator and a ferrimagnet. Finally, we show that ABCA graphene hosts surface topological helical edge states at natural interfaces with ABAB graphene which can be turned on and off with gate voltage, implying that small-angle twisted double-bilayer graphene is an ideal programmable topological quantum material

[EN]Recently, the twist angle between adjacent sheets of stacked van der Waals materials emerged as a new knob to engineer correlated states of matter in two-dimensional heterostructures in a controlled manner, giving rise to emergent phenomena such as superconductivity or correlated insulating states. Here, we use an ab initio based approach to characterize the electronic properties of twisted bilayer MoS2. We report that, in marked contrast to twisted bilayer graphene, slightly hole-doped MoS2 realizes a strongly asymmetric p(x)-p(y) Hubbard model on the honeycomb lattice, with two almost entirely dispersionless bands emerging due to destructive interference. The origin of these dispersionless bands, is similar to that of the flat bands in the prototypical Lieb or Kagome lattices and co-exists with the general band flattening at small twist angle due to the moire interference. We study the collective behavior of twisted bilayer MoS2 in the presence of interactions, and characterize an array of different magnetic and orbitally-ordered correlated phases, which may be susceptible to quantum fluctuations giving rise to exotic, purely quantum, states of matter. Twisted van der Waals systems are known to host flat electronic bands, originating from moire potential. Here, the authors predict from purely geometric considerations a new type of nearly dispersionless bands in twisted bilayer MoS2, resulting from destructive interference between effective lattice hopping matrix elements.

Twisting two adjacent layers of van der Waals materials with respect to each other can lead to flat two-dimensional electronic bands which enables a wealth of physical phenomena. Here, we generalize this concept of so-called moire flat bands to engineer flat bands in all three spatial dimensions controlled by the twist angle. The basic concept is to stack the material such that the large spatial moire interference patterns are spatially shifted from one twisted layer to the next. We exemplify the general concept by considering graphitic systems, boron nitride, and WSe2, but the approach is applicable to any two-dimensional van der Waals material. For hexagonal boron nitride, we develop an ab initio fitted tight binding model that captures the corresponding three-dimensional low-energy electronic structure. We outline that interesting three-dimensional correlated phases of matter can be induced and controlled following this route, including quantum magnets and unconventional superconducting states.

U fokusu ovog rada je koncept insulatora u teoriji regionalnog bezbednosnog kompleksa (TRBK), kao originalnog doprinosa Buzana i Vejvera studijama bezbednosti. Uvođenje koncepta insulatora bilo je neophodno kako bi se prevazišla teškoća u određivanju granica između regiona, odnosno kompleksa, odnosno kako bi se objasnilo različito delovanje jedinica (pre svega država) u odnosu na regionalni bezbednosni kompleks kojem ne pripadaju. Cilj ovog rada je propitivanje i dalja nadgradnja koncepta insulatora u TRBK, uvođenjem razlikovanja pasivnog i aktivnog insulatora. Pasivni insulator u ovakvoj podeli predstavlja tradicionalnog, odnosno uobičajenog insulatora koji razdvaja bezbednosne dinamike okolnih kompleksa, apsorbujući njihove energije. Za razliku od njega, aktivni insulator je onaj koji više emituje energiju, koji je važan činilac u bezbednosnim dinamikama susednih kompleksa, ali ne u dovoljnoj meri da ih ujedini u jedan jedinstveni. Pored doprinosa daljem razvijanju i preciziranju pojmovno-kategorijalnog aparata TRBK, uvođenje ovakve dihotomije ima i analitičko-prediktivnu funkciju jer postojanje aktivnog inuslatora sugeriše moguću transformaciju kompleksa, odnosno ukazuje na potencijal za integraciju ili dezintegraciju određenih (pod)regiona. Koncept insulatora se u radu težišno propituje razmatranjem statusa Turske u TRBK, dok se predložena klasifikacija insulatora inicijalno testira i kroz skiciranje primene na druge države koje su Buzan i Vejver klasifikovali kao insulatore.

The transition from insulator to conductor can be realized in some materials but requires modification of both the arrangement of atoms and their electronic configurations. This is often achieved by doping. Here we reveal a different mechanism the lattice may adopt to induce such a transition. Experiments showed the surprising finding that limited exposure to sub-bandgap light caused a permanent transition from an insulator state to a conductor state in the insulating oxide Ga2O3, with 9-orders of magnitude increase in electronic conduction. Furthermore, annealing up to 400 C did not suppress or decrease the induced conductivity. Photoexcitation by light-induced modification in the charge state of defects and subsequent lattice distortion around them was suggested to be the underlying mechanism behind this transition. Density functional theory calculations confirmed that modifying the charge state of defects leads to redistribution of the localized electrons and massive structural distortion in the surrounding lattice, causing large shifts in the density of states and introducing new states with shallower energy levels. Both experimental and theoretical results revealed the introduction of new stable shallow energy levels, explaining the mechanism behind the transition from an insulator to a conductor state by light. We suggest that this mechanism may occur in other wide bandgap metal oxides leading to drastic modification in their electronic properties.

Atomically thin van der Waals materials stacked with an interlayer twist have proven to be an excellent platform toward achieving gate-tunable correlated phenomena linked to the formation of flat electronic bands. In this work we demonstrate the formation of emergent correlated phases in multilayer rhombohedral graphene-a simple material that also exhibits a flat electronic band edge but without the need of having a moire superlattice induced by twisted van der Waals layers. We show that two layers of bilayer graphene that are twisted by an arbitrary tiny angle host large (micrometer-scale) regions of uniform rhombohedral four-layer (ABCA) graphene that can be independently studied. Scanning tunneling spectroscopy reveals that ABCA graphene hosts an unprecedentedly sharp van Hove singularity of 3-5-meV half-width. We demonstrate that when this van Hove singularity straddles the Fermi level, a correlated many-body gap emerges with peak-to-peak value of 9.5 meV at charge neutrality. Mean-field theoretical calculations for model with short-ranged interactions indicate that two primary candidates for the appearance of this broken symmetry state are a charge-transfer excitonic insulator and a ferrimagnet. Finally, we show that ABCA graphene hosts surface topological helical edge states at natural interfaces with ABAB graphene which can be turned on and off with gate voltage, implying that small-angle twisted double-bilayer graphene is an ideal programmable topological quantum material

[EN]Recently, the twist angle between adjacent sheets of stacked van der Waals materials emerged as a new knob to engineer correlated states of matter in two-dimensional heterostructures in a controlled manner, giving rise to emergent phenomena such as superconductivity or correlated insulating states. Here, we use an ab initio based approach to characterize the electronic properties of twisted bilayer MoS2. We report that, in marked contrast to twisted bilayer graphene, slightly hole-doped MoS2 realizes a strongly asymmetric p(x)-p(y) Hubbard model on the honeycomb lattice, with two almost entirely dispersionless bands emerging due to destructive interference. The origin of these dispersionless bands, is similar to that of the flat bands in the prototypical Lieb or Kagome lattices and co-exists with the general band flattening at small twist angle due to the moire interference. We study the collective behavior of twisted bilayer MoS2 in the presence of interactions, and characterize an array of different magnetic and orbitally-ordered correlated phases, which may be susceptible to quantum fluctuations giving rise to exotic, purely quantum, states of matter. Twisted van der Waals systems are known to host flat electronic bands, originating from moire potential. Here, the authors predict from purely geometric considerations a new type of nearly dispersionless bands in twisted bilayer MoS2, resulting from destructive interference between effective lattice hopping matrix elements.

Twisting two adjacent layers of van der Waals materials with respect to each other can lead to flat two-dimensional electronic bands which enables a wealth of physical phenomena. Here, we generalize this concept of so-called moire flat bands to engineer flat bands in all three spatial dimensions controlled by the twist angle. The basic concept is to stack the material such that the large spatial moire interference patterns are spatially shifted from one twisted layer to the next. We exemplify the general concept by considering graphitic systems, boron nitride, and WSe2, but the approach is applicable to any two-dimensional van der Waals material. For hexagonal boron nitride, we develop an ab initio fitted tight binding model that captures the corresponding three-dimensional low-energy electronic structure. We outline that interesting three-dimensional correlated phases of matter can be induced and controlled following this route, including quantum magnets and unconventional superconducting states.

U fokusu ovog rada je koncept insulatora u teoriji regionalnog bezbednosnog kompleksa (TRBK), kao originalnog doprinosa Buzana i Vejvera studijama bezbednosti. Uvođenje koncepta insulatora bilo je neophodno kako bi se prevazišla teškoća u određivanju granica između regiona, odnosno kompleksa, odnosno kako bi se objasnilo različito delovanje jedinica (pre svega država) u odnosu na regionalni bezbednosni kompleks kojem ne pripadaju. Cilj ovog rada je propitivanje i dalja nadgradnja koncepta insulatora u TRBK, uvođenjem razlikovanja pasivnog i aktivnog insulatora. Pasivni insulator u ovakvoj podeli predstavlja tradicionalnog, odnosno uobičajenog insulatora koji razdvaja bezbednosne dinamike okolnih kompleksa, apsorbujući njihove energije. Za razliku od njega, aktivni insulator je onaj koji više emituje energiju, koji je važan činilac u bezbednosnim dinamikama susednih kompleksa, ali ne u dovoljnoj meri da ih ujedini u jedan jedinstveni. Pored doprinosa daljem razvijanju i preciziranju pojmovno-kategorijalnog aparata TRBK, uvođenje ovakve dihotomije ima i analitičko-prediktivnu funkciju jer postojanje aktivnog inuslatora sugeriše moguću transformaciju kompleksa, odnosno ukazuje na potencijal za integraciju ili dezintegraciju određenih (pod)regiona. Koncept insulatora se u radu težišno propituje razmatranjem statusa Turske u TRBK, dok se predložena klasifikacija insulatora inicijalno testira i kroz skiciranje primene na druge države koje su Buzan i Vejver klasifikovali kao insulatore.

We investigate a class of two-dimensional two-band microscopic models in which the inter-band repulsive interactions play the dominant role. We first demonstrate three different schemes of constraining the ratios between the three types of inter-band interactions - density-density, spin exchange, and pair-hopping that render the model free of the fermionic sign-problem for any filling and, consequently, amenable to efficient Quantum Monte Carlo simulations. We then study the behavior of these signproblem-free models in the strong-coupling regime. In the cases where spin-rotational invariance is preserved or lowered to a planar symmetry, the strong-coupling ground state is a quantum paramagnet. However, in the case where there is only a residual Ising symmetry, the strong-coupling expansion maps onto the transverse-field J(1)-J(2) Ising model, whose pseudospins are associated with local inter-band magnetic order. We show that by varying the band structure parameters within a reasonable range of values, a variety of ground states and quantum critical points can be accessed in the strong-coupling regime, some of which are not realized in the weak-coupling regime. We compare these results with the case of the single-band Hubbard model, where only intra-band repulsion is present, and whose strong-coupling behavior is captured by a simple Heisenberg model. (C) 2021 Elsevier Inc. All rights reserved.

The nonequilibrium regime provides an exciting frontier in the search for novel quantum phases of matter. Here, the authors show that optically driving a lightly-doped semiconductor can lead to the spontaneous formation of a dynamical quantum liquid crystalline phase with a rotating magnetization.Floquet engineering uses coherent time-periodic drives to realize designer band structures on-demand, thus yielding a versatile approach for inducing a wide range of exotic quantum many-body phenomena. Here we show how this approach can be used to induce non-equilibrium correlated states with spontaneously broken symmetry in lightly doped semiconductors. In the presence of a resonant driving field, the system spontaneously develops quantum liquid crystalline order featuring strong anisotropy whose directionality rotates as a function of time. The phase transition occurs in the steady state of the system achieved due to the interplay between the coherent external drive, electron-electron interactions, and dissipative processes arising from the coupling to phonons and the electromagnetic environment. We obtain the phase diagram of the system using numerical calculations that match predictions obtained from a phenomenological treatment and discuss the conditions on the system and the external drive under which spontaneous symmetry breaking occurs. Our results demonstrate that coherent driving can be used to induce non-equilibrium quantum phases of matter with dynamical broken symmetry.

In recent years, the notion of 'Quantum Materials' has emerged as a powerful unifying concept across diverse fields of science and engineering, from condensed-matter and coldatom physics to materials science and quantum computing. Beyond traditional quantum materials such as unconventional superconductors, heavy fermions, and multiferroics, the field has significantly expanded to encompass topological quantum matter, two-dimensional materials and their van der Waals heterostructures, Moire materials, Floquet time crystals, as well as materials and devices for quantum computation with Majorana fermions. In this Roadmap collection we aim to capture a snapshot of the most recent developments in the field, and to identify outstanding challenges and emerging opportunities. The format of the Roadmap, whereby experts in each discipline share their viewpoint and articulate their vision for quantum materials, reflects the dynamic and multifaceted nature of this research area, and is meant to encourage exchanges and discussions across traditional disciplinary boundaries. It is our hope that this collective vision will contribute to sparking new fascinating questions and activities at the intersection of materials science, condensed matter physics, device engineering, and quantum information, and to shaping a clearer landscape of quantum materials science as a new frontier of interdisciplinary scientific inquiry. We stress that this article is not meant to be a fully comprehensive review but rather an up-to-date snapshot of different areas of research on quantum materials with a minimal number of references focusing on the latest developments.

The nonequilibrium regime provides an exciting frontier in the search for novel quantum phases of matter. Here, the authors show that optically driving a lightly-doped semiconductor can lead to the spontaneous formation of a dynamical quantum liquid crystalline phase with a rotating magnetization.Floquet engineering uses coherent time-periodic drives to realize designer band structures on-demand, thus yielding a versatile approach for inducing a wide range of exotic quantum many-body phenomena. Here we show how this approach can be used to induce non-equilibrium correlated states with spontaneously broken symmetry in lightly doped semiconductors. In the presence of a resonant driving field, the system spontaneously develops quantum liquid crystalline order featuring strong anisotropy whose directionality rotates as a function of time. The phase transition occurs in the steady state of the system achieved due to the interplay between the coherent external drive, electron-electron interactions, and dissipative processes arising from the coupling to phonons and the electromagnetic environment. We obtain the phase diagram of the system using numerical calculations that match predictions obtained from a phenomenological treatment and discuss the conditions on the system and the external drive under which spontaneous symmetry breaking occurs. Our results demonstrate that coherent driving can be used to induce non-equilibrium quantum phases of matter with dynamical broken symmetry.

In recent years, the notion of 'Quantum Materials' has emerged as a powerful unifying concept across diverse fields of science and engineering, from condensed-matter and coldatom physics to materials science and quantum computing. Beyond traditional quantum materials such as unconventional superconductors, heavy fermions, and multiferroics, the field has significantly expanded to encompass topological quantum matter, two-dimensional materials and their van der Waals heterostructures, Moire materials, Floquet time crystals, as well as materials and devices for quantum computation with Majorana fermions. In this Roadmap collection we aim to capture a snapshot of the most recent developments in the field, and to identify outstanding challenges and emerging opportunities. The format of the Roadmap, whereby experts in each discipline share their viewpoint and articulate their vision for quantum materials, reflects the dynamic and multifaceted nature of this research area, and is meant to encourage exchanges and discussions across traditional disciplinary boundaries. It is our hope that this collective vision will contribute to sparking new fascinating questions and activities at the intersection of materials science, condensed matter physics, device engineering, and quantum information, and to shaping a clearer landscape of quantum materials science as a new frontier of interdisciplinary scientific inquiry. We stress that this article is not meant to be a fully comprehensive review but rather an up-to-date snapshot of different areas of research on quantum materials with a minimal number of references focusing on the latest developments.

Several distinct activities and functions have been described for chromatin insulators, which separate genes along chromosomes into functional units. Here, we describe a novel mechanism of functional separation whereby an insulator prevents gene repression. When the homie insulator is deleted from the end of a Drosophila even skipped (eve) locus, a flanking P-element promoter is activated in a partial eve pattern, causing expression driven by enhancers in the 3' region to be repressed. The mechanism involves transcriptional read-through from the flanking promoter. This conclusion is based on the following. Read-through driven by a heterologous enhancer is sufficient to repress, even when homie is in place. Furthermore, when the flanking promoter is turned around, repression is minimal. Transcriptional read-through that does not produce anti-sense RNA can still repress expression, ruling out RNAi as the mechanism in this case. Thus, transcriptional interference, caused by enhancer capture and read-through when the insulator is removed, represses eve promoter-driven expression. We also show that enhancer-promoter specificity and processivity of transcription can have decisive effects on the consequences of insulator removal. First, a core heat shock 70 promoter that is not activated well by eve enhancers did not cause read-through sufficient to repress the eve promoter. Second, these transcripts are less processive than those initiated at the P-promoter, measured by how far they extend through the eve locus, and so are less disruptive. These results highlight the importance of considering transcriptional read-through when assessing the effects of insulators on gene expression.

Deterioration of cable insulator can be caused by many factors such as aging, fault and breakdown. These factors are caused by the presence of moisture, impurities and heat due to high temperatures in an insulator. The maintenance and replacement for insulation system in power cables, power transformers and electric machine stator are generally expensive and time consuming. Thus, the performance and ability of an insulator can be monitored through polarization and depolarization current (PDC). Polarization and depolarization current (PDC) is a non-destructive test method that is used to analyse many factors that affects the behaviour of an insulator in time domain. This paper presents the review on application of polarization and depolarization current test method on different type of insulator. The factors that affects the performance of different type of insulator will be discussed in this paper. Moreover, the theory of polarization and depolarization current will be explained in order to understand the behaviour of polarization and depolarization current curve when fault occurs. Last but not least, this paper will provide a review on the different type of factors that affects the performance of different types of insulation.

The stationary behavior of a quantum system is determined by its Hamiltonian and its boundary conditions. All quantum phase transitions (QPT) reported previously were induced by changing the Hamiltonian. In a circular spin model with Heisenberg XY interactions and no magnetic field, we observe an anomaly in quantum phases caused by a qualitative change of the boundary condition. The unexpected anomaly features an infinite number of single-particle levels, in the same pattern as the single-photon-triggered quantum phase transition in the Rabi model.

Experimental advances in the fabrication and characterization of few-layer materials stacked at a relative twist of small angle have recently shown the emergence of flat energy bands. As a consequence electron interactions become relevant, providing inroads into the physics of strongly correlated two-dimensional systems. Here, we demonstrate by combining large scale ab initio simulations with numerically exact strong correlation approaches that an effective one-dimensional system emerges upon stacking two twisted sheets of GeSe, in marked contrast to all moire systems studied so far. This not only allows to study the necessarily collective nature of excitations in one dimension, but can also serve as a promising platform to scrutinize the crossover from two to one dimension in a controlled setup by varying the twist angle, which provides an intriguing benchmark with respect to theory. We thus establish twisted bilayer GeSe as an intriguing inroad into the strongly correlated physics of lowdimensional systems. Twisting the relative orientation of the sheets in few-layer van der Waals materials can cause drastic changes in the electronic bandstructure. Here, the authors predict that twisted bilayer GeSe realises an effective one-dimensional flat-band electronic system with exotic, strongly correlated behaviour.

This project was a step forward in investigating the effect of supply voltage harmonic contents on the measured leakage current of polluted insulators operating in different environments. This study was then used as a basis for developing a sound theoretical understanding of the effects of supply voltage harmonic contents on the measured leakage current characteristics. This study was also used to develop a new condition monitoring index for the polluted insulator under harmonically distorted supply voltage.

The stationary behavior of a quantum system is determined by its Hamiltonian and its boundary conditions. All quantum phase transitions (QPT) reported previously were induced by changing the Hamiltonian. In a circular spin model with Heisenberg XY interactions and no magnetic field, we observe an anomaly in quantum phases caused by a qualitative change of the boundary condition. The unexpected anomaly features an infinite number of single-particle levels, in the same pattern as the single-photon-triggered quantum phase transition in the Rabi model.

Experimental advances in the fabrication and characterization of few-layer materials stacked at a relative twist of small angle have recently shown the emergence of flat energy bands. As a consequence electron interactions become relevant, providing inroads into the physics of strongly correlated two-dimensional systems. Here, we demonstrate by combining large scale ab initio simulations with numerically exact strong correlation approaches that an effective one-dimensional system emerges upon stacking two twisted sheets of GeSe, in marked contrast to all moire systems studied so far. This not only allows to study the necessarily collective nature of excitations in one dimension, but can also serve as a promising platform to scrutinize the crossover from two to one dimension in a controlled setup by varying the twist angle, which provides an intriguing benchmark with respect to theory. We thus establish twisted bilayer GeSe as an intriguing inroad into the strongly correlated physics of lowdimensional systems. Twisting the relative orientation of the sheets in few-layer van der Waals materials can cause drastic changes in the electronic bandstructure. Here, the authors predict that twisted bilayer GeSe realises an effective one-dimensional flat-band electronic system with exotic, strongly correlated behaviour.

En el vídeo se explican las partes de un cable aislado de los que se usan en líneas de alta tensión. Se muestra un caso real seccionado y se explican algunos aspectos de interés.

En el vídeo se explican las partes de un cable aislado de los que se usan en líneas de alta tensión. Se muestra un caso real seccionado y se explican algunos aspectos de interés.

Experimental advances in the fabrication and characterization of few-layer materials stacked at a relative twist of small angle have recently shown the emergence of flat energy bands. As a consequence electron interactions become relevant, providing inroads into the physics of strongly correlated two-dimensional systems. Here, we demonstrate by combining large scale ab initio simulations with numerically exact strong correlation approaches that an effective one-dimensional system emerges upon stacking two twisted sheets of GeSe, in marked contrast to all moire systems studied so far. This not only allows to study the necessarily collective nature of excitations in one dimension, but can also serve as a promising platform to scrutinize the crossover from two to one dimension in a controlled setup by varying the twist angle, which provides an intriguing benchmark with respect to theory. We thus establish twisted bilayer GeSe as an intriguing inroad into the strongly correlated physics of lowdimensional systems. Twisting the relative orientation of the sheets in few-layer van der Waals materials can cause drastic changes in the electronic bandstructure. Here, the authors predict that twisted bilayer GeSe realises an effective one-dimensional flat-band electronic system with exotic, strongly correlated behaviour.

The stationary behavior of a quantum system is determined by its Hamiltonian and its boundary conditions. All quantum phase transitions (QPT) reported previously were induced by changing the Hamiltonian. In a circular spin model with Heisenberg XY interactions and no magnetic field, we observe an anomaly in quantum phases caused by a qualitative change of the boundary condition. The unexpected anomaly features an infinite number of single-particle levels, in the same pattern as the single-photon-triggered quantum phase transition in the Rabi model.

Deterioration of cable insulator can be caused by many factors such as aging, fault and breakdown. These factors are caused by the presence of moisture, impurities and heat due to high temperatures in an insulator. The maintenance and replacement for insulation system in power cables, power transformers and electric machine stator are generally expensive and time consuming. Thus, the performance and ability of an insulator can be monitored through polarization and depolarization current (PDC). Polarization and depolarization current (PDC) is a non-destructive test method that is used to analyse many factors that affects the behaviour of an insulator in time domain. This paper presents the review on application of polarization and depolarization current test method on different type of insulator. The factors that affects the performance of different type of insulator will be discussed in this paper. Moreover, the theory of polarization and depolarization current will be explained in order to understand the behaviour of polarization and depolarization current curve when fault occurs. Last but not least, this paper will provide a review on the different type of factors that affects the performance of different types of insulation.