We have examined the superconducting ground-state properties of the caged-type compound ${\mathrm{Sc}}_5{\mathrm{Rh}}_6{\mathrm{Sn}}_{18}$ using magnetization, heat capacity, and muon-spin relaxation or rotation $\left(\mu \mathrm{SR}\right)$ measurements. Magnetization measurements indicate type-II superconductivity with an upper critical field of ${\mu }_0{H}_{c2}\left(0\right)=7.24\mathrm{T}$. The zero-field-cooled and field-cooled susceptibility measurements unveil the onset of a diamagnetic signal below $T_{\mathbf{c}}=4.4\mathrm{K}$. The interpretation of the heat-capacity results below $T_{\mathbf{c}}$ using the $\alpha \text{−}\mathrm{BCS}$ model unveils the value of $\alpha =2.65$, which gives the dimensionless ratio $2\mathrm{\Delta }\left(0\right)/k_B{T}_{\mathbf{c}}=5.3$, intimating that ${\mathrm{Sc}}_5{\mathrm{Rh}}_6{\mathrm{Sn}}_{18}$ is a strong-coupling BCS superconductor. The zero-field $\mu \mathrm{SR}$ measurements in the longitudinal geometry exhibit a signature of the spontaneous appearance of the internal magnetic field below the superconducting transition temperature, indicating that the superconducting state is characterized by the broken time-reversal symmetry (TRS). We have compared the results of broken TRS in ${\mathrm{Sc}}_5{\mathrm{Rh}}_6{\mathrm{Sn}}_{18}$ with that observed in $R_5{\mathrm{Rh}}_6{\mathrm{Sn}}_{18}(R=\mathrm{Lu}$ and Y).

To give a general description of the influences of electric fields or currents on magnetization dynamics, we developed a semiclassical theory for the magnetization implicitly coupled to electronic degrees of freedom. In the absence of electric fields, the Bloch electron Hamiltonian changes the Berry curvature, the effective magnetic field, and the damping in the dynamical equation of the magnetization, which we classify into intrinsic and extrinsic effects. Static electric fields modify these as first-order perturbations, with which we were able to give a physically clear interpretation of the current-induced spin-orbit torques. We used a toy model mimicking a ferromagnet-topological-insulator interface to illustrate the various effects, and we predicted an anisotropic gyromagnetic ratio and the dynamical stability for an in-plane magnetization. Our formalism can also be applied to the slow dynamics of other order parameters in crystalline solids.

A spin-fermion model that captures the charge-transfer properties of Cu-based high critical temperature superconductors is introduced and studied via Monte Carlo simulations. The strong Coulomb repulsion among $d$ electrons in the Cu orbitals is phenomenologically replaced by an exchange coupling between the spins of the itinerant electrons and localized spins at the Cu sites, formally similar to double-exchange models for manganites. This interaction induces a charge-transfer insulator gap in the undoped case (five electrons per unit cell). Adding a small antiferromagnetic Heisenberg coupling between localized spins reinforces the global tendency towards antiferromagnetic order. To perform numerical calculations the localized spins are considered classical as in previous related efforts. In this first paper, undoped and doped $8\times 8$ clusters are analyzed in a wide range of temperatures. The numerical results reproduce experimental features in the one-particle spectral function and the density of states, such as: (i) the formation of a Zhang-Rice-like band with a dispersion on the order of $\sim 0.5\mathrm{eV}$ and with rotational symmetry about the wave-vector $(\pi /2,\pi /2)$ at the top of the band and (ii) the opening of a pseudogap at the chemical potential upon doping. We also observed incipient tendencies towards spin incommensurability. This simple model allows for an unbiased study of charge-transfer insulators and offers a formalism intermediate between standard mean-field approximations that fail at finite temperatures in regimes with short-range order and sophisticated quantum Monte Carlo techniques that suffer sign problems.

We investigate a semimetal-superconductor phase transition of two-dimensional Dirac electrons at zero temperature by large-scale and essentially unbiased quantum Monte Carlo simulations for the half-filled attractive Hubbard model on the triangular lattice, in the presence of alternating magnetic $\pi$ flux, that is introduced to construct two Dirac points in the one-particle bands at the Fermi level. This phase transition is expected to describe quantum criticality of the chiral XY class in the framework of the Gross-Neveu model, where, in the ordered phase, the $U\left(1\right)$ symmetry is spontaneously broken and a mass gap opens in the excitation spectrum. We compute the order parameter of the $s$-wave superconductivity and estimate the quasiparticle weight from the long-distance behavior of the single-particle Green's function. These calculations allow us to obtain the critical exponents of this transition in a reliable and accurate way. Our estimate for the critical exponents is in good agreement with those obtained for a transition to a Kekulé valence bond solid, where an emergent $U\left(1\right)$ symmetry is proposed [Z.-X. Li et al., Nat. Commun. 8, 314 (2017)].

In this work we propose a parton state as a candidate state to describe the fractional quantum Hall effect in the half-filled second Landau level. The wave function for this parton state is ${\mathcal{P}}_{\mathrm{LLL}}{\mathrm{\Phi }}_1^3{\left[{\mathrm{\Phi }}_2^{*}\right]}^2\sim {\mathrm{\Psi }}_{2/3}^2/{\mathrm{\Phi }}_1$ and in the spherical geometry it occurs at the same flux as the anti-Pfaffian state. This state has a good overlap with the anti-Pfaffian state and with the ground state obtained by exact diagonalization, using the second Landau level Coulomb interaction pseudopotentials for an ordinary semiconductor such as GaAs. By calculating the entanglement spectrum we show that this state lies in the same phase as the anti-Pfaffian state. A major advantage of this parton state is that its wave function can be evaluated for large systems, which makes it amenable to variational calculations. In the Appendix of this work, we have numerically assessed the validity of another candidate state at filling factor $\nu =\frac{5}{2}$, namely, the particle-hole-symmetric Pfaffian (PH-Pfaffian) state. We find that the proposed candidate wave function for the PH-Pfaffian state is particle-hole symmetric to a high degree but it does not appear to arise as the ground state of any simple Hamiltonian with two-body interactions.

We develop a statistical theory of waveform shaping of incident waves that aims to efficiently deliver energy at weakly lossy targets which are embedded inside chaotic or weakly disordered enclosures such as body cavities, buildings, vessels, etc. Our approach utilizes the universal features of chaotic scattering, thus minimizing the use of information related to the exact characteristics of the chaotic enclosure. The proposed theory applies equally well to systems with and without time-reversal symmetry and will find applications in diverse areas of applied physics involving wave-front shaping for targeted energy transfer in complex environments.

A higher-order topological insulator (HOTI) is an extended notion of the conventional topological insulator. It belongs to a special class of topological insulators to which the conventional bulk-boundary correspondence is not applicable. Provided the mirror symmetries are present, the bulk topological number is described by the quantized Wannier center located at a high-symmetry point of the crystal. The emergence of corner states is a manifestation of nontrivial topology in the bulk. In this paper we propose minimal models for the Wannier-type second-order topological insulator in two dimensions and the third-order topological insulator in three dimensions. They are anisotropic chiral-symmetric two-band models. It is explicitly shown that the Wannier center is identical to the winding number in the present model, demonstrating that it is indeed a topological quantum number. Finally we point out that the essential physics of phosphorene near the Fermi energy is described by making a perturbation of the Wannier-type HOTI. We predict that these corner states will be observed in the rhombus structure of phosphorene near the Fermi energy around $-0.16\mathrm{eV}$.

The ${\mathrm{HfV}}_2{\mathrm{Ga}}_4$ compound was recently reported to exhibit unusual bulk superconducting properties, with the possibility of multiband behavior. To gain insight into its properties, we performed ab initio electronic-structure calculations based on the density functional theory (DFT). Our results show that the density of states at the Fermi energy is mainly composed by V-$d$ states. The McMillan formula predicts a superconducting critical temperature $\left(T_c\right)$ of approximately 3.9 K, in excellent agreement with the experimental value at 4.1 K, indicating that superconductivity in this new compound may be explained by the electron-phonon mechanism. Calculated valence charge density maps clearly show directional bonding between Hf and V atoms with 1D highly populated V chains and some ionic character between Hf-Ga and V-Ga bonds. Finally, we have shown that there are electrons occupying two distinct bands at the Fermi level, with different characters, which supports experimental indications of possible multiband superconductivity. Based on the results, we propose the study of a related compound, ${\mathrm{ScV}}_2{\mathrm{Ga}}_4$, showing that it has similar electronic properties, but probably with a higher $T_c$ than ${\mathrm{HfV}}_2{\mathrm{Ga}}_4$.

The integration of room-temperature ferromagnetic thin film on ferroelectric substrate with strong magnetoelastic coupling provides a new pathway to tune and improve their functionality for device-application purposes. Epitaxial thin film of ferromagnetic ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}\mathrm{Mn}{\mathrm{O}}_3$ (LSMO) on single-crystalline $\mathrm{BaTi}{\mathrm{O}}_3$ (BTO) substrate is observed to be magnetoelastically coupled with BTO substrate with electric-field tunability. The coupling is manifested by discontinuous changes in magnetization as well as in resistivity as BTO undergoes the successive structural phase transitions with temperature. The sign of these abrupt changes shows magnetic-field dependency and is attributed to the in-plane switching of the symmetry of magnetic anisotropy via modification in epitaxial strain-induced distortion as BTO crosses the phase-transition temperature. Under the application of electric field, large magnetization changes are observed via the strain-mediated converse magnetoelectric effect in the LSMO/BTO heterostructure. Up to 55% coercivity change ($\mathrm{\Delta }H/H$) and 36% change in squareness ($M_r/M_s$) of loop are achieved via 8 kV/cm electric field at 210 K. Linear dichroism experiments at the O $K$ edge also show the in-plane orbital anisotropy arising because of the presence of (a, c) stripe domains transferred via pseudomorphic growth on BTO.

Calcium and magnesium carbonates are believed to be the host compounds for most of the oxidized carbon in the Earth's mantle. Here, using the evolutionary crystal structure prediction method uspex, we systematically explore the $\mathrm{MgO}\text{−}{\mathrm{CO}}_2$ and $\mathrm{CaO}\text{−}{\mathrm{CO}}_2$ systems at pressures ranging from 0 to 160 GPa to search for thermodynamically stable magnesium and calcium carbonates. While ${\mathrm{MgCO}}_3$ is the only stable magnesium carbonate, three calcium carbonates are stable under pressure: well-known ${\mathrm{CaCO}}_3$, and previously unknown ${\mathrm{Ca}}_3{\mathrm{CO}}_5$ and ${\mathrm{CaC}}_2{\mathrm{O}}_5$. ${\mathrm{Ca}}_3{\mathrm{CO}}_5$ polymorphs are found to contain isolated orthocarbonate ${{\mathrm{CO}}_4}^{4-}$ tetrahedra, and are stable at relatively low pressures $\left(>11\mathrm{GPa}\right)$, whereas ${\mathrm{CaC}}_2{\mathrm{O}}_5$ is stable above 33 GPa and its polymorphs feature polymeric motifs made of ${\mathrm{CO}}_4$ tetrahedra. Detailed analysis of the chemical stability of ${\mathrm{CaCO}}_3,{\mathrm{Ca}}_3{\mathrm{CO}}_5$, and ${\mathrm{CaC}}_2{\mathrm{O}}_5$ in the environment typical of the Earth's lower mantle reveals that none of these compounds can exist in the Earth's lower mantle. Instead, ${\mathrm{MgCO}}_3$ is the main host of oxidized carbon throughout the lower mantle.

The role of external magnetic fields is often neglected in the field of ultrafast magnetization dynamics induced by femtosecond laser pulses. Here it is shown theoretically that very high magnetic fields can substantially modify ultrafast magnetization dynamics at elevated temperatures. Magnetic fields speed up the ultrafast magnetization dynamics. Notably, we predict that the observed two-step demagnetization dynamics in some materials transition to one-step demagnetization dynamics for high magnetic fields. The description of the dynamics is based on the Landau-Lifshitz-Bloch equation of motion. Analytical expressions for the longitudinal and transversal magnetization relaxation time as a function of the magnetic field are provided.

The Kitaev model exhibits a quantum spin liquid hosting emergent fractionalized excitations. We study the Kitaev model on the honeycomb lattice coupled to a magnetic field along the [111] axis. Utilizing large-scale matrix product-based numerical models, we confirm three phases with transitions at different field strengths depending on the sign of the Kitaev exchange: a non-Abelian topological phase at low fields, an enigmatic intermediate regime only present for antiferromagnetic Kitaev exchange, and a field-polarized phase. For the topological phase, we numerically observe the expected cubic scaling of the gap and extract the quantum dimension of the non-Abelian anyons. Furthermore, we investigate dynamical signatures of the topological and the field-polarized phase using a matrix product operator-based time evolution method.

Krausser et al. [Phys. Rev. B 95, 104203 (2017)] present an analysis of the fragility parameter derived from their model for the temperature dependence of the viscosity. The model equation for the isobaric fragility predicts a power-density scaling law under pressure because of its mathematical similarity to the equation resulting from the latter. Comparing both formulas we established the simple relationship between the lambda parameter λ from Krausser, Samwer, and Zaccone (KSZ) and the density scaling exponent γ. Thus, one can easily determine the value of λ from γ. However, using the reported value of the density scaling exponent for commonly known glass formers, we are not able to achieve a satisfactory description of the experimental data. Therefore KSZ are not consistent with the experimental power density scaling.

In this Reply, we discuss the differences between physical parameters used in the derivation of the Krausser-Samwer-Zaccone model of viscosity and those used in the justification of the empirical power-density scaling for repulsive power-law fluids. These fundamental differences preclude a direct combination of the two approaches.

Bulk crystals of electron-doped cuprates with a $T^{\prime }$-type structure require both Ce substitutions and reduction annealing for the emergence of superconductivity while reduction annealing alone can induce superconductivity in thin films of $T^{\prime }$-type cuprates. In order to reveal the low-energy electronic states which are responsible for the superconductivity, we have conducted angle-resolved photoemission spectroscopy measurements on thin films of the superconducting Ce-free $T^{\prime }$-type cuprate ${\mathrm{Pr}}_2{\mathrm{CuO}}_4$. The results indicate that the overall band structure and the Fermi surface area of the superconducting ${\mathrm{Pr}}_2{\mathrm{CuO}}_4$ are similar to those of superconducting Ce-doped bulk single crystals, highlighting the importance of the actual electron concentration rather than the Ce concentration when discussing the physical properties of $T^{\prime }$-type cuprates.

Neutron spectroscopy was applied to study the magnetic interactions of orbitally degenerate ${\mathrm{Co}}^{2+}$ on a host MgO rocksalt lattice where no long-range spin or orbital order exists. The paramagnetic nature of the substituted monoxide ${\mathrm{Co}}_{0.03}{\mathrm{Mg}}_{0.97}\mathrm{O}$ allows for the disentanglement of spin exchange and spin-orbit interactions. By considering the prevalent excitations from ${\mathrm{Co}}^{2+}$ spin pairs, we extract seven exchange constants out to the fourth coordination shell. An antiferromagnetic next-nearest-neighbor ${180}^{\circ }$ exchange interaction is dominant; however, dual ferromagnetic and antiferromagnetic interactions are observed for pairings with other pathways. These interactions can be understood in terms of a combination of orbital degeneracy in the $t_{2g}$ channel and the Goodenough-Kanamori-Anderson rules. Our work suggest that such a hierarchy of exchange interactions exists in transition-metal-based oxides with a $t_{2g}$ orbital degeneracy.

At the interface between a nonmagnetic metal (NM) and a ferromagnetic insulator (FI) spin current can interact with the magnetization, leading to a modulation of the spin current. The interfacial exchange field at these FI-NM interfaces can be probed by placing the interface in contact with the spin transport channel of a lateral spin valve (LSV) device and observing additional spin relaxation processes. We study interfacial exchange field in lateral spin valve devices where a Cu spin transport channel is in proximity with ferromagnetic insulator EuS (EuS-LSV) and yttrium iron garnet ${\mathrm{Y}}_3{\mathrm{Fe}}_5{\mathrm{O}}_{12}$ (YIG-LSV). The spin signals were compared with reference lateral spin valve devices fabricated on nonmagnetic Si/${\mathrm{SiO}}_2$ substrate with MgO or ${\mathrm{AlO}}_x$ capping. The nonlocal spin valve signal is about 4 and 6 times lower in the EuS-LSV and YIG-LSV, respectively. The suppression in the spin signal has been attributed to enhanced surface spin-flip probability at the Cu-EuS (or Cu-YIG) interface due to an interfacial spin-orbit field. Besides spin signal suppression we also found a widely observed low temperature peak in the spin signal at $T\sim 30$ K is shifted to higher temperature in the case of devices in contact with EuS or YIG. Temperature dependence of the spin signal for different injector-detector distances reveal fluctuating exchange field at these interfaces cause additional spin decoherence which limit spin relaxation time in addition to conventional sources of spin relaxation. Our results show that temperature-dependent measurement with pure spin current can be used to probe interfacial exchange field at the ferromagnetic insulator-nonmagnetic metal interface.

We study two-dimensional fermions with a short-range interaction in the presence of a Van Hove singularity. It is shown that this system can be consistently described by an effective field theory whose Fermi surface is subdivided into regions as defined by a factorization scale, and that the theory is renormalizable in the sense that all of the counterterms are well defined in the IR limit. The theory has the unusual feature that the renormalization-group equation for the coupling has an explicit dependence on the renormalization scale, much as in theories of Wilson lines. In contrast to the case of a round Fermi surface, there are multiple marginal interactions with nontrivial RG flow. The Cooper instability remains strongest in the BCS channel. We also show that the marginal Fermi-liquid scenario for the quasiparticle width is a robust consequence of the Van Hove singularity. Our results are universal in the sense that they do not depend on the detailed properties of the Fermi surface away from the singularity.

The search of new means of generating and controlling topological states of matter is at the front of many joint efforts, including band-gap engineering by doping and light-induced topological states. Most of our understading, however, is based on a single particle picture. Topological states in systems including interaction effects, such as electron-electron and electron-phonon, remain less explored. By exploiting a nonperturbative and nonadiabatic picture, here we show how the interaction between electrons and a coherent phonon mode can lead to a band gap hosting edge states of topological origin. Further numerical simulations witness the robustness of these states against different types of disorder. Our results contribute to the search of topological states, in this case in a minimal Fock space.