Fractional quantum Hall (FQH) fluids host quasiparticle excitations that carry a fraction of the electronic charge. Moreover, in contrast to bosons and fermions that carry exchange statistics of 0 and $\pi$ respectively, these quasiparticles of FQH fluids, when braided around one another, can accumulate a Berry phase, which is a fractional multiple of $\pi$. Deploying the spherical geometry, we numerically demonstrate that composite fermion particle (CFP) excitations in the Jain FQH states carry Abelian fractional statistics. Previously, the exchange statistics of CFPs were studied in the disk geometry, where the statistics get obscured due to a shift in the phase arising from the addition of another CFP, making its determination cumbersome without prior knowledge of the shift. We show that on the sphere this technical issue can be circumvented and the statistics of CFPs can be obtained more transparently. The ideas we present can be extended to determine the statistics of quasiparticles arising in certain non-Abelian partonic FQH states.

We develop a diagrammatic perturbation theory to account for the emergence of moiré bands in the continuum model of twisted bilayer graphene. Our framework is build on treating the moiré potential as a perturbation that transfers electrons from one layer to another through the exchange of the three wave vectors that define the moiré Brillouin zone. By working in the two-band basis of each monolayer, we analyze the one-particle Green's function and introduce a diagrammatic representation for the scattering processes. We then identify the moiré-induced self-energy, relate it to the quasiparticle weight and velocity of the moiré bands, and show how it can be obtained by summing irreducible diagrams. We also connect the emergence of flat bands to the behavior of the static self-energy at the magic angle. In particular, we show that a vanishing Dirac velocity is a direct consequence of the relative orientation of the momentum transfer vectors, suggesting that the origin of magic angles in twisted bilayer graphene is intrinsically connected to its geometrical properties. Our approach provides a diagrammatic framework that highlights the physical properties of the moiré bands.

We present a high-pressure single-crystal x-ray structure analysis of two-dimensional layered $1T\text{−}{\mathrm{VSe}}_2$, which is known to undergo an incommensurate charge density wave transition at 110 K at ambient pressure. When pressure is applied to $1T\text{−}{\mathrm{VSe}}_2$ at 150 K, a structural phase transition appears at about 8 GPa. The structural analysis of x-ray diffraction data obtained from a single crystal sample, with the correct corrections for the use of a diamond anvil cell and taking into account the effects of multiple domains, using only the superlattice peaks, reveals the appearance of “ribbon chain” type vanadium clusters at a high-pressure region. The formation of Se-Se bonds under high pressure and the associated unexpected charge injection into vanadium are largely responsible for the formation of ribbon-chain clusters. We discuss the possibility that such interanion bond formation occurs universally in the high-pressure phase of transition metal diserenides.

In this Letter, we investigate the electronic structure of a spin-triplet superconductor candidate ${\mathrm{CeRh}}_2{\mathrm{As}}_2$ using high-resolution angle-resolved photoemission spectroscopy and density functional theory calculations. Notably, possible Fermi surface nesting hints at connections to magnetic excitation or quadrupole density wave phenomena, elucidating the superconducting mechanisms. Measured band structures reveal primarily localized $4f$ electrons, with minor itinerant contributions. Additionally, a transition from localized to itinerant behavior and significant $c\text{−}f$ hybridization anisotropy underscore the role of $f$ electrons in shaping electronic properties. These findings deepen our understanding of ${\mathrm{CeRh}}_2{\mathrm{As}}_2$'s unconventional superconductivity and magnetism. Further exploration promises advances in superconductivity research.

We propose a measurement-producing hierarchy emerging among correlated states by sequential subsystem projective measurements. We start from symmetry-protected-topological (SPT) cluster states with a large symmetry and apply sequential subsystem projective measurements to them and find that generalized cluster SPT states with a reduced symmetry appear in the subsystem of the unmeasured sites. That prescription finally produces Greenberger-Horne-Zeilinger states with long-range order in the subsystem composed of periodic unmeasured sites of the original lattice. The symmetry-reduction hierarchical structure from a general large-symmetric SPT cluster state is clearly captured by the measurement update flow in the efficient algorithm of stabilizer formalism. This approach is useful not only for the analytical search for the measured state, but also for numerical simulation with a large system size. We also numerically verify the symmetry-reduction hierarchy by sequential subsystem projective measurements applied to large systems and large-symmetric cluster SPT states.

The rare-earth tritellurides have a rich phase diagram that includes charge density waves (CDWs), superconductivity, and magnetic order, offering a platform to study the interplay between these phases on a square-net system. Prior studies have shown that defects can affect the CDW characteristics in these materials, yet coupling between the CDW order and the underlying microstructure has not been studied at the nanoscale. Here we use scanning transmission electron microscopy at cryogenic temperatures to directly visualize the effects of defects on the CDW order and provide a spatially resolved microscopic correlation between the CDW transition and structural defects. We show that in the presence of extended defects, such as dislocations and stacking faults, the weak orthorhombicity of the rare-earth tritellurides is lost and the material becomes pseudotetragonal. Since the orthorhombicity acts as a symmetry breaking field for the CDW transitions in rare-earth tritellurides, the presence of these extended defects modulates the energetics of the CDWs and suppresses the ground-state CDW phase at low temperature.

We investigate the role of the spectral dimension $d_s$ in determining the universality of phase transitions on a complex network. Due to its structural heterogeneity, a complex network generally acts as a disordered system. Specifically, we study the synchronization and entrainment transitions in the nonequilibrium dynamics of the Kuramoto model and the phase transition of the equilibrium dynamics of the classical $XY$ model, thereby covering a broad spectrum from nonlinear dynamics to statistical and condensed matter physics. Using linear theory, we obtain a general relationship between the dynamics occurring on the network and the underlying network properties. This yields the lower critical spectral dimension of the phase synchronization and entrainment transitions in the Kuramoto model as $d_s=4$ and $d_s=2$, respectively, whereas for the phase transition in the $XY$ model it is $d_s=2$. To test our theoretical hypotheses, we employ a network where any two nodes on the network are connected with a probability proportional to a power law of the distance between the nodes; this realizes any desired $d_s\in [1,\infty )$. Our detailed numerical study agrees well with the prediction of linear theory for the phase synchronization transition in the Kuramoto model. However, it shows a clear entrainment transition in the Kuramoto model and phase transition in the $XY$ model at $d_s\gtrsim 3$, not $d_s=2$ as predicted by linear theory. Our study indicates that network disorder in the region $2\le d_s\lesssim 3$ introduces strong finite-size fluctuations, which makes it extremely difficult to probe the existence of the ordered phase as predicted, affecting the dynamics profoundly.

High-resolution transmission electron microscopy and superconducting quantum interference device magnetometry shows that epitaxial CuMnSb films exhibit a coexistence of two magnetic phases, coherently intertwined in nanometric scales. The dominant $\alpha$ phase is half-Heusler cubic antiferromagnet with the Néel temperature of 62 K, the equilibrium structure of bulk CuMnSb. The secondary phase is its ferromagnetic tetragonal $\beta$ polymorph with the Curie temperature of about 100 K. First principles calculations provide a consistent interpretation of experiment, since (i) total energy of $\beta –\mathrm{CuMnSb}$ is higher than that of $\alpha –\mathrm{CuMnSb}$ only by 0.12 eV per formula unit, which allows for epitaxial stabilization of this phase, (ii) the metallic character of $\beta –\mathrm{CuMnSb}$ favors the Ruderman-Kittel-Kasuya-Yoshida ferromagnetic coupling, and (iii) the calculated effective Curie-Weiss magnetic moment of Mn ions in both phases is about $5.5{\mu }_{\mathrm{B}}$, favorably close to the measured value. Calculated properties of all point native defects indicate that the most likely to occur are ${\mathrm{Mn}}_{\mathrm{Cu}}$ antisites. They affect magnetic properties of epilayers, but they cannot induce the ferromagnetic order in CuMnSb. Combined, the findings highlight a practical route towards fabrication of functional materials in which coexisting polymorphs provide complementing functionalities in one host.

We theoretically investigated the antivortex stabilized by anisotropic Dzyaloshinskii-Moriya interaction (DMI) in nanodisks. Remarkably, we found that the antivortex remains stable even when the nanodisk radius is reduced to 15 nm. We also investigated the antivortex dynamics under a static in-plane magnetic field, which shows that the displacement of the antivortex core depends on its vorticity and helicity, providing a fundamental basis for distinguishing different vortex types. Additionally, spin-polarized currents can trigger a self-sustained gyration of the antivortex at low current densities, while inducing polarity switching at high current densities. Our findings offer valuable insights into the role of DMI in stabilizing topological solitons and their potential applications in spin-torque nano-oscillators and magnetic memories.

It is theoretically found that in-plane vortices may exist in a thin normal metal (N) layer (with thickness $d_N$ much smaller than the coherence length ${\xi }_N$) that covers a superconductor (S). Vortices enter the N layer with proximity-induced superconductivity at a sufficiently large in-plane magnetic field. These vorticies have squeezed cores and are located (pinned) near the SN interface. At large magnetic fields, we find a nascent vortex state, which is a spatially modulated state along the finite length N layer with zero vorticity. This state does not exist in a finite length single S layer.

The field-free and highly efficient diodes with the nonreciprocity of supercurrent are believed to be the core block of superconducting computing devices without dissipation. In this paper, we propose a Josephson diode based upon altermagnets with vanishing net macroscopic magnetization. The nonreciprocity of supercurrent can be realized without applying any external magnetic field or ferromagnetic exchange field, which can avoid the magnetic cross-talk between the basic elements of the devices. A high efficiency exceeding $40\%$ can be obtained, and the efficiency shows high stability when the structure parameters are changed. The diode efficiency is antisymmetric about the relative orientation angle of the superconducting leads, so that its sign can easily be inverted by adjusting the relative orientation angle. The symmetries satisfied by the current-phase difference relations and the diode efficiency are analyzed by considering the transformations of the junctions under the time reversal, the spin rotation, and the mirror reflection operations. The high efficiency and the high stability of the Josephson diode effect in our junctions make it possible to design field-free dissipationless diode devices.

Single crystals of $X{\mathrm{Pt}}_5\text{P}$ ($X$ = Al, Ga, and In), belonging to the 1-5-1 family of compounds, were grown from a Pt-P solution at high temperatures, and measurements of the ambient pressure, temperature-dependent magnetization, resistivity, and x-ray diffraction were made. Additionally, the ambient-pressure Hall resistivity and temperature-dependent resistance under pressure were measured on ${\mathrm{GaPt}}_5\text{P}$. All three compounds have a tetragonal $P4/mmm$ crystal structure at room temperature with metallic transport and weak diamagnetism over the 2–300 K temperature range. Surprisingly, at ambient pressure, both the transport and magnetization measurements on ${\mathrm{GaPt}}_5\text{P}$ show a steplike feature in the 70–90 K region, suggesting a possible structural phase transition. Neither ${\mathrm{AlPt}}_5\text{P}$ nor ${\mathrm{InPt}}_5\text{P}$ have any signatures of a phase transition in their temperature-dependent electrical resistance and magnetization data. Both the hysteretic nature and sharpness of the features in the ${\mathrm{GaPt}}_5\text{P}$ data suggest that the transition is first-order. Single-crystal x-ray diffraction measurements provided further details of the structural transition with a possibility of a crystal symmetry different from $P4/mmm$ below the transition temperature. The transition is characterized by anisotropic changes in the lattice parameters and a volume collapse with respect to the high-temperature tetragonal crystal structure. Furthermore, satellite peaks are observed at two distinct and nonequivalent wave vectors (0, 0, 0.5) and (0.5, 0.5, 0.5), and density functional theory calculations present phonon softening, especially at (0.5, 0.5, 0.5), as a possible driving mechanism. Additionally, we find that the structural transition temperature increases rapidly with increasing pressure, reaching room temperature by $\sim 2.2$ GPa, highlighting the high degree of pressure sensitivity of ${\mathrm{GaPt}}_5\text{P}$ and fragile nature of its room-temperature structure. Even though the volume collapse and extreme pressure sensitivity suggest chemical pressure should drive a similar structural change in ${\mathrm{AlPt}}_5\text{P}$, where both unit-cell dimensions and volume are smaller, its structure is found to be the same as that of the room-temperature ${\mathrm{GaPt}}_5\text{P}$. Overall, ${\mathrm{GaPt}}_5\text{P}$ stands out as a sole member of the 1-5-1 family of compounds for which a temperature-driven structural change has been observed.

Multiferroic tunneling junctions (MFTJs), which comprise magnetic electrodes and extremely thin ferroelectric tunneling barriers, are promising contenders for nonvolatile memory applications. Noncollinear antiferromagnetic ${\mathrm{Mn}}_3\mathrm{Sn}$ with time-reversal symmetry-breaking polarization properties and ferroelectric $\alpha \text{−}{\mathrm{In}}_2{\mathrm{Se}}_3$ may open up the possibility of constructing room-temperature MFTJs. In this study, we investigate the spin-correlation transport in the MFTJs with ${\mathrm{Mn}}_3\mathrm{Sn}/\mathrm{BN}/\alpha \text{−}{\mathrm{In}}_2{\mathrm{Se}}_3/{\mathrm{Mn}}_3\mathrm{Sn}$ structure using first-principles calculations. The resistance in this structure can be manipulated by tuning the directions of both the Néel vector of ${\mathrm{Mn}}_3\mathrm{Sn}$ and the electric polarization of the $\alpha \text{−}{\mathrm{In}}_2{\mathrm{Se}}_3$ layer. Thus, multiple tunneling resistive states can be realized. We predict that huge tunneling magnetoresistance up to 6650% can be obtained by switching the magnetically oriented Néel vectors of ${\mathrm{Mn}}_3\mathrm{Sn}$, and more than 8000% tunneling electrical resistance can be obtained by controlling the ferroelectric structure of $\alpha \text{−}{\mathrm{In}}_2{\mathrm{Se}}_3$. Our work underscores the potential applications of ${\mathrm{Mn}}_3\mathrm{Sn}$ in multiferroic nonvolatile memories and lays the foundation for the development of ultrafast and efficient spintronic devices utilizing antiferromagnets.

Open quantum systems display unusual phenomena not seen in closed systems, such as new topological phases and unconventional phase transitions. An interesting example was studied for a quantum spin liquid in the Kitaev model [Phys. Rev. Lett. 126, 077201 (2021)]; an effective non-Hermitian Kitaev model, which incorporates dissipation effects, was shown to give rise to a gapless spin liquid state with exceptional points in the Majorana dispersions. Given that an external magnetic field induces a gapped Majorana topological state in the Hermitian case, the exceptional points may bring about intriguing quantum phenomena under a magnetic field. Here we investigate the non-Hermitian Kitaev model perturbed by a magnetic field. We show that the exceptional points remain gapless up to a nonzero critical magnetic field, in stark contrast with the Hermitian case where an infinitesimal field opens a gap. The gapless state is stable over a wide range of the magnetic field for some particular parameter sets, and, in special cases, undergoes topological transitions to another gapless state with different winding number around the exceptional points without opening a gap. In addition, in the system with edges, we find that the non-Hermitian skin effect is induced by the magnetic field, even for the parameters where the skin effect is absent at zero field. The chirality of edge states is switched through the exceptional points, similarly to the surface Fermi arcs connected by the Weyl points in three-dimensional Weyl semimetals. Our results provide a new possible route to stabilize topological gapless quantum spin liquids under the magnetic field in the presence of dissipation.

The spin-1 triangular lattice Heisenberg antiferromagnet $\mathrm{C}{\mathrm{a}}_3\mathrm{NiN}{\mathrm{b}}_2{\mathrm{O}}_9$ and its sister compounds are conjectured to promote the formation of many-body quantum entangled states such as a quantum spin liquid (QSL), an exotic phase which features fractionalized quasiparticle excitations and emergent gauges. We probe the single crystal of $\mathrm{C}{\mathrm{a}}_3\mathrm{NiN}{\mathrm{b}}_2{\mathrm{O}}_9$ using an in-depth Raman spectroscopic technique. Our measurements provide evidence for the fractionalized excitations, suggesting that the current system is in close proximity to the QSL phase. This is also in line with the proposed higher-order fractional magnetization plateau in this system, as these plateaus have an intricate relationship with the spin entanglement. We observed unconventional underlying scattering as a broad continuum with an intensity that shows fermionic statistics. Additionally, phonon modes show Fano asymmetry, also conjectured as a fingerprint of the spin-liquid phase, and above a critical Raman shift also show fermionic statistics in their intensity evolution.

The Anderson-Higgs mode in a superconductor corresponds to a collective and coherent oscillation of the order parameter amplitude. We propose to detect this mode in a tunnel Josephson junction between two singlet $s$-wave diffusive superconductors in presence of a THz external irradiation at angular frequency $\omega$. By solving the Keldysh-Usadel equations, we obtain that the current-voltage relation exhibits a series of peaks of which only a subset is enhanced by the Anderson-Higgs mode. Furthermore, at zero bias, the junction features an ac current oscillating at $2\omega$, which is resonant when $\hslash \omega$ hits the superconducting gap, thereby indicating the activation of the Anderson-Higgs mode.

In graphene, the approximate SU(4) symmetry associated with the spin and valley degrees of freedom in the quantum Hall (QH) regime is reflected in the fourfold degeneracy of graphene's Landau levels (LLs). Interactions and the Zeeman effect break such approximate symmetry and lift the corresponding degeneracy of the LLs. We study how the breaking of the approximate SU(4) symmetry affects the properties of graphene's QH edge modes located in proximity to a superconductor. We show how the lifting of the fourfold degeneracy qualitatively modifies the transport properties of the QH-superconductor heterojunction. For the zero LL, by placing the edge modes in proximity to a superconductor, it is, in principle, possible to realize a 1D topological superconductor supporting Majoranas in the presence of sufficiently strong Zeeman field. We estimate the topological gap of such a topological superconductor and relate it to the properties of the QH-superconductor interface.

The unfilled skutterudite $\mathrm{Co}{\mathrm{P}}_3$ hosts extremely large magnetoresistance (∼2 × ${10}^4\%$ at 30 T and 2 K), large hole mobility (∼2 × ${10}^4 \mathrm{c}{\mathrm{m}}^2{\mathrm{V}}^{-1}{\mathrm{s}}^{-1}$, 2 K), and a fourfold quadratic contact point (QCP) above the Fermi level in the electronic structure. We unveil herein that the partial filling of Eu onto the icosahedral void sites of $\mathrm{Co}{\mathrm{P}}_3$ can shift the QCP to lie below the Fermi level while retaining the high carrier mobility (∼1.6 × ${10}^4 \mathrm{c}{\mathrm{m}}^2{\mathrm{V}}^{-1}{\mathrm{s}}^{-1}$, 2 K). Unlike nonmagnetic $\mathrm{Co}{\mathrm{P}}_3$, partially filled skutterudite ${\mathrm{Eu}}_{0.412}{\mathrm{Co}}_4{\mathrm{P}}_{12}$ is a soft ferromagnet with almost isotropic magnetism. Additionally, an intriguing topological Hall effect is observed, likely hinting an unusual spin texture. In this paper, we provide useful insights into the interplay between magnetism and the nontrivial feature of the electronic band structure, which would guide more efforts in studying this issue.

Anapole electrodynamics is now a rapidly developing area of nonradiating and invisible systems like metamaterials, nanoparticles, and even toroidal optical transitions in hydrogenlike atoms from microwaves to optics. The main advantages are demonstrated strong localized near fields and an extremely high $Q$ factor due to the absence of radiating losses. In this paper, we expand the field of anapole electrodynamics to the quantum area and demonstrate the anharmonicity of a superconducting meta-atom with an embedded Josephson junction. The maximum dimension of meta-atoms is 6 mm, and it works in the microwave range. The microwave single- and two-tone spectroscopic measurements in a dilution cryostat at 20 mK demonstrate three transition energy levels: single-photon and two-photon transitions. Moreover, we obtain an anharmonicity of 540 kHz, which is very close to 500 kHz obtained in simulations. We show that the anapole meta-atoms are promising candidates for giant qubits for quantum computing applications.

We study entanglement entropy of unusual ${\mathbb{Z}}_N$ topological stabilizer codes which admit fractional excitations with restricted mobility constraint in a manner akin to fracton topological phases. It is widely known that the subleading term of the entanglement entropy of a disk geometry in conventional topologically ordered phases is related to the total number of the quantum dimension of the fractional excitations. We show that, in our model, such a relation does not hold, i.e., the total number of the quantum dimension varies depending on the system size, whereas the subleading term of the entanglement entropy takes a constant number irrespective to the system size. We give a physical interpretation of this result in the simplest case of the model. More thorough analysis on the entanglement entropy of the model on generic lattices is also presented.