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In metals, electrons in a magnetic field undergo cyclotron motion, leading to oscillations in physical properties called quantum oscillations. This phenomenon has never been seen in a robust insulator because there are no mobile electrons. We report an exception to this rule. We study a Mott insulator on a kagome lattice which does not order magnetically down to milli-Kelvin temperatures despite antiferromagnetic interactions. We observe a plateau at magnetization equal to 1/9 Bohr magneton per magnetic ion, accompanied by oscillations in the magnetic torque, reminiscent of quantum oscillations in metals. The temperature dependence obeys Fermi distribution. These phenomena are consistent with a quantum spin liquid state whose excitations are fermionic spinons with a Dirac-like spectrum coupled to an emergent gauge field. [ABSTRACT FROM AUTHOR]

We evaluate the Hall coefficient characterising magnetotransport in an intercalated graphite CaC 6 with the Fermi surface reconstructed by an uniaxial charge density wave from closed pockets to open sheets. As the typical order parameter, corresponding to the pseudo-gap in electronic spectrum and consequently to spacing between electron trajectories in reciprocal space, is of the order of 10 2 K, magnetic breakdown in strong experimentally achievable fields of the order of 10T is inevitable. The classical expressions for the components of the magnetoconductivity tensor are strongly modified by magnetic field-assisted over-gap tunneling causing quantum interference. Due to magnetic breakdown, all magnetoconductivity components undergo strong quantum oscillations reflected in the Hall coefficient. In their nature, these are different than standard Shubnikov de Haas oscillations which would not appear in a system with an open Fermi surface. [ABSTRACT FROM AUTHOR]

A long-standing problem in the study of the under-hole-doped cuprates has been the description of the Fermi surfaces underlying the high magnetic field quantum oscillations, and their connection to the higher temperature pseudogap metal. Harrison and Sebastian [Phys. Rev. Lett. 106, 226402 (2011)] proposed that the pseudogap "Fermi arcs" are reconstructed into an electron pocket by field-induced charge density wave order. But computations on such a model [Zhang and Mei, Europhys. Lett. 114, 47008 (2016)] show an unobserved additional oscillation frequency from a Fermi surface arising from the backsides of the hole pockets completing the Fermi arcs. We describe a transition from a fractionalized Fermi liquid (FL*) model of the pseudogap metal, to a metal with bidirectional charge density wave order without fractionalization. We show that the confinement of the fermionic spinon excitations of the FL* across this transition can eliminate the unobserved oscillation frequency. [ABSTRACT FROM AUTHOR]

The Mott-Ioffe-Regel limit sets the lower bound of the carrier mean free path for coherent quasiparticle transport. Metallicity beyond this limit is of great interest because it is often closely related to quantum criticality and unconventional superconductivity. Progress along this direction mainly focuses on the strange-metal behaviors originating from the evolution of the quasiparticle scattering rate, such as linear-in-temperature resistivity, while the quasiparticle coherence phenomena in this regime are much less explored due to the short mean free path at the diffusive bound. Here we report the observation of quantum oscillations from Landau quantization near the Mott-Ioffe-Regel limit in CaAs3. Despite the insulator-like temperature dependence of resistivity, CaAs3 presents giant magnetoresistance and prominent Shubnikov–de Haas oscillations from Fermi surfaces, indicating highly coherent band transport. In contrast, quantum oscillation is absent in the magnetic torque. The quasiparticle effective mass increases systematically with magnetic fields, manifesting a much larger value than what is expected based on magneto-infrared spectroscopy. This suggests a strong many-body renormalization effect near the Fermi surface. We find that these unconventional behaviors may be explained by the interplay between the mobility edge and the van Hove singularity, which results in the formation of coherent cyclotron orbits emerging at the diffusive bound. Our results call for further study on the electron correlation effect of the van Hove singularity. [ABSTRACT FROM AUTHOR]

Owing to their consistently emerging applications in modern photonics, highly sensitive and rapid mid‐infrared (MIR) photodetectors, operating at high temperatures, are of great significance. Herein, a novel PbTe/Ge heterostructure is introduced. Notably, the discovery of a 2D electron gas (2DEG) system on the surface of the PbTe layer is experimentally identified for the first time. A high‐performance PbTe/Ge heterostructure MIR photodetector utilizing a plasmonic photovoltaic effect is developed by employing asymmetric electrodes. The photodetecting device demonstrates an exceptionally high detectivity of 1.1 × 1011 Jones along with a short response time of 15 ns at room temperature. Additionally, the proposed plasmonic photovoltaic mechanism of the device is investigated and mainly ascribed to the propagating plasmons, generated by the coupling of the 2DEG with incident MIR photons. Moreover, a linear detector array (LDA) of PbTe/Ge is demonstrated for a thermal imaging application, which exhibits promising high‐quality real‐time imaging via the 2D photodetector arrays on Ge‐based integrated circuits. This work opens up a new way for the development of next‐generation, advanced MIR photonic devices and integrated photonic systems. [ABSTRACT FROM AUTHOR]

While recent experiments confirm the existence of hundreds of topological electronic materials, only a few exhibit the coexistence of superconductivity (SC) and a topological electronic state. These compounds attract significant attention in forefront research because of the potential for the existence of topological SC, paving the way for future technological advancements. SrSn4 is known for exhibiting unusual SC below the transition temperature (TC) of 4.8 K. Recent theory predicts a topological electronic state in this compound, which is yet to be confirmed by experiments. Systematic and detailed studies of the magnetotransport properties of SrSn4 and its Fermi surface characterizations are also absent. For the first time, a quantum oscillation study reveals a nontrivial 흅‐Berry phase, very light effective mass, and high quantum mobility of charge carriers in SrSn4. Magnetotransport experiment unveils large linear transverse magnetoresistance (TMR) of more than 1200% at 5 K and 14 T. Angle‐dependent transport experiments detect anisotropic and fourfold symmetric TMR, with the maximum value (≈2000%) occurring when the angle between the magnetic field and the crystallographic b‐axis is 45°. The results suggest that SrSn4 is the first topological material with SC above the boiling point of helium that displays such high magnetoresistance. [ABSTRACT FROM AUTHOR]

Uniaxial stress has proven to be a powerful experimental tuning parameter for effectively controlling lattice, charge, orbital, and spin degrees of freedom in quantum materials. In addition, its ability to manipulate the symmetry of materials has garnered significant attention. Recent technical progress to combine uniaxial stress cells with quantum oscillation and angle-resolved photoemission techniques allowed to study the electronic structure as function of uniaxial stress. This review provides an overview on experimental advancements in methods and examines studies on diverse quantum materials, encompassing the semimetal WTe2, the unconventional superconductor Sr2RuO4, Fe-based superconductors, and topological materials. [ABSTRACT FROM AUTHOR]

The kagome metal CsV3Sb5 is an ideal platform to study the interplay between topology and electron correlation. To understand the fermiology of CsV3Sb5, intensive quantum oscillation (QO) studies at ambient pressure have been conducted. However, due to the Fermi surface reconstruction by the complicated charge density wave (CDW) order, the QO spectrum is exceedingly complex, hindering a complete understanding of the fermiology. Here, we directly map the Fermi surface of the pristine CsV3Sb5 by measuring Shubnikov-de Haas QOs up to 29 T under pressure, where theCDWorder is completely suppressed. The QO spectrum of the pristine CsV3Sb5 is significantly simpler than the one in the CDW phase, and the detected oscillation frequencies agree well with our density functional theory calculations. In particular, a frequency as large as 8,200 T is detected. Pressure-dependent QO studies further reveal a weak but noticeable enhancement of the quasiparticle effective masses on approaching the critical pressure where the CDW order disappears, hinting at the presence of quantum fluctuations. Our high-pressure QO results reveal the large, unreconstructed Fermi surface of CsV3Sb5, paving the way to understanding the parent state of this intriguing metal in which the electrons can be organized into different ordered states. [ABSTRACT FROM AUTHOR]

In this paper, we address the quantum estimation problem in the presence of quantum oscillations, which occur due to the use of the pulse technique when applied to two dissimilar superconducting qubits coupled by a fixed capacitor. This dissimilarity of the qubits is due to the arrangement of the Josephson junctions in the two qubits circuits. Investigating and detuning the performance improvement parameters of this system plays an important role in the design and construction of quantum circuits, especially Josephson parametric amplifiers (JPAs). To improve quantum metrology in this system, we use the quantum Fisher information (QFI) and the Hilbert-Schmidt speed (HSS) as tools for quantum estimation. The remarkable result is that the quantum estimation can be improved even in the presence of quantum oscillations. [ABSTRACT FROM AUTHOR]

Charge transport in solids at low temperature reveals a material's mesoscopic properties and structure. Under a magnetic field, Shubnikov-de Haas (SdH) oscillations inform complex quantum transport phenomena that are not limited by the ground state characteristics and have facilitated extensive explorations of quantum and topological interest in two- and three-dimensional materials. Here, in elemental metal Cr with two incommensurately superposed lattices of ions and a spin-density-wave ground state, we reveal that the phases of several low-frequency SdH oscillations in σxx (ρxx) and σyy (ρyy) are no longer identical but opposite. These relationships contrast with the SdH oscillations from normal cyclotron orbits that maintain identical phases between σxx (ρxx) and σyy (ρyy). We trace the origin of the low-frequency SdH oscillations to quantum interference effects arising from the incommensurate orbits of Cr's superposed reciprocal lattices and explain the observed π-phase shift by the reconnection of anisotropic joint open and closed orbits. [ABSTRACT FROM AUTHOR]

Kondo insulators have recently aroused great interest because they are promising materials that host a topological insulator state caused by the strong electron interactions. Moreover, recent observations of the quantum oscillations in the insulating state of Kondo insulators have come as a great surprise. Here, to investigate the surface electronic state of a prototype Kondo insulator YbB12, we measured the transport properties of single crystals and microstructures. In all samples, the temperature dependence of the electrical resistivity is insulating at high temperatures and the resistivity exhibits a plateau at low temperatures. The magnitude of the plateau value decreases with reducing sample thickness, which is quantitatively consistent with the surface electronic conduction in the bulk insulating YbB12. Moreover, the magnetoresistance of the microstructures exhibits a weak-antilocalization effect at low field. These results are consistent with the presence of a topologically protected surface state, suggesting that YbB12 is a candidate material for a topological Kondo insulator. The high field resistivity measurements up to µ0H = 50 T of the microstructures provide supporting evidence that the quantum oscillations of the resistivity in YbB12 occurs in the insulating bulk.

The Mott metal-insulator transition represents one of the most fundamental phenomena in condensed matter physics. Yet, basic tenets of the canonical Brinkman-Rice picture of Mott localization remain to be tested experimentally by quantum oscillation measurements that directly probe the quasiparticle Fermi surface and effective mass. By extending this technique to high pressure, we have examined the metallic state on the threshold of Mott localization in clean, undoped crystals of NiS3. We find that i) on approaching Mott localization, the quasiparticle mass is strongly enhanced, whereas the Fermi surface remains essentially unchanged; ii) the quasiparticle mass closely follows the divergent form predicted theoretically, establishing charge carrier slowdown as the driver for the metal-insulator transition; iii) this mass divergence is truncated by the metal-insulator transition, placing the Mott critical point inside the insulating section of the phase diagram. The inaccessibility of the Mott critical point in NiS2 parallels findings at the threshold of ferromagnetism in clean metallic systems, in which criticality at low temperature is almost universally interrupted by first-order transitions or novel emergent phases such as incommensurate magnetic order or unconventional superconductivity. [ABSTRACT FROM AUTHOR]

[Display omitted] We report an observation of quantum oscillations (QOs) in the correlated insulators with valley anisotropy of twisted double bilayer graphene (TDBG). The anomalous QOs are best captured in the magneto resistivity oscillations of the insulators at v = −2, with a period of 1/ B and an oscillation amplitude as high as 150 kΩ. The QOs can survive up to ∼10 K, and above 12 K, the insulating behaviors are dominant. The QOs of the insulator are strongly D dependent: the carrier density extracted from the 1/ B periodicity decreases almost linearly with D from −0.7 to −1.1 V/nm, suggesting a reduced Fermi surface; the effective mass from Lifshitz-Kosevich analysis depends nonlinearly on D , reaching a minimal value of 0.1 m e at D = ∼ −1.0 V/nm. Similar observations of QOs are also found at v = 2, as well as in other devices without graphite gate. We interpret the D sensitive QOs of the correlated insulators in the picture of band inversion. By reconstructing an inverted band model with the measured effective mass and Fermi surface, the density of state at the gap, calculated from thermal broadened Landau levels, agrees qualitatively with the observed QOs in the insulators. While more theoretical understandings are needed in the future to fully account for the anomalous QOs in this moiré system, our study suggests that TDBG is an excellent platform to discover exotic phases where correlation and topology are at play. [ABSTRACT FROM AUTHOR]

The connectivity and inherent frustration of the kagome lattice can produce interesting electronic structures and behaviors in compounds containing this structural motif. Here we report the properties of Pt 3 X 2 (X = In and Tl) that adopt a double-layer kagome net structure related to that of the topologically nontrivial high-temperature ferromagnet Fe3Sn2 and the density wave hosting compound V3Sb2. We examined the structural and physical properties of single crystal Pt3Tl2 and polycrystalline Pt3In2 using X-ray and neutron diffraction, magnetic susceptibility, heat capacity, and electrical transport measurements, along with density functional theory calculations of the electronic structure. Our calculations show that Fermi levels lie in pseudogaps in the densities of states with several bands contributing to transport, and this is consistent with our Hall effect, magnetic susceptibility, and heat capacity measurements. Although electronic dispersions, characteristic of simple kagome nets with nearest-neighbor hopping, are not clearly seen, likely due to the extended nature of the Pt 5 d states, we do observe moderately large and non-saturating magnetoresistance values and quantum oscillations in the magnetoresistance and magnetization associated with the kagome nets of Pt. [ABSTRACT FROM AUTHOR]

We develop a method to calculate the electron flow between an arbitrary atomic monolayer sheet and an arbitrary tube by expressing the corresponding sheet-tube tunneling matrix elements with those between sheets. We use this method to calculate the spin current from a monolayer silicene sheet with sublattice-staggered current-induced spin polarization to a silicene tube. The calculated sheet-to-tube spin current exhibits an oscillation as a function of the tube circumferential length because the Fermi points in the tube cross the Fermi circle in the sheet. Furthermore, the spin current with spin in the out-of-plane direction, which is absent in the sheet-sheet junction (including twisted sheets) with C 3 rotational symmetry, appears in an oscillating form in the tube-sheet junction due to the broken C 3 rotational symmetry. This is an example of the symmetry manipulation which realizes switching a particular component of the spin current. • The formula for electron flow between an atomic monolayer and a tube is developed. • Spin current from silicene sheet to tube is calculated using the formula. • Oscillations in the spin current occur due to the tube's momentum quantization. • Symmetry manipulation switches a particular component of the spin current. [ABSTRACT FROM AUTHOR]

We have detected a large Nernst effect in the charge density wave state of the multiband organic metal α-(BEDT-TTF)2KHg(SCN)4. We find that apart from the phonon drag effect, the energy relaxation processes that govern the electron–phonon interactions and the momentum relaxation processes that determine the mobility of the q1D charge carriers have a significant role in observing the large Nernst signal in the CDW state in this organic metal. The emphasised momentum relaxation dynamics in the low field CDW state ( CDW 0 ) is a clear indicator of the presence of a significant carrier mobility that might be the main source for observation of the largest Nernst signal. The momentum relaxation is absent with increasing angle and magnetic field, i.e., in the high-field CDW state ( CDW x ) as evident from the much smaller Nernst effect amplitude in this state. In this case, only the phonon drag effect and electron–phonon interactions are contributing to the transverse thermoelectric signal. Our findings advance and change previous observations on the complex properties of this organic metal. [ABSTRACT FROM AUTHOR]

1D TaSe3 exhibits many unusual physical properties due to its distorted type‐II chains. Ribbon‐shaped single crystals can be easily bended along the b‐axis, forming rings. This study investigates the magnetoresistance (MR) of TaSe3 up to 60 T in both unbended (ribbon shape) and ring‐shaped (bended ribbon) samples. Notable changes are found in the magnetotransport properties between the two different shaped samples. One is that the MR in ring‐shaped samples is three orders lower than that in unbended samples under the same sample environment. In addition, linear MR is observed above ≈20 T in ring‐shaped samples when the magnetic field is parallel or perpendicular to the rings. Quantum oscillations are also observed as a function of the magnetic field when the magnetic field is applied parallel to rings, possibly due to the Altshuler–Aronov–Spivak effect or the inversion of the lowest Landau level beyond the quantum limit. All these results are related to strain‐induced electronic structure change in TaSe3, an effective way to tune physical properties in low‐dimensional materials. [ABSTRACT FROM AUTHOR]

The transport properties, magnetoresistance, and Shubnikov–de Haas (ShH) oscillations of glass-coated Bi0.92Sb0.08 single-crystal wires with diameters of 180 nm to 2.2 μm and the (10 1) orientation along the wire axis, which are prepared by liquid phase casting, have been studied. For the first time, it has been found that the energy gap ΔE increases by a factor of four with a decrease in the wire diameter d owing to the manifestation of the quantum size effect. This significant increase in the energy gap can occur under conditions of an energy–momentum linear dispersion relation, which is characteristic of both the gapless state and the surface states of a topological insulator. It has been shown that, in a strong magnetic field at low temperatures, a semiconductor–semimetal transition occurs; it is evident in the temperature dependences of resistance in a magnetic field. An analysis of the ShH oscillations, namely, the phase shift of the Landau levels and the features of the angular dependences of the oscillation periods, suggests that the combination of the manifestation of the topological insulator properties and the quantum size effect leads to the occurrence of new effects in low-dimensional structures, which require new scientific approaches and applications in microelectronics. [ABSTRACT FROM AUTHOR]

High-temperature (HT) kagome magnets provide important platforms to explore nontrivial topological physics and promising potentials for spintronic applications, due to the complicated interactions among their electrons, lattices, and magnetism. Herein, the nontrivial electronic properties of a HT layered kagome-magnet, HoMn 6 Sn 6 , are systematically resolved by quantum oscillation measurements and density functional theory (DFT) calculations. The prominent Shubnikov-de Haas (SdH) oscillations under pulsed high magnetic fields reveal a high quantum mobility of 0.37 m 2 ·V -1 ·s -1 for this HT ferrimagnet. The observed multiple-frequency quantum oscillations exhibit various angular dependences, consistent with DFT calculations which suggest a complex Fermi topology of three three-dimensional hole pockets and two electron pockets. The observed π shift of the Berry phase for quantum oscillations unveils nontrivial topological properties in HoMn 6 Sn 6 , further confirmed by DFT calculated Dirac fermions and large anomalous Hall conductivity. Our findings establish HoMn 6 Sn 6 as an HT magnetic candidate for topological magnetoelectronics or spin quantum applications.

Quantum oscillation is an important phenomenon in low temperature transport studies of topological materials. In three-dimensional topological insulators, Dirac semimetals, Weyl semimetals, and other topological nontrivial materials, the topologically nontrivial band structure will add a phase correction to the quantum oscillation patterns, which is known as the nontrivial Berry phase. Berry phase analysis via quantum oscillation is a powerful method to investigate the nontrivial band topology of topological materials. In this review, we introduce the concepts of the Berry phase and quantum oscillations, and provide some classification of topological materials. We then employ some important studies on each type of topological material to discuss the nontrivial Berry phase. We conclude by pointing out the importance of quantum transport studies on topological materials, as well as drawing attention to the exploration of the nontrivial Berry phase in a new material system that could shed more light on the topology-based electronics.

Elemental Tellurium (Te) is an important p‐type semiconductor with wide practical applications. It is currently of great interest as a chiral crystal with broken inversion and mirror symmetries, and its topological nature is under active discussion. Here the Shubnikov–de Haas (SdH) oscillations with a nontrivial π Berry phase and the quantum linear magnetoresistance (MR) in as‐synthesized high‐mobility Te single crystals are reported. The vapor transport grown Te shows a hollow hexagonal prism structure with tunable carrier density and high mobility of about 1000 cm2 V−1 s−1 at low temperature. For concentration p > 1017 cm−3, the conspicuous SdH oscillations map out the dumbbell‐shaped Fermi surface and the long‐standing peculiar amplitude change with varying magnetic field orientation is explained by careful quantitative analyses. Pulsed magnetic field measurements up to 57 T disclose a quantum linear MR beyond the quantum limit and the Landau fan diagram clearly reveals a topologically nontrivial π Berry phase. This work paves way for the synthesis of high‐mobility Te structures and sheds light onto the intrinsic nontrivial topology of the attractive elemental substance. [ABSTRACT FROM AUTHOR]

The magnetotransport behavior inside the nematic phase of bulk FeSe reveals unusual multiband effects that cannot be reconciled with a simple two-band approximation proposed by surface-sensitive spectroscopic probes. In order to understand the role played by the multiband electronic structure and the degree of two-dimensionality, we have investigated the electronic properties of exfoliated flakes of FeSe by reducing their thickness. Based on magnetotransport and Hall resistivity measurements, we assess the mobility spectrum that suggests an unusual asymmetry between the mobilities of the electrons and holes, with the electron carriers becoming localized inside the nematic phase. Quantum oscillations in magnetic fields up to 38 T indicate the presence of a hole-like quasiparticle with a lighter effective mass and a quantum scattering time three times shorter, as compared with bulk FeSe. The observed localization of negative charge carriers by reducing dimensionality can be driven by orbitally dependent correlation effects, enhanced interband spin fluctuations, or a Lifshitz-like transition, which affect mainly the electron bands. The electronic localization leads to a fragile two-dimensional superconductivity in thin flakes of FeSe, in contrast to the two-dimensional high-Tc induced with electron doping via dosing or using a suitable interface. [ABSTRACT FROM AUTHOR]

The observation of 1/B-periodic behavior in Kondo insulators and semiconductor quantum wells challenges the conventional wisdom that quantum oscillations (QOs) necessarily arise from Fermi surfaces in metals. We revisit recently proposed theories for this phenomenon, focusing on a minimal model of an insulator with a hybridization gap between two opposite-parity light and heavy mass bands with an inverted band structure. We show that there are characteristic differences between the QO frequencies in the magnetization and the low-energy density of states (LE-DOS) of these insulators, in marked contrast to metals where all observables exhibit oscillations at the same frequency. The magnetization oscillations arising from occupied Landau levels occur at the same frequency that would exist in the unhybridized case. The LE-DOS oscillations in a disorder-free system are dominated by gap-edge states and exhibit a beat pattern between two distinct frequencies at low temperature. Disorder-induced in-gap states lead to an additional contribution to the DOS at the unhybridized frequency. The temperature dependence of the amplitude and phase of the magnetization and DOS oscillations are also qualitatively different and show marked deviations from the Lifshitz–Kosevich form well known in metals. We also compute transport to ensure that we are probing a regime with insulating upturns in the direct current (DC) resistivity. [ABSTRACT FROM AUTHOR]

In this work, we review single mode SiO₂ fiber Bragg grating techniques for dilatometry studies of small single-crystalline samples in the extreme environments of very high, continuous, and pulsed magnetic fields of up to 150 T and at cryogenic temperatures down to

We consider the semiclassical quantization condition for the energy of an electron in a magnetic field in the case when the electron orbit lies on a Fermi-surface pocket surrounding the Weyl point of a topological semimetal and analyze the constant γ appearing in this condition. It is shown that this constant has the universal value, γ = 0, independent on the tilt of the Weyl spectrum. Since the constant γ for an extremal cross section of the Fermi surface determines the phase of quantum oscillations, this result explains why measurements of the phase permit one to find Weyl points in crystals even though the extremal cross section of the pocket does not pass through this point, and the appropriate Berry phase of the orbit differs from π. [ABSTRACT FROM AUTHOR]

The noncentrosymmetric transition‐metal monopnictides NbP, TaP, NbAs, and TaAs are a family of Weyl semimetals in which pairs of protected linear crossings of spin‐resolved bands occur. These so‐called Weyl nodes are characterized by integer topological charges of opposite sign associated with singular points of Berry curvature in momentum space. In such a system, anomalous magnetoelectric responses are predicted, which should only occur if the crossing points are close to the Fermi level and enclosed by Fermi surface pockets penetrated by an integer flux of Berry curvature, dubbed Weyl pockets. TaAs is shown to possess Weyl pockets, whereas TaP and NbP have trivial pockets enclosing zero net flux of Berry curvature. Herein, via measurements of the magnetic torque, resistivity, and magnetization, a comprehensive quantum‐oscillation study of NbAs is presented, the last member of this family where the precise shape and nature of the Fermi surface pockets is still unknown. Seven distinct frequency branches, three of which have not been observed before, are detected. A comparison with density functional theory calculations suggests that the two largest pockets are topologically trivial, whereas the low frequencies might stem from tiny Weyl pockets. The enclosed Weyl nodes are within a few meV of the Fermi energy. [ABSTRACT FROM AUTHOR]

In this paper, we discuss coherent atomic oscillations between two weakly coupled Bose–Einstein condensates that are energetically different. The weak link is notionally provided by a laser barrier in a (possibly asymmetric) multi-well trap or by Raman coupling between condensates in different hyperfine levels. The resultant boson Josephson junction dynamics is described by a double-well nonlinear Gross–Pitaevskii equation. On the basis of a new set of Jacobian elliptic function solutions, we describe the period of the oscillations as well as associated quantities and predict novel observable consequences of the interplay of the energy difference and initial phase difference between the two condensate populations. [ABSTRACT FROM AUTHOR]

The connectivity and inherent frustration of the kagome lattice can produce interesting electronic structures and behaviors in compounds containing this structural motif. Here we report the properties of Pt3X2 (X = In and Tl) that adopt a double-layer kagome net structure related to that of the topologically nontrivial high-temperature ferromagnet Fe3Sn2 and the density wave hosting compound V3Sb2. We examined the structural and physical properties of single crystal Pt3Tl2 and polycrystalline Pt3In2 using X-ray and neutron diffraction, magnetic susceptibility, heat capacity, and electrical transport measurements, along with density functional theory calculations of the electronic structure. Our calculations show that Fermi levels lie in pseudogaps in the densities of states with several bands contributing to transport, and this is consistent with our Hall effect, magnetic susceptibility, and heat capacity measurements. Although electronic dispersions, characteristic of simple kagome nets with nearest-neighbor hopping, are not clearly seen, likely due to the extended nature of the Pt 5d states, we do observe moderately large and non-saturating magnetoresistance values and quantum oscillations in the magnetoresistance and magnetization associated with the kagome nets of Pt.

The quest for intrinsically ferromagnetic topological materials is a focal point in the study of topological phases of matter, as intrinsic ferromagnetism plays a vital role in realizing exotic properties such as the anomalous Hall effect (AHE) in quasi-two-dimensional materials, and this stands out as one of the most pressing concerns within the field. Here, we investigate a novel higher order member of the MnSb2nTe3n+1family, MnSb 12 Te 19 , for the first time combining magnetotransport and angle-resolved photoemission spectroscopy (ARPES) measurements. Our magnetic susceptibility experiments identify ferromagnetic transitions at temperature T c = 18.7 K, consistent with our heat capacity measurements ( T = 18.8 K). The AHE is observed for the field along the c -axis below T c . Our study of Shubinikov-de-Haas oscillations provides evidence for Dirac fermions with π Berry phase. Our comprehensive investigation reveals that MnSb 12 Te 19 exhibits a FM ground state along with AHE, and hole-dominated transport properties consistent with ARPES measurements., (© 2024 IOP Publishing Ltd. All rights, including for text and data mining, AI training, and similar technologies, are reserved.)

We have detected a large Nernst effect in the charge density wave state of the multiband organic metal α-(BEDT-TTF)2KHg(SCN)4. We find that apart from the phonon drag effect, the energy relaxation processes that govern the electron–phonon interactions and the momentum relaxation processes that determine the mobility of the q1D charge carriers have a significant role in observing the large Nernst signal in the CDW state in this organic metal. The emphasised momentum relaxation dynamics in the low field CDW state (CDW0) is a clear indicator of the presence of a significant carrier mobility that might be the main source for observation of the largest Nernst signal. The momentum relaxation is absent with increasing angle and magnetic field, i.e., in the high-field CDW state (CDWx) as evident from the much smaller Nernst effect amplitude in this state. In this case, only the phonon drag effect and electron–phonon interactions are contributing to the transverse thermoelectric signal. Our findings advance and change previous observations on the complex properties of this organic metal.

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The calculations and measurements of quantum corrections to the capacitances between the gates of a field-effect transistor and its channel located between these gates are performed. The cases when the channels are formed by one or two layers of two-dimensional electrons are studied. Qualitatively similar results are obtained for samples with a channel in wide and double quantum wells. Coincidence is established for the normalized values of the magnetocapacitances measured between different gates and the channel in the case when one electron layer in the channel is filled. Some specific features of the capacitance associated with the negative compressibility of electrons are revealed and explained in the case when two layers with different densities of electrons are filled. [ABSTRACT FROM AUTHOR]

The peculiar features in the manifestation of the properties of topological insulators (TIs) and quantum size effects on the longitudinal magnetoresistance (LM) (H ||I) of Bi–17 at % Sb single-crystal semiconductor wires prepared by liquid phase casting (Ulitovsky method) having orientation along the axis and diameters of 75–1000 nm have been studied. At high temperatures (T > 50 K), the quantum size effect is evident as an increase in the energy gap of ΔE ~ d–1 of the Bi-17 at % Sb semiconductor wires with a decrease in the wire diameter d. A decrease in temperature (T < 50 K) leads to a transition from the semiconductor dependence R(T) to the metallic dependence with a decrease in the wire diameter d; the transition indicates the presence of the surface states characteristic of TIs. In a diameter range of 200–350 nm, the Shubnikov de Haas (SdH) oscillations are observed on the longitudinal magnetoresistance H ||I in weak magnetic fields (H < 3 T); they are used to calculate the Dingle temperature, cyclotron masses, carrier mean free path, and charge carrier mobilities μ = 11 × 103 cm2/s. On the LM of the Bi–17 at % Sb wires at 4.2 K, a singularity in the form of phase shift of the Landau levels' index on the SdH oscillations and anomalous maximum in the thickness dependence of the LM at 4.2 K is observed; it is associated with the semiconductor-metal transition due to a significant contribution of the surface states of the TI to the conductivity. Taken together, the singularities on the LM, the phase shift of the SdH oscillations, high mobility and anisotropy of charge carriers, and an increase in conductivity with a decrease in the wire diameter d indicate the presence of surface states in thin semiconductor Bi1 – xSbx wires with a Fermi energy of the "Dirac cone" type, which are highly sensitive to the wire diameter, temperature, and the magnitude and direction of the magnetic field and lead to new peculiar features of the transport properties of topological insulators in the low-dimensional structures. [ABSTRACT FROM AUTHOR]