The Particle Data Group lists only a few ground states and orbitally excited states for B-mesons, with very little experimental data for higher excited states. Various theoretical studies have been conducted on the B-meson family for 1S and 1P states. But, the theoretical models disagree on the placement of the newly observed B_{J}(5840)^{0,+}
and B_{J}(5960)^{0,+} ,and the strange bottom mesons, B_{sJ}(6064) and B_{sJ}(6114). Thus, there is a need to re-examine the higher excited states from a theoretical perspective.

In this study, we examine the properties of the 1F state using heavy quark effective theory (HQET), an effective theory describing the dynamics of heavy-light hadrons. HQET implements two approximate symmetries: the heavy quark symmetry and the chiral symmetry of light quarks. Using the HQET Lagrangians, we estimate the two body strong decays of heavy-light mesons and the coupling coefficients.

Further, using the experimental data from different experimental facilities, the 1F B-meson states are analyzed. This is done on the basis of two aspects, the masses of non-strange and strange 1F bottom meson states, and the decay behavior and channels of these states.

We first calculate the masses using averaged masses for charm mesons and heavy quark symmetry parameters. Thereafter, we estimate the masses of non-strange and strange 2^{+}(1^{3}F_{2}), 3^{+}(1F_{3}), 3^{+}(1F’_{3}), and 4^{+}(1^{3}F_{4}). The calculated masses are in good agreement with the existing theoretical models.

We next use the masses to compute the decay widths using pseudoscalar particles in the form of coupling constants. By comparing the calculated strong decay widths with the theoretical total decay widths, we find the upper bounds for associated couplings. While the lack of experimental data does not allow the calculation of the coupling constants from heavy quark symmetry, we are able to estimate the upper bounds for them. Finally, we construct Regge trajectories in the (J, M^{2}) plane and our predictions fit nicely on Regge lines.

Overall, our findings can provide new directions to high energy experiments that are on the lookout for new particles and open doors to a deeper understanding of the fundamental structure of matter.

]]>One of the central problems in nuclear physics concerns the origin of the short-range repulsive nuclear force. It is suggested that this repulsive force can be explained based on the spin-spin interaction between quarks and the Pauli-forbidden states at the quark level. In particular, it is necessary to explore what is known as the “10-plet quark–Pauli forbidden state” in the flavor SU(3) symmetry.

The Σ^{+}*p *scattering channel is considered one of the best channels for studying the 10-plet state. Specifically, the strength of the repulsive interaction is related to the differential cross-section for this scattering. However, theoretical predictions of the differential scattering cross-section in the momentum region above 400 MeV/c gives varying results. It is, therefore, necessary to determine this scattering cross-section experimentally.

Recently, an international team of researchers conducted a high-statistics Σ^{+}*p *scattering experiment at the Japan Proton Accelerator Research Complex (J-PARC) Hadron Experimental Facility. First, Σ^{+} particles were generated in a liquid hydrogen (or LH_{2}) target. The Σ^{+}*p* scattering events were then produced by colliding the Σ^{+} particles with the LH_{2 }target. To identify these events, the team used the magnetic spectrometer systems to reconstruct the incident momentum of Σ^{+} particles and the CATCH detector system to detect the recoil protons of the scattering events.

The team identified around 2400 events, 80 times more than that recorded in past experiments, in the momentum range of (0.44 – 0.8) GeV/c, and estimated the differential scattering cross-section for three separate momentum regions. Compared to past experiments, their results had lower uncertainties and significantly better quality. The calculated differential cross section was smaller than those predicted by theoretical models.

Further, the team estimated the phase shift of the * ^{3}S_{1}*
channel, which is related to the quark Pauli effect, for the first time. This provided a strong constraint on the strength of the repulsive force.

Overall, this study will provide a deeper understanding of the repulsive nuclear force, and, hopefully, further our understanding of matter and the Universe as a whole.

Heavy fermion UTe_{2} is one of the hottest topics in condensed matter physics. This is because of its unconventional superconducting properties, such as high field-reentrant superconductivity and multiple superconducting phases under pressure. Superconductivity is achieved owing to the formation of superconducting Cooper pairs of electrons. In UTe_{2}, the unconventional pairing mechanism must be responsible for this; thus, the spin-triplet state is expected. It is crucial to investigate the electronic state microscopically, that is, to determine the Fermi surfaces using a microscopic experimental probe combined with a band theory.

A powerful experimental probe is the quantum oscillation measurement method, such as the de Haas–van Alphen (dHvA) effect, which is the oscillatory effect in magnetization caused by the quantization of cyclotron motions in high magnetic fields. Three conditions must be satisfied to detect quantum oscillations: low temperature, high magnetic field, and high-quality single crystals. These are somewhat difficult experimental conditions. In particular, high-quality single crystals are inevitably crucial for UTe_{2} with strong electronic correlations.

In this study, we grew the ultrapure single crystals of UTe_{2} using “a new recipe” of a single crystal growth technique, as demonstrated by a high and sharp superconducting transition in specific heat measurements. Using this high-quality single crystal, we successfully detected quantum oscillations (the dHvA effect) for the first time in UTe_{2}. By rotating the field directions, the topology of Fermi surfaces is precisely determined experimentally. The results are consistent with the band structure calculations, indicating the existence of two types of cylindrical Fermi surfaces from the hole and electron bands. The dHvA signals are detected only at extremely low temperatures below 0.12 K, revealing the heavy effective mass resulting from strong electronic correlations.

The bare band structure calculations based on the 5f-itinerant model predict a small bandgap at the Fermi energy level, indicating a Kondo insulator. This is inconsistent with the real system because UTe_{2}
is a good metal with a large carrier number. To explain the experimental results obtained from the band calculations, we need to introduce the onsite Coulomb interaction, *U*. This suggests a possible mixed valence state of UTe_{2}.

As Fermi surfaces, known as the “face of metal,” are essential information for the electronic states, our results are a good starting point for clarifying unusual phenomena in UTe_{2} and other unconventional superconductors.

(Written by D. Aoki on behalf of all the authors.)

Electrical resistivity of a crystal is the measure of how easily electrons flow in it under the influence of an external electrical field. Although it is a familiar physical quantity, important insights can still be gathered by investigating it. Resistivity originates from collisions of electrons with other scatters, such as electrons and phonons. Its temperature dependence is indicative of the most common scattering event in the given temperature range. For example, according to Landau’s Fermi liquid theory, the scattering between two electrons produces resistivity, which depends quadratically on temperature. This is a consequence of the fact that electrons are fermions, and it also demonstrates that electrons carrying a current can be treated as “quasiparticles”.

However, a variety of strongly correlated metals exhibit a puzzling linear dependence of resistivity on temperature, referred to as *“strange metal”* behavior, inside the temperature regime in which electron-electron scattering is dominant. This challenges the “quasiparticle” explanation of charge transport. So far, in many cases, such *T*-linear resistivity has been observed when an antiferromagnetic transition is suppressed to zero temperature. This indicates that the intensification of spin fluctuations might be the source of the observed *strange metal* behavior. Indeed, several theories have been developed that corroborate this hypothesis.

This study presents systematic measurements of the electrical resistivity of single crystals of the iron-based superconductor, Ba_{1-x}Rb* _{x}*Fe

Recently, several quantum materials have been observed to exhibit an intrinsic instability of electrons towards the spontaneous rotational breaking of the underlying lattice. Based on an analogy with nematic liquid crystals, this state is called the electronic nematic state. Our conclusions suggest that fluctuations of an electronic nematic order can lead to

(Written by Kousuke Ishida on behalf of all authors)

In 1957, Kubo established the linear response theory to kinetic perturbation (e.g., electric or magnetic field). In the following years, based on the combination of the thermal Green's function technique with the Kubo formula, the linear response theory has emerged as a powerful practical tool for analyzing quantum transport and the magnetic response of materials. In contrast, the linear response theory to thermodynamic perturbation (e.g., temperature gradient) was advocated by Luttinger in 1964. Luttinger succeeded in treating the temperature gradient as a kinetic perturbation by introducing a fictitious gravitational field (scalar field). Since 2018, the authors and their co-workers have been developing the Luttinger formula together with the thermal Green's function technique to determine the thermal response (i.e., thermoelectric (TE) effect and thermal transport) of materials from a quantum mechanical perspective. The developed technique has been successfully applied to various materials exhibiting interesting TE effects that cannot be explained in terms of the Boltzmann transport theory (BTT).

In this study, as a typical thermal response beyond the BTT framework, the authors investigated the TE response in Mott variable-range hopping (VRH) using the above-mentioned Kubo–Luttinger (KL) theory together with the thermal Green's function technique. By incorporating the energy dependence of the localization length near the mobility edge based on the scaling theory of Anderson localization, we clarified that the Seebeck coefficient *S*(T) varies according to *S* ∝ *T ^{d}*

This study enables precise prediction of the performance of disordered TE materials exhibiting Mott VRH. The development of such a complete quantum theory that precisely predicts TE properties will play a role in realizing a sustainable society.

(Written by T. Yamamoto on behalf of all the authors.)

Researchers have previously constructed a solution representing the tachyon vacuum (a state with no D-branes at all). This solution requires an operator set (K,B,c) that satisfies a *KBc *algebra.

In this study, we present a general method for obtaining various solutions in SFT based on a solution that can be constructed with (K,B,c). To check this formalism, we have shown that this method reproduces known solutions that have been constructed previously by other methods.

Our methodology relies on the fact that a solution consisting of (K,B,c) remains a solution for another set (K',B',c') that satisfies the same *KBc* algebra as the original set. Notably, the new (K',B',c') set may consist of matter operators as well as the original (K,B,c) set.

In order to construct a new (K',B',c') set like this, we first constructed two operations in the original (K,B,c) space. These corresponded to the interior product and the Lie derivative. We defined these operations to satisfy the *KBc* algebra as proper operations in the (K,B,c) space. We then obtained the new (K',B',c') set through successive application of the Lie derivatives that were specified by a one-parameter family of “tangent vectors.”

Next, we applied our method to generate two known solutions representing a single D-brane with matter operators by starting from a single D-brane solution without matter operators. Thus, we identified a new (K',B',c') set and the one-parameter family of tangent vectors associated with each of the two D-brane solutions with matter operators.

While we have primarily reproduced simpler solutions that are already known, we believe that our formalism is capable of generating unknown solutions in SFT that are physically interesting. Moreover, the fact that the operations in the space of (K,B,c) are the same as those in the theory of differential forms could provide a deeper understanding of the mathematical structure of SFT along with a unified description of classical D-brane solutions.

]]>Ferroelectric materials are widely used as capacitors that can store a large electric charge as well as non-volatile memory (FeRAM), piezoelectric devices, and actuators. In strontium titanate (SrTiO_{3}), ferroelectricity is suppressed by quantum fluctuations, resulting in quantum paraelectricity below the structural phase transition temperature (*T*_{c} = 105 K). Furthermore, it has been demonstrated that applying an external force weakens quantum fluctuation, resulting in the appearance of the ferroelectric state. There are two methods for applying an external force (pressure) to crystals. In the case of hydrostatic pressure, the external force causes isotropic compression in the crystals and almost uniform lattice distortion. However, in the case of uniaxial pressure, anisotropic lattice distortion that cannot be achieved by hydrostatic pressure is easily generated when an external force is applied in a specific direction. By applying uniaxial pressure, an internal force is generated in the crystals based on the laws of action and reaction. This internal force is generally called “(uniaxial) stress”. When the external force is large, lattice distortion is concentrated around the defects owing to the increase in dislocations. To quantitatively evaluate such non-uniform lattice distortions, a new experimental technique is expected to be developed.

Birefringence is well known to be responsible for the phenomenon of double refraction, which occurs when a ray of light passes through calcite. The difference in refractive indices causes retardation, which provides information about lattice distortion, dielectric properties, and magnetism. Therefore, birefringence measurements have been widely used for many years. However, evaluating the non-uniform state has been difficult because conventional measurements using a laser beam can observe it at only one point. To solve this issue, the authors were able to obtain two-dimensional birefringence images under an external force.

In this study, when an external force was applied along [001] in quantum paraelectric SrTiO_{3}, the ferroelectric state induced by normal stress appeared almost uniformly below 20 K. However, when an external force was applied along [1-10], a large lattice distortion that was impossible to attain was generated, and complex-shaped domains emerged below *T*_{c} owing to the simultaneous generation of the normal and shear stresses. Although the temperature dependence of retardance in each domain was investigated, the ferroelectric state could not be observed. This could be because, under our experimental conditions, the degree of lattice distortion never reached a critical value without breaking the crystal. If the birefringence can be efficiently mined from large amounts of image data by using statistics and AI, there is a possibility that new physical phenomena will be discovered under non-uniform lattice distortion.

(Written by H. Manaka on behalf of all authors).

]]>Recently, the actinide compound UTe_{2} has been intensively studied as a novel candidate material for a spin-triplet superconductor, which is expected to host Majorana particles utilized for quantum computation. The superconductivity of this material without a magnetic order renders it ideal for research on pure spin-triplet superconductors. The possibility of a non-unitary pairing state in UTe_{2} is also discussed, indicating that UTe_{2} is a Weyl superconductor that has topologically protected point nodes with monopole charges in the superconducting gap. However, the symmetry and gap structures, which determine its topological properties, remain controversial. Therefore, an effective method for probing the order parameter of UTe_{2} is lacking.

In this study, the intrinsic anomalous thermal Hall effect, which is a fundamental property of Weyl superconductors, is investigated. The pairing state in the spin-triplet superconductor is characterized by a three-dimensional odd-parity order parameter, referred to as a *d*-vector. The basis of the *d*-vector corresponds to the irreducible representations (IRs) of the D_{2h} point group. When symmetry is reduced by the application of an external field, the admixture of these IRs is formed, which results in non-unitary pairing. We calculate the thermal Hall conductivity for the possible non-unitary pairing states in UTe_{2} as a function of the ratio “*r*” of the amplitudes of two mixed IRs. The intrinsic anomalous thermal Hall conductivity can be obtained by the integration of the Chern number, which corresponds to an integration of the Berry curvature over the Brillouin zone. Since the Berry curvature arises from the Weyl point nodes with monopole charges, the intrinsic thermal Hall conductivity directly reflects the distribution of the point nodes on the Fermi surfaces.

The relationship between the Hall conductivity and the point node structure is evident in the case of a simple ellipsoid-shaped Fermi surface, which is the minimum model that reflects the orthorhombic crystal structure. The admixture of IRs causes a splitting of the point nodes, because of which they move away from the high-symmetry axis. When one point node splits into two, the split nodes become Weyl points that have monopole charges with opposite signs. In this case, a Berry curvature exists along a certain direction, with a finite Chern number. This results in a finite thermal Hall conductivity, the magnitude of which depends on the distance between the point nodes.

The change in the point node structure due to the admixture of the two IRs is unique for each *d*-vector and is useful for the distinction of the order parameters based on future thermal conductivity measurements.

(Written by Y. Moriya on behalf of all the authors.)

]]>Particles suspended in laminar flows through uniform, straight tubes are expected to move parallel to the tube axis. However, in experiments, particles migrate across streamlines due to the lifts induced by inertia, particle deformability, medium elasticity and so on. As a result, they pass through specific locations in the downstream cross-section. The presence of inertial lift was first reported concerning circular tube flows, where spherical particles suspended in a Newtonian fluid migrated towards an annulus located at approximately 0.6 times the tube radius from the tube centerline, named “inertial focusing”. In rectangular tube flows typically adopted in microfluidics, particles migrate towards several discrete points in the downstream cross-section. Particularly concerning square tube flows, spherical particles suspended in Newtonian fluids become concentrated at four points near the center of the side walls.

Recently, inertial focusing phenomena have gained considerable attention in the field of microfluidics owing to their promising application in separating and filtering biological cells. This flow-based separating technique using microfluidic devices is based on differences in the inertial focusing behavior of cells, depending on their size and deformability. Although biological cells are somewhat deformable, and suspending media usually contain various polymers, it is unclear how cell deformability and medium elasticity affect inertial focusing.

This study experimentally investigated the inertial focusing of red blood cells (RBCs) when suspended in blood plasma flowing through square cross-section capillary tubes. RBCs are known to be highly deformable, and the plasma contains various polymers (approximately 8% by volume). The face-on image of the tube cross-section near the outlet was taken from the downstream side using a high-speed camera, enabling accurate positions of RBC centroids in the cross-section to be obtained. At low flow rates, RBCs were observed to accumulate near the tube centerline, whereas increasing the flow rates caused RBCs to focus near four points located on the diagonal of the downstream cross-section. This focusing behavior significantly contrasts with that of the comparably sized rigid particles. Additional experiments using glutaraldehyde-hardened RBCs confirmed that the RBC focusing on the diagonal is primarily attributed to RBC deformability. A slight contribution of plasma elasticity was also suggested by the difference between the distributions of spherical particles suspended in plasma and those in Newtonian fluids. Based on the experimental results, the properties of deformability- and elasticity-induced lifts were discussed.

（written by M. Sugihara-Seki on behalf of all authors.）

In quantum mechanics textbooks, a node-less wave function is described as having lower energy than that with nodal planes, because the kinetic energy increases with an increasing number of nodes. This statement has been thought to be universal.

However, we have recently found an exceptional case in the decavacancy of Si crystal, where node-less mixing of four dangling-bond orbitals (φ_{A}, φ_{B}, φ_{C}, and φ_{D}) in the singlet state leads to a higher energy than node-full mixing in the triplet states. That is,

(1)

where

(2)

(+φ_{A} -φ_{B }-φ_{C }+φ_{D})/2,

(+φ_{A}-φ_{B }+φ_{C }-φ_{D})/2.

This unexpected energy ordering is the *enigma* discussed and solved in our study.

Decavacancy V_{10}. is one of the magic number vacancies, obtained by removing a Si_{10 }cluster from an otherwise perfect Si crystal. Although the vacancy is accompanied by 16 dangling bonds, 12 of them are re-bonded with adjacent ones. Thus, we have only four dangling bonds remaining in V_{10}. The four dangling-bond orbitals (φ_{A}, φ_{B}, φ_{C}, and φ_{D}) are arranged under the T* _{d}* symmetry, which mix to generate the singlet and triplet electron states in the band gap, as described by Eq. (2). Our finding in Eq. (1) is surprising, because it seems to contradict a universal rule stated in the textbooks.

To clarify the underlying physics, we constructed a model to reproduce the energy ordering in Eq. (1), and successfully showed that such a non-intuitive electronic structure originates from the slight hybridization of the four dangling-bond states in the band gap with the 12 re-bond states outside the band gap. Here, the “re-bond states” refers to the six bonding states in the valence band and the six anti-bonding states in the conduction band, generated when 12 dangling bonds are paired with adjacent ones. Although such pairing makes the rebond states inactive, we found that the passivation was not perfect. They are slightly hybridized with the four dangling-bond states in the band gap, which make the energy of the node-less singlet higher than that of the node-full triplet.

We argue that this peculiar electronic structure is reflected in the Jahn-Teller instability of the system. We also note that large-scale DFT calculations are paramount for this work, because the supercell size must be large enough for the results of calculations to converge into Eq. (1).

(Written by K. Uchida on behalf of all authors.)

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