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The charge density wave (CDW) state is a widespread phenomenon in low-dimensional metals/semimetals. The spectral weight of the associated folded bands (shadow bands) can be an intriguing trigger leading to additional Fermi surface instability and unexplored phase transitions. The rare earth tri-telluride CeTe3 exhibits a single CDW stabilized below ~400 K and antiferromagnetism below ~3 K. The distinct periodicities between the Te-square net, the CeTe block layer, and the CDW give rise to rich shadow band formations. In this work, we reveal the predominant scattering between the original and shadow bands at 4 K, with the scattering within the original bands being relatively suppressed at Fermi energy. This unconventional quasi-particle scattering collectively underscores the vital role of the shadow bands' spectral weight and the hidden matrix element effect, which are crucial for controlling electronic properties in this system. Furthermore, our finding points to the existence of rich and unexplored Fermi surface instabilities, which potentially play a role in controlling the nature of long-range antiferromagnetism at lower temperatures in the presence of finite charge-spin interaction.

Let $A$ be an excellent two-dimensional normal local ring containing an algebraically closed field. Then $A$ is called an elliptic singularity if $p_f(A)=1$, where $p_f$ denotes the fundamental genus. On the other hand, the concept of almost Gorenstein rings was introduced by Barucci and Fr\"oberg for one-dimensional local rings and generalized by Goto, Takahashi and Taniguchi to higher dimension. In this paper, we describe almost Gorenstein rings in geometric language using resolution of singularities and give criterions to be almost Gorenstein. In particular, we show that elliptic singularities are almost Gorenstein. Also, for every integer $g\ge 2$, we provide examples of singularities that is almost Gorenstein (resp. not almost Gorenstein) with $p_f(A)=g$. We also provide several examples of determinantal singularities associated with $2\times 3$ matrices, which include both almost Gorenstein singularities and non-almost Gorenstein singularities., Comment: 25 pages

We report the synthesis and electronic properties of polycrystalline samples of Zr6MBi2 (M = Ru and Fe) crystallizing in the hexagonal Zr6CoAl2-type structure. Based on their electrical resistivity, magnetization, and heat capacity data, Zr6RuBi2 and Zr6FeBi2 are found to exhibit bulk superconductivity below Tc = 4.9 and 1.4 K, respectively. Although Zr6RuBi2 is most likely a conventional superconductor, the considerably higher Tc for M = Ru than that for M = Fe differs from the trend in Tc for Zr6CoAl2-type superconductors reported thus far. The superconductivity of an amorphous solid-solution phase, which may hinder elucidation of the superconducting properties of Zr6MBi2, is also discussed., Comment: 7 pages, 7 figures

Rare earth oxides have attracted interest as a platform for studying frustrated magnetism arising from bond dependent anisotropic interactions. Ordered rock salt compounds Na$_2$PrO$_3$ crystallize in two polymorphs ($\alpha$ and $\beta$) comprising honeycomb and hyperhoneycomb lattices of octahedrally coordinated Pr$^{4+}$ (4$f^1$). Although possible realization of antiferromagnetic Kitaev interactions is anticipated for these phases on the basis of ab initio models, the air-sensitivity of the two polymorphs has hampered reliable crystal growth and physical property measurements. Here, we have succeeded in preparing powder and single crystals of both $\alpha$- and $\beta$-Na$_2$PrO$_3$ using modified synthetic procedures. Revised crystal structures for both polymorphs are obtained from refinement of untwinned single-crystal X-ray diffraction data., Comment: 13 pages, 8 figures

The physics of spin-orbit entangled magnetic moments of $4d$ and $5d$ transition metal ions on a honeycomb lattice has been much explored in search for unconventional magnetic orders or quantum spin liquids expected for compass spin models, where different bonds in the lattice favour different orientations for the magnetic moments. Realizing such physics with rare-earth ions is a promising route to achieve exotic ground states in the extreme spin orbit limit, however this regime has remained experimentally largely unexplored due to major challenges in materials synthesis. Here we report successful synthesis of powders and single crystals of $\beta$-Na$_2$PrO$_3$, with $4f^{1}$ Pr$^{4+}$ $j_\mathrm{eff}\!=\!1/2$ magnetic moments arranged on a hyperhoneycomb lattice with the same threefold coordination as the planar honeycomb. We find a strongly noncollinear magnetic order with highly dispersive gapped excitations that we argue arise from frustration between bond-dependent, anisotropic off-diagonal exchanges, a compass quantum spin model not explored experimentally so far. Our results show that rare-earth ions on threefold coordinated lattices offer a platform for the exploration of quantum compass spin models in the extreme spin orbit regime, with qualitatively distinct physics from that of $4d$ and $5d$ Kitaev materials., Comment: 22 pages in total, main text (9 pages) + supplementary information

GRAMS (Gamma-Ray and AntiMatter Survey) is a next-generation balloon/satellite experiment utilizing a LArTPC (Liquid Argon Time Projection Chamber), to simultaneously target astrophysical observations of cosmic MeV gamma-rays and conduct an indirect dark matter search using antimatter. While LArTPCs are widely used in particle physics experiments, they have never been operated at balloon altitudes. An engineering balloon flight with a small-scale LArTPC (eGRAMS) was conducted on July 27th, 2023, to establish a system for safely operating a LArTPC at balloon altitudes and to obtain cosmic-ray data from the LArTPC. The flight was launched from the Japan Aerospace Exploration Agency's (JAXA) Taiki Aerospace Research Field in Hokkaido, Japan. The total flight duration was 3 hours and 12 minutes, including a level flight of 44 minutes at a maximum altitude of 28.9~km. The flight system was landed on the sea and successfully recovered. The LArTPC was successfully operated throughout the flight, and about 0.5 million events of the cosmic-ray data including muons, protons, and Compton scattering gamma-ray candidates, were collected. This pioneering flight demonstrates the feasibility of operating a LArTPC in high-altitude environments, paving the way for future GRAMS missions and advancing our capabilities in MeV gamma-ray astronomy and dark matter research.

We prove that two formulas of the orbital magnetic susceptibility, namely, Koshino-Ando's formula and G\'{o}mez-Santos and Stauber's formula, are equivalent for the tight-binding models. The difference between these two formulas can be written in a form containing the surface terms arising from the momentum-space integration, and we show that the surface terms are exactly vanishing although the primitive functions are seemingly non-periodic with respect to the translation by the reciprocal lattice vector., Comment: 2 pages

Analogous to the charged electron-electron pair condensation in superconductors, an excitonic insulator (EI) represents Fermi surface instability due to spontaneous formation and condensation of charge-neutral electron-hole pair (exciton). Unlike in superconductors, however, the charge-neutral nature of exciton makes probing emergent EI phase via macroscopic physical properties generally difficult. Here, we propose a van der Waals coupled antiferromagnetic semiconductor GdGaI (GGI) as a new material category leading to emergent multi-q magnet intertwined with spontaneous exciton formation/condensation. Before excitonic band hybridization, a simple picture for the parent electronic state consists of electron (Gd-derived 5d) and hole (Ga-derived 4p) delocalized bands, together with Gd-derived 4f localized antiferromagnets with S = 7/2 classical nature. Through intra Gd atom 4f-5d Hund's coupling, a notable finding is the emergent minimum length scale (2a) Skyrmion-like spin texture resulting from spontaneous condensation/formation of spin-polarized exciton with BCS-BEC crossover phenomenology. This discovered platform is promising for realizing valuable quantum matter on the nanoscale; our finding will provide significant insight into designing the atomic scale topological magnetism out of itinerant systems., Comment: 23 pages, 10 figures

In the field of fractional Chern insulators, a great deal of effort has been devoted to characterizing Chern bands that exhibit properties similar to the Landau levels. Among them, the concept of the vortex function, which generalizes the complex coordinate used for the symmetric-gauge Landau-level basis, allows for a concise description. In this paper, we develop a theory of constructing the vortex function and basis states of Chern insulators in the tight-binding formalism. In the first half, we consider the optimization process of the vortex function, which minimizes an indicator that measures the difference from the ideal Chern insulators. In particular, we focus on the sublattice position dependence of the vortex function or the quantum geometric tensor. This degree of freedom serves as a discrete analog of the non-uniformity in the spatial metric and magnetic field in a continuous model. In the second half, we construct two types of basis sets for a given vortex function: radially localized basis set and coherent-like basis set. The former basis set is defined as the eigenstates of an analogy of the angular momentum operator. Remarkably, one can always find exact zero mode(s) for this operator, which is explained by the celebrated Atiyah-Singer index theorem. As a byproduct, we propose an inequality rooted in the band topology. We also discuss the subtle differences between our formalism and the previous works about the momentum-space Landau level. The latter basis set generalizes the concept of coherent states on von Neumann lattice. While this basis set is not orthogonal, it is useful to compare the LLL and the given Chern insulator directly in the Brillouin zone. These basis sets are expected to be useful for many-body calculations of fractional Chern insulators., Comment: 14 pages, 4 figures, several discussions are added

Let $(A, \mathfrak{m})$ be a Gorenstein local ring, and $\mathcal{F} =\{F_n \}_{n\in \mathbb{Z}}$ a Hilbert filtration. In this paper, we give a criterion for Gorensteinness of the associated graded ring of $\mathcal{F}$ in terms of the Hilbert coefficients of $\mathcal{F}$ in some cases. As a consequence we recover and extend a result proved by Okuma, Watanabe and Yoshida. Further, we present ring-theoretic properties of the normal tangent cone of the maximal ideal of $A=S/(f)$ where $S=K[\![x_0,x_1,\ldots, x_m]\!]$ is a formal power series ring over an algebraically closed field $K$, and $f=x_0^a-g(x_1,\ldots,x_m)$, where $g$ is a polynomial with $g \in (x_1,\ldots,x_m)^b \setminus (x_1,\ldots,x_m)^{b+1}$, and $a, \, b, \, m$ are integers. We show that the normal tangent cone $\overline{G}(\mathfrak{m})$ is Cohen-Macaulay if $A$ is normal and $a \le b$. Moreover, we give a criterion of the Gorensteinness of $\overline{G}(\mathfrak{m})$., Comment: Comments are welcome

The back-linked Fabry-Perot interferometer (BLFPI) is an interferometer topology proposed for space gravitational wave antennas with the use of inter-satellite Fabry-Perot interferometers. The BLFPI offers simultaneous and independent control over all interferometer length degrees of freedom by controlling the laser frequencies. Therefore, BLFPI does not require an active control system for the physical lengths of the inter-satellite Fabry-Perot interferometers. To achieve a high sensitivity, the implementation must rely on an offline signal process for subtracting laser frequency noises. However, the subtraction has not been experimentally verified to date. This paper reports a demonstration of the frequency noise subtraction in the frequency band of 100 Hz-50 kHz, including the cavity pole frequency, using Fabry-Perot cavities with a length of 46 cm. The highest reduction ratio of approximately 200 was achieved. This marks the first experimental verification of the critical function in the BLFPI., Comment: 13 pages, 8 figures

The torsion pendulum is a prevailing instrument for measuring small forces acting on a solid body or those between solid bodies. While it offers powerful advantages, the measurement precision suffers from thermal noises of the suspending wires giving rise to stochastic torque noises. This letter proposes a new scheme to reduce the effect of such noise by employing a double torsion pendulum and cross-correlation technique based on the theoretical analysis that the thermal torque noise appears at each end of the suspending wire differentially. Cross-correlating two synthesized data streams which are composed of the rotation angles of two torsion stages, it yields the power spectral density estimate of external forces acting on the lower stage with the reduced effect from the thermal torque noises. As an example use case, we discuss the application to the study on the coupling strength of ultra light dark matter to standard model particles. Our evaluation indicates that the upper limit may be improved by an order of magnitude than the previous experiments at 2 mHz, which corresponds to about $8\times10^{-18}$ eV., Comment: 6 pages, 3 figures

Human and/or asset tracking using an attached sensor units helps understand their activities. Most common indoor localization methods for human tracking technologies require expensive infrastructures, deployment and maintenance. To overcome this problem, environmental sounds have been used for infrastructure-free localization. While they achieve room-level classification, they suffer from two problems: low signal-to-noise-ratio (SNR) condition and non-uniqueness of sound over the coverage area. A microphone localization method was proposed using supervised spectral decomposition and spatial likelihood to solve these problems. The proposed method was evaluated with actual recordings in an experimental room with a size of 12 x 30 m. The results showed that the proposed method with supervised NMF was robust under low-SNR condition compared to a simple feature (mel frequency cepstrum coefficient: MFCC). Additionally, the proposed method could be easily integrated with prior distribution, which is available from other Bayesian localizations. The proposed method can be used to evaluate the spatial likelihood from environmental sounds., Comment: 6 pages, 6 figures, accepted to IEEE/SICE SII 2023

Let $V$ be an affine algebraic variety, and let $p\in V$ be a singular point. For a regular function $g$ on $V$ such that $g(p)=0$ and for a positive integer $n$, we consider the cyclic covering $\phi_n\: V_n \to V$ of degree $n$ branched along the hypersurface defined by $g$. We will prove that for sufficiently large $n$, the tangent cone of $V_n$ at $\phi_n^{-1}(p)$ is, as an affine variety, the product of the tangent cone of the branch locus and the affine line. In particular, the multiplicity of the singularity $\phi_n^{-1}(p) \in V_n$, which is a function of $n$ determined by $V$ and $g$, remains constant for sufficiently large $n$. This result generalizes Tomaru's theorem for normal surface singularities., Comment: 8 pages; To appear in Tsukuba J. Math

Epitaxial thin films of SrTaO$_3$ with thickness ($t$) smaller than 74 nm were successfully fabricated on an insulator (LaAlO$_3$)$_{0.3}$(Sr$_2$AlTaO$_6$)$_{0.7}$ substrate. Films with $t$ above 8.6 nm showed metallic conduction. Both conductivity and a mobility showed a decrease with increasing $t$ above 42 nm, suggesting the instability of thick SrTaO$_3$ films. This instability was also supported by TEM image and XRD intensity. For the metallic films with $t$ below 25 nm, energy band splitting due to spin-orbit coupling ($\Delta$$_{so}$) and Rashba parameter ($\alpha$$_R$) were deduced from an analysis of a magnetoresistance using two-dimensional weak antilocalization theory. The values of $\Delta$$_{so}$ ranged from 26 to 120 meV, which were the largest among other metallic oxide films, such as SrNbO$_3$, SrIrO$_3$, and La$_{2/3}$Sr$_{1/3}$MnO$_3$ thin films, indicating that spin-orbit coupling in SrTaO$_3$ was the largest among the metallic perovskite oxides reported so far. The values of $\alpha$$_R$ for our SrTaO$_3$ films ranged from $8.8 \times$10$^{-13}$ to $1.7 \times$10$^{-12}$ eV m, which were much larger than those reported for other metallic oxide thin films., Comment: 17 pages, 8 figures

We report the synthesis, electronic properties, and electronic states of Zr6MTe2 (M = Cr, Mn, Fe, and Co), which is isostructural to a recently discovered superconductor family Sc6MTe2. Based on the electrical resistivity and heat capacity data measured at low temperatures, Zr6FeTe2 is found to show bulk superconductivity below Tc = 0.76 K. Zr6CoTe2 also exhibited zero resistivity due to superconductivity below 0.13 K. In contrast, Zr6+dMn1-dTe2 does not show superconductivity but instead exhibits strong magnetism, which most likely prevents the formation of superconductivity in this material. The electronic properties and electronic states of Zr6MTe2 are discussed in comparison with those of Sc6MTe2., Comment: 5 pages, 5 figures, accepted for publication in J. Phys. Soc. Jpn

We have reached a practical and realistic phase in human-support dialogue agents by developing a large language model (LLM). However, when requiring expert knowledge or anticipating the utterance content using the massive size of the dialogue database, we still need help with the utterance content's effectiveness and the efficiency of its output speed, even if using LLM. Therefore, we propose a framework that uses LLM asynchronously in the part of the system that returns an appropriate response and in the part that understands the user's intention and searches the database. In particular, noting that it takes time for the robot to speak, threading related to database searches is performed while the robot is speaking., Comment: This paper is part of the proceedings of the Dialogue Robot Competition 2023

A general free bosonic system with a pairing term is described by a bosonic Bogoliubov-de Gennes (BdG) Hamiltonian. The representation is given by a pseudo-Hermitian matrix, which is crucially different from the Hermitian representation of a fermionic BdG Hamiltonian. In fermionic BdG systems, a topological invariant of the whole particle (hole) bands can be nontrivial, which characterizes the Andreev bound states (ABS) including Majorana fermions. In bosonic cases, on the other hand, the corresponding topological invariant is thought to be trivial owing to the stability condition of the bosonic ground state. In this Letter, we consider a two-dimensional model that realizes a bosonic analogy of the ABS. The boundary states of this model are located outside the bulk bands and are characterized by a nontrivial Berry phase (or polarization) of the hole band. Furthermore, we investigate the zero-energy flat-band limit in which the Bloch Hamiltonian is defective, where the particle and hole states are identical to each other. In this limit, the Berry phase is $\mathbb{Z}_2$ quantized thanks to an emergent parity-time symmetry. This is an example of a topological invariant that uses the defective nature as a projection structure. Thus, boundary states in our model are essentially different from Hermitian topological modes and their variants., Comment: 5+1 pages, 1+1 figures

Whereas point-gap topological phases are responsible for exceptional phenomena intrinsic to non-Hermitian systems, their realization in quantum materials is still elusive. Here we propose a simple and universal platform of point-gap topological phases constructed from Hermitian topological insulators and superconductors. We show that (d-1)-dimensional point-gap topological phases are realized by making a boundary in d-dimensional topological insulators and superconductors dissipative. A crucial observation of the proposal is that adding a decay constant to boundary modes in d-dimensional topological insulators and superconductors is topologically equivalent to attaching a (d-1)-dimensional point-gap topological phase to the boundary. We furthermore establish the proposal from the extended version of the Nielsen-Ninomiya theorem, relating dissipative gapless modes to point-gap topological numbers. From the bulk-boundary correspondence of the point-gap topological phases, the resultant point-gap topological phases exhibit exceptional boundary states or in-gap higher-order non-Hermitian skin effects., Comment: 6+6 pages, 4+4 figures, 1+0 table

The non-Hermitian skin effects are representative phenomena intrinsic to non-Hermitian systems: the energy spectra and eigenstates under the open boundary condition (OBC) drastically differ from those under the periodic boundary condition (PBC). Whereas a non-trivial topology under the PBC characterizes the non-Hermitian skin effects, their proper measure under the OBC has not been clarified yet. This paper reveals that topological enhancement of non-normality under the OBC accurately quantifies the non-Hermitian skin effects. Correspondingly to spectrum and state changes of the skin effects, we introduce two scalar measures of non-normality and argue that the non-Hermitian skin effects enhance both macroscopically under the OBC. We also show that the enhanced non-normality correctly describes phase transitions causing the non-Hermitian skin effects and reveals the absence of non-Hermitian skin effects protected by average symmetry. The topological enhancement of non-normality governs the perturbation sensitivity of the OBC spectra and the anomalous time-evolution dynamics through the Bauer-Fike theorem., Comment: 36 pages, 15 figures

Let $A$ be a two-dimensional excellent normal Gorenstein local domain. In this paper, we characterize elliptic ideals $I \subset A$ for its normal tangent cone $\overline{G}(I)$ to be Gorenstein. Moreover, we classify all those ideals in a Gorenstein elliptic singularity in the characteristic zero case., Comment: 20 pages. To appear in Journal of Pure and Applied Algebra