It is well established that for diffusive solid-liquid interfaces the interfacial anisotropy arises due to symmetry breaking of density waves at the interface. While the interfacial anisotropy is expected to be related to the underlying lattice symmetry, the anisotropy can still differ among materials with the same lattice structure due to the difference in the interatomic potentials. To shed light on this, a general Ginzburg-Landau (GL) theory of solid-liquid interfaces, based on crystal symmetry and classical density functional theory, is proposed to analytically connect the relation between lattice symmetry, the shape of the free-energy landscape, and surface energy anisotropy. Using a perturbative scheme, we show that the corresponding anisotropic form of the surface energy, depending on crystal symmetry, naturally appears in the perturbation expansion. To explore how the double-well free-energy landscape in the GL theory affects the anisotropy, we consider lattices of hexagonal symmetry as an example, for which the shape of the free-energy landscape is shown to only depend on one parameter. The dependence of anisotropy on the free-energy landscape predicted by the perturbation scheme is shown to be in good agreement with numerical solutions of the GL theory. Finally, a universal relation between density wave profile widths and the anisotropy parameter of the surface energy is proposed and validated using a phase-field crystal method.

Open phononic systems including resonators radiating inside an unbounded medium support localized phonons characterized by a complex frequency. In this context, the concept of elastic quasinormal mode (QNM) arises naturally, as in the cases of nanophotonic and plasmonic open systems. Based on a complex, unconjugated form of reciprocity theorem for elastodynamics, the eigenfunction expansion theorem expressed on the elastic QNM basis yields an accurate approximation to the response function, for an arbitrary excitation. The description of the elastic Purcell effect then requires defining a complex-valued modal volume for each QNM. For validation, we first consider the case a vibrating nylon rod radiating in water. As a second test example, we consider a slender nickel ridge on the surface of a fused silica substrate, before extending our attention to a nanoscale tuning fork composed of two such ridges. In all cases, the response estimated from only a few elastic QNMs agrees with the solution to the elastodynamic equation.

Noncolinear or noncoplanar spin configurations in magnetic materials usually give rise to a fascinating array of physical phenomena. Here, we perform a systematic study of magnetic and electronic transport properties in a noncolinear itinerant magnet ${\mathrm{PrMn}}_2{\mathrm{Ge}}_2$. With the field applied along different directions, ${\mathrm{PrMn}}_2{\mathrm{Ge}}_2$ displays uniaxial magnetic anisotropy with an easy axis along the $c$ axis. Both the temperature-dependent magnetization and longitudinal resistivity reveal an anomaly at 330 K, well corresponding to the magnetic transition of the Mn sublattice from a colinear antiferromagnetic state to a canted ferromagnetic state. Strikingly, ${\mathrm{PrMn}}_2{\mathrm{Ge}}_2$ exhibits anomalous Hall effect (AHE) together with prominent negative magnetoresistivity (MR) when the field is applied along the $c$ axis. The negative MR can be linked to the suppression of spin scattering. Based on the scaling analysis between the anomalous Hall resistivity ${\rho }_{yx}^A$ and longitudinal resistivity ${\rho }_{xx}$, the relationship ${\rho }_{yx}^A\propto {\rho }_{xx}^{1.18}$ has been given, which indicates that the observed AHE in ${\mathrm{PrMn}}_2{\mathrm{Ge}}_2$ is likely dominated by the skew-scattering mechanism. Simultaneously, a sharp jump has been observed in the hysteresis loop, which is also discernible in the field dependence of Hall resistivity and magnetoresistivity. Such features presumably result from the movement of the domain wall.

Precise angle-resolved magnetoresistance (ARMR) measurements in various magnetic fields enabled us to create illustrative distributions of $\mathrm{\Delta }\rho /\rho \left(\phi ,H\right)$ in $\mathrm{Tm}{\mathrm{B}}_4$, where $\phi$ is the angle between the sample $c$ axis and applied magnetic field $H$. These distributions reveal the charge transport anisotropy in this strongly Ising anisotropic quantum antiferromagnet with a geometrically frustrated Shastry-Sutherland lattice exhibiting fractional magnetization plateaus. While in the paramagnetic region $\mathrm{\Delta }\rho /\rho \left(\phi ,H\right)$ reaches its maxima for $H\perp c$, below the Néel temperature $T_N=11.7$ K the situation is different. Here the main MR features appear for $H\parallel c$, i.e., along the easy axis of magnetic anisotropy, and correspond to magnetic phases and phase transitions between them. It is interesting that all the above features (maxima) related with the scattering of conduction electrons on spin magnetic structure are related with fractional magnetization plateaus. With increasing $\phi$ MR anomalies shift to higher fields. Above the field of magnetic saturation, moreover, significant MR maxima have been observed at certain angles which correspond to specific directions in the crystal lattice, pointing to field directions in which the scattering of conduction electrons on the magnetic structure is the highest. Thus, ARMR appears to be a sensitive experimental tool reflecting the angular dependence of the interplay between charge carriers and magnetic structure as a function of temperature and applied magnetic field.

$\mathrm{Eu}{\mathrm{Cd}}_2{\mathrm{P}}_2$ is notable for its unconventional transport: upon cooling the metallic resistivity changes slope and begins to increase, ultimately 100-fold, before returning to its metallic value. Surprisingly, this giant peak occurs at 18 K, well above the Néel temperature ($T_N$) of 11.5 K. Using a suite of sensitive probes of magnetism, including resonant x-ray scattering and magneto-optical polarimetry, we have discovered that ferromagnetic order onsets above $T_N$ in the temperature range of the resistivity peak. The observation of inverted hysteresis in this regime shows that ferromagnetism is promoted by coupling of localized spins and itinerant carriers. The resulting carrier localization is confirmed by optical conductivity measurements.

Theoretical studies of disordered $d$-wave superconductors have focused, with a few exceptions, on optimally doped models with strong scatterers. Addressing recent controversies about the nature of the overdoped cuprates, however, requires studies of the weaker scattering associated with dopant atoms. Here we study simple models of such systems in the self-consistent Bogoliubov-de Gennes (BdG) framework, and compare to disorder-averaged results using the self-consistent $T$-matrix-approximation (SCTMA). Despite surprisingly linear in energy behavior of the low-energy density of states even for quite disordered systems, the superfluid density in such cases retains a quadratic low-temperature variation of the penetration depth, unlike other BdG results reported recently. We trace the discrepancy to smaller effective system size employed in that work. Overall, the SCTMA performs remarkably well, with the exception of highly disordered systems with strongly suppressed superfluid density. We explore this interesting region where gap inhomogeneity dominates measured superconducting properties, and compare with overdoped cuprates.

We characterize the response of a Mott insulating system to a static electric field in terms of its conducting and spectral properties. Dissipation is included by a coupling to fermionic baths and to either optical or acoustic phonons. This paper extends and completes the analysis made in a previous work by the authors [Mazzocchi et al., Phys. Rev. B 106, 125123 (2022)]. In the present work, phonons are included diagrammatically within the Migdal approximation by also including self-consistency from the electronic feedback. The nonequilibrium steady state is addressed by means of the dynamical mean-field theory based on the nonequilibrium Green's function approach, while the so-called auxiliary master equation approach is employed as impurity solver. With optical phonons the self-consistency suppresses the steady-state current for field strengths comparable to the band gap with respect to the non-self-consistent case. This is due to the interaction of phonons with the hot electrons of the lattice which increases their temperature, thus providing a less effective relaxation channel for the current-induced Joule heat. In addition, in the case of optical phonons, the results are essentially independent of the temperature of the fermionic baths, as the latter is sensibly smaller than their characteristic frequency. On the other hand, with acoustic phonons the steady-state current is slightly suppressed by the self-consistent treatment only at field strengths close to half of the gap and especially at very small phonon frequency. Also, in this case, the results seem to slightly depend on the temperature of the fermionic baths.

We introduce a general concept and consider a characteristic approach to obtain the narrow-band suppression of total electromagnetic scattering independent of the irradiation conditions for the compound dielectric structures supporting unique anapole states. To emphasize this independence from the irradiation conditions, we call the selective superinvisibility effect. We show that the realization of this concept allows us to reach simultaneously several goals significantly suppress the scattering (at a certain wavelength); provide the scattering suppression for any polarization and direction of incidence waves; accumulate electromagnetic energy in the near-field zone and inside of the scatterer. The combination of these physical properties in a compound structure makes it possible to consider them as building blocks for two-dimensional or three-dimensional metamaterials with the selective transparent property practically independent of the irradiation conditions. Our study includes theoretical modeling based on a multipole approach and a corresponding experimental verification.

Here we explore the structural, magnetic, and dielectric properties of ${\mathrm{Na}}_5{\mathrm{Co}}_{15.5}{\mathrm{Te}}_6{\mathrm{O}}_{36}$, which reveal development of a short-range magnetic correlation and a dielectric anomaly in the system above Nèel temperature ($T_N$=) of 50 K. Low-temperature neutron powder diffraction (NPD) without any external magnetic field clearly indicates that the canted spin structure is responsible for the antiferromagnetic transition, and this canted spin structure brings several short-range ferromagnetic and antiferromagnetic correlations, and partially occupied Co form short-range magnetic correlation with other Co. Interestingly, a structural change in terms of changes in the lattice parameters and consequent development of dielectric anomaly around similar temperature is also recorded in the system. Additionally, the isothermal remanent magnetization and electron-spin resonance measurements reveal the presence of short-range magnetic correlations which coincide with an anomaly in the dielectric constant vs temperature curve. Further, a sharp jump in the magnetic-field-dependent magnetization clearly indicates the presence of metamagnetic transition, and magnetic-field-dependent NPD confirms that rotations of Co spins with applied magnetic field are responsible for this metamagnetic phase transition. Consequently, a magnetocaloric effect is developed in the system, which is suitable for the application in low-temperature refrigeration.

To understand the microscopic mechanism of the charge order observed in the parent compound of the infinite-layer nickelate superconductors, we consider a minimal three-legged model consisting of a two-legged Hubbard ladder for the Ni $3d_{x^2-y^2}$ electrons and a free conduction electron chain from the rare-earths. With highly accurate density matrix renormalization group calculations, when the chemical potential difference is adjusted to make the Hubbard ladder with $1/3$ hole doping, we find a long-range charge order with period 3 in the ground state of the model, while the spin excitation has a small energy gap. Moreover, the electron pair-pair correlation has a quasi-long-range behavior, indicating an instability of superconductivity even at half-filling. As a comparison, the same method is applied to a pure two-legged Hubbard model with $1/3$ hole doping in which the period-3 charge order is a quasi-long-range one. The difference between them demonstrates that the free electron chain of the three-legged ladder plays the role of a charge reservoir and enhances the charge order in the undoped infinite-layer nickelates.

We consider a two-dimensional quantum spin system described by a Heisenberg model that is embedded in a three-dimensional metal. The two systems couple via an antiferromagnetic Kondo interaction. In such a setup, the ground state generically remains metallic down to the lowest temperatures and allows us to study magnetic quantum phase transitions in metallic environments. From the symmetry point of view, translation symmetry is present in two out of three lattice directions such that crystal momentum is only partially conserved. Importantly, the construction provides a route to study, with negative-sign-free auxiliary-field quantum Monte Carlo methods, the physics of local moments in metallic environments. Our large-scale numerical simulations show that as a function of the Kondo coupling, the system has two metallic phases. In the limit of strong Kondo coupling, a paramagnetic heavy-fermion phase emerges. Here, the spin degree of freedom is screened by means of the formation of a composite quasiparticle that participates in the Luttinger count. At weak Kondo coupling, magnetic order is present. This phase is characterized by Landau-damped Goldstone modes. Furthermore, the aforementioned composite quasiparticle remains intact across the quantum phase transition.

The electron emission properties of a single-crystal nitrogen-doped diamond(001) photocathode inserted in a 10 kV DC photoelectron gun are determined using a tunable (235–410 nm) ultraviolet laser radiation source for photoemission from both the back nitrogen-doped substrate face and the front homoepitaxially grown and undoped diamond crystal face. The measured spectral trends of the mean transverse energy and quantum efficiency of the emitted electrons are both anomalous and nonmonotonic, but are shown to be consistent with (i) the known physics of electron photoexcitation from the nitrogen substitution states into the conduction bands of diamond, (ii) the energy position and dispersion characteristics of the conduction bands of diamond in the (001) emission direction, (iii) the effective electron affinity of the crystal faces, (iv) the strong electron-(optical)phonon coupling in diamond, and (v) the associated hot electron transport dynamics under energy equipartition with the optical phonons. Notably, the observed hot electron emission is shown to be restricted parallel to the photocathode surface by the low transverse effective masses of the emitting band states—a transverse momentum filtering effect.

We investigate the effects of random onsite disorder on higher-order Thouless pumping of noninteracting fermionic Benalcazar–Bernevig–Hughes (BBH) model. The interplay of disorder-induced topological phase transition and delocalization-localization transition is extensively explored. The higher-order Thouless pumping is characterized by the quantized corner-to-corner charge transport and nonzero Chern number, and the delocalization-localization transition is analyzed by utilizing both inverse participation ratio and finite-size scaling. The results show that the quantized corner-to-corner charge transport is broken for the strong disorder, where the instantaneous bulk energy gap is closed. Although the instantaneous eigenstates are localized for the weak disorder, the charge transport remains quantized. This is attributed to delocalized Floquet states caused by the periodic driving. Furthermore, the phase transition from the quantized charge transport to topologically trivial pumping is accompanied by the disorder-induced delocalization-localization transition of Floquet states.

Nonreciprocal plasmonics plays a crucial role in enabling one-way light propagation at the nanoscale and is a fundamental building block for photonic applications. Here, we investigate intrinsic nonreciprocity in bulk plasmon dispersion in systems that break both parity and time-reversal symmetry. We demonstrate that both interband and intraband bulk plasmon modes exhibit intrinsically asymmetric dispersion depending on the sign of the wave vector. Our study reveals that the intrinsic nonreciprocity in interband plasmon dispersion is governed by quantum metric connection. The nonreciprocity in the intraband plasmon dispersion is dictated by the quantum metric dipole and a higher-order “Drude”-weight-like term. We corroborate our findings via explicit numerical calculations for the two-dimensional Qi-Wu-Zhang model, and we demonstrate the existence of intrinsic nonreciprocal intraband and interband plasmon modes in moiré systems such as twisted bilayer graphene. Our findings offer insights into the underlying physics of nonreciprocal plasmonics and pave the way for designing novel photonic devices.

Spin liquid crystals are magnetic analogs of liquid crystals, possessing properties of both liquids and solids, a typical example of which are spin nematics. Spin nematics share many features with spin liquids, and the interplay between them is a promising, but little explored, route to uncovering new phases of matter. Here, we address this question in the context of a spin-1 magnet on the honeycomb lattice, by considering a model with both biquadratic interactions, favoring spin-nematic states, and Kitaev-like interactions, supporting spin liquids. Accompanying these, where dipole and quadrupole moments compete, we find a plethora of exotic phases, including multiple-$q$ states with nonzero scalar spin chirality, a quasi-one-dimensional coplanar phase, a twisted conical phase, and a noncoplanar order state which gives way to a chiral spin liquid at finite temperature. The implication of these results for experiment is discussed.

Cubic ${\mathrm{BC}}_2\mathrm{N}$, a superhard material with a slightly lower hardness than diamond, has been synthesized but the determination of its crystal structure has long been elusive, impeding the further understanding of pertinent physics. Here, by employing a first-principles electronic structure framework, we predicted a cubic ${\mathrm{BC}}_2\mathrm{N}$ crystal structure (dia-${\mathrm{BC}}_2\mathrm{N}$), marking it as the hitherto cubic phase among all previously proposed structures. Our simulated x-ray diffraction patterns of diamondlike ${\mathrm{BC}}_2\mathrm{N}$ agree with the experimental data, implying that our predicted structure is likely to be the high-symmetry ${\mathrm{BC}}_2\mathrm{N}$ structure synthesized in experiment. Furthermore, the estimated Vicker's hardness of this structure is 77 GPa, demonstrating its intrinsic superhard nature. Our current findings may begin to clarify the long-term unsolved crystal structure of cubic ${\mathrm{BC}}_2\mathrm{N}$, and they may pave the way for further design and discovery of superhard materials.

$A^{\mathrm{V}}{B}^{\mathrm{VI}}{C}^{\mathrm{VII}}$ ($A=\mathrm{Bi}$, Sb; $B=\mathrm{S}$, Se; $C=\mathrm{I}$, Br) semiconductors are promising materials in photoelectric applications and exhibit high tunability of electronic properties. Here, we systematically study the electrical transport, structural, and vibrational properties of photoelectric semiconductor BiSeI at high pressure. With increasing pressure, a small drop in the resistance curve starts to appear at $P_{\mathrm{C}}\sim 27.4$ GPa and zero resistance conductivity is eventually achieved at 40.4 GPa, indicating the occurrence of a superconducting transition. Combined with high-pressure Raman scattering, synchrotron XRD measurements, and theoretical calculations, we demonstrate that this superconductivity originates from a high-pressure phase with space group $P4$/nmm. Upon further compression, $T_C$ initially increases and then changes marginally with a nearly constant 5.6 K above 40.0 GPa, suggesting the robustness of this superconductivity. Our findings will shed light on exploring exotic properties in low-dimensional systems via pressure treatment.

The nuclear and magnetic structure of the spinel $\mathrm{Mn}{\mathrm{Cr}}_2{\mathrm{O}}_4$ is reinvestigated by magnetization, specific heat, and neutron diffraction experiments at different temperatures. Four samples of this spinel synthesized under different atmospheres are analyzed. Through these experiments, a new magnetic phase, with propagation vector ${\vec{k}}_{\mathrm{I}2}=\left(0.6597\left(1\right)0.5999\left(1\right)0.1996\left(2\right)\right)$, not previously reported, is identified below 18 K when the sample is synthesized under a reductive atmosphere. A possible explanation for the different magnetic ground states observed is given based on the competition among the main exchange interactions present in the system. Using the magnetic superspace group formalism, the symmetry of the nuclear and magnetic structures is determined. The presence of transverse conical magnetic structures in the lower-temperature phases allows for multiferroicity in this compound, and the electric polarization direction is determined for each magnetic phase.