The chiral plasmon modes of relativistic matter in background magnetic and strain-induced pseudomagnetic fields are studied in detail using the consistent chiral kinetic theory. The results reveal a number of anomalous features of these chiral magnetic and pseudomagnetic plasmons that could be used to identify them in experiment. In a system with nonzero electric (chiral) chemical potential, the background magnetic (pseudomagnetic) fields not only modify the values of the plasmon frequencies in the long-wavelength limit, but also affect the qualitative dependence on the wave vector. Similar modifications can be also induced by the chiral shift parameter in Weyl materials. Interestingly, even in the absence of the chiral shift and external fields, the chiral chemical potential alone leads to a splitting of plasmon energies at linear order in the wave vector.

Structural and electronic properties of screw and ${60}^{\circ }$-mixed glide and shuffle dislocations in the solar absorber materials ${\mathrm{CuInSe}}_2$ and ${\mathrm{CuGaSe}}_2$ are investigated by means of electronic structure calculations within density functional theory (DFT). Screw dislocations present distorted bonds but remain fully coordinated after structural relaxation. Relaxed ${60}^{\circ }$-mixed dislocations, in contrast, exhibit dangling and “wrong,” cation-cation or anion-anion bonds, which induce deep charge transition levels and are electrically active. Analysis of Bader charges and local density of states (LDOS) reveals that acceptor and donor levels are induced by $\alpha$ and $\beta$ cores, respectively. Moreover, there is local charge accumulation in the surrounding of those cores which contain dangling or “wrong” bonds. Thus the apparently harmless nature of dislocations is not because they are electrically inactive, but can only be a result of passivation by segregating defects.

This report provides a comprehensive understanding of the magnetic quantization effects in phosphorene with the use of the generalized tight-binding model. Especially for bilayer systems, a composite magnetic and electric field can induce the feature-rich LL spectrum. We demonstrate the existence of two subgroups of Landau levels (LLs) near the Fermi level according to their distinguishable localization centers. The strong competition between the two subgroups induces unusual quantization behaviors, such as multiple anticrossings for the $B_z$- and $E_z$-dependent energy spectra. These results are clearly explained by the spatial distributions of subenvelope functions from which two types of LLs are characterized by being either the usual or the perturbed distribution modes. The detailed analysis of the diverse magnetic quantizations is quite important in understanding other physical properties, such as the dispersion relations of magnetoplasmons, magneto-optical selection rules, as well as electron transport properties. The unusual energy spectra are directly revealed by the special features of the density of states, which could be further validated by measurements employing scanning tunneling spectroscopy.

We study the thermodynamic properties of four-component fermionic mixtures described by the Hubbard model using the dynamical mean-field-theory approach. Special attention is given to the system with SU(4)-symmetric interactions at half filling, where we analyze equilibrium many-body phases and their coexistence regions at nonzero temperature for the case of simple cubic lattice geometry. We also determine the evolution of observables in low-temperature phases while lowering the symmetry of the Hamiltonian towards the two-band Hubbard model. This is achieved by varying interflavor interactions or by introducing the spin-flip term (Hund's coupling). By calculating the entropy for different symmetries of the model, we determine the optimal regimes for approaching the studied phases in experiments with ultracold alkali and alkaline-earth-like atoms in optical lattices.

Finite-temperature effects have a pronounced impact on the transport properties of solids. In magnetic systems, besides the scattering of conduction electrons by impurities and phonons, an additional scattering source coming from the magnetic degrees of freedom must be taken into account. A first-principle scheme which treats all these scattering effects on equal footing was recently suggested within the framework of the multiple scattering formalism. Employing the alloy analogy model treated by means of the CPA, thermal lattice vibrations and spin fluctuations are effectively taken into account. In the present work the temperature dependence of the longitudinal resistivity and the anomalous Hall effect in the strongly correlated metal Gd is considered. The comparison with experiments demonstrates that the proposed numerical scheme does provide an adequate description of the electronic transport at finite temperatures.

The paper is motivated by the observation of unusual and not well understood spin dynamics in low- and moderately doped high-$T_c$ cuprates as well as by the discovery in these materials of a static incommensurate order for doping exceeding the insulator-metal boundary in the phase diagram. We develop a microscopic approach that allows us to treat accurately the quantum fluctuations in the spiral state developing upon doping the Mott-Neel insulator. We show that the spiral order of localized spins induces an off-diagonal order of mobile charges and a gap $\mathrm{\Delta }\propto \left|\mathbf{Q}\right|$ in their spectrum $(\mathbf{Q}$ is the spiral incommensurability wave vector defined with respect to ${\mathbf{Q}}_{\mathrm{AF}})$. Due to the dynamic spin-charge interaction the latter gap produces a feedback effect consisting in the appearence of a gap in the coherent spin excitation spectrum. As a result, the characteristic energy ${\omega }_c=\mathrm{\Delta }$ appears, in the spin excitation spectra. It separates two components with qualitatively different behavior–above ${\omega }_c$, spin excitations are magnonlike and have an upward dispersion, below it, they are of the relaxation type and have a slight downward dispersion. The form of the dispersion is close to the form observed experimentally (by inelastic neutron scattering), which can be characterized as OPEN-hour-glass shaped or $Y$-shaped. There is no qualitative difference between the spin dynamics in the normal and SC states as far as doping is relatively low. There is no resonance. Other important features, including the incommensurability and uniaxial anisotropy of the low-energy spin excitations and the doping dependencies of the characteristic energy and wave vectors, are also close to those observed experimentally in low-doped cuprates. We show that the static spiral state becomes unstable at the critical doping $n_c$. We show also that adopting the hypothesis about the presence of finite-energy spiral correlations in the paramagnetic state above $n_c$ and based on the results obtained for the static spiral state, it is possible to understand the spin dynamics observed in the so-called pseudogap state as well as the tendencies of the doping evolution of spin excitations in cuprates from low to high doping.

Adsorption of Au on vicinal Si(111) surfaces results in growth of long-range ordered metallic quantum wires. In this paper, we utilized site-specific and selective adsorption of oxygen to modify chemically the transport via different channels in the systems Si(553)-Au and Si(557)-Au. They were analyzed by electron diffraction and four-tip STM-based transport experiments. Modeling of the adsorption process by density functional theory shows that the adatoms and rest atoms on Si(557)-Au provide energetically favored adsorption sites, which predominantly alter the transport along the wire direction. Since this structural motif is missing on Si(553)-Au, the transport channels remain almost unaffected by oxidation.

The proposal of sliding phases (SP) is revisited from the perspective of duality. A generic argument is formulated as essentially a no-go theorem for SP in translationally invariant nonfrustrated systems with short-range interactions—classical or quantum. Its validity is demonstrated on an asymmetric bilayer and its multilayer variation models where the duality allows obtaining asymptotically exact analytical solution. This solution is in drastic contrast with the perturbative renormalization group prediction and is strongly supported by Monte Carlo simulations. An alternative path toward finding SP is suggested. Its key ingredient is a long-range gauge-type interaction suppressing the interlayer Josephson coupling.

We report the transverse relaxation rates $1/T_2$'s of the ${}^{63}\mathrm{Cu}$ nuclear spin-echo envelope for double-layer high-$T_{\mathrm{c}}$ cuprate superconductors ${\mathrm{HgBa}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_{6+\delta }$ from underdoped to overdoped. The relaxation rate $1/T_{2\mathrm{L}}$ of the exponential function (Lorentzian component) shows a peak at $220–240$ K in the underdoped ($T_{\mathrm{c}}=103$ K) and the optimally doped ($T_{\mathrm{c}}=127$ K) samples but no peak in the overdoped ($T_{\mathrm{c}}=93$ K) sample. The enhancement in $1/T_{2\mathrm{L}}$ suggests a development of the zero frequency components of local field fluctuations. Ultraslow fluctuations are hidden in the pseudogap states.

Fathoming interplay between symmetry and topology of many-electron wave functions has deepened our understanding of quantum many-body systems, particularly after the discovery of topological insulators. Topology of electron wave functions often enforces and protects emergent gapless excitation, and symmetry is intrinsically tied to the topological protection of the excitations. Namely, unless the symmetry is broken, the topological nature of the excitations is intact. We show intriguing phenomena of interplay between symmetry and topology in three-dimensional topological phase transitions associated with line-nodal superconductors. More specifically, we discover an exotic universality class out of topological line-nodal superconductors. The order parameter of broken symmetries is strongly correlated with underlying line-nodal fermions, and this gives rise to a large anomalous dimension in sharp contrast to that of the Landau-Ginzburg theory. Remarkably, hyperscaling violation and emergent relativistic scaling appear in spite of the presence of nonrelativistic fermionic excitation. We also propose characteristic experimental signatures around the phase transitions, for example, a linear phase boundary in a temperature-tuning parameter phase diagram, and discuss the implication of recent experiments in pnictides and heavy-fermion systems.

On the triangular and kagome lattices, short-ranged resonating valence-bond wave functions can be sampled without the sign problem using a recently developed Pfaffian Monte Carlo scheme. In this Rapid Communication, we study the Renyi entanglement entropy in these wave functions using a replica-trick method. Using various spatial bipartitions, including the Levin-Wen construction, our finite-size scaled Renyi entropy gives a topological contribution consistent with $\gamma =ln\left(2\right)$, as expected for a gapped ${\mathbb{Z}}_2$ quantum spin liquid. We prove that the mutual statistics is consistent with the toric code anyon model and rule out any other quasiparticle statistics such as the double semion model.

The pseudogap of the recently discovered Au-Al-Gd quasicrystal approximant crystal (AC) is investigated over a wide electron-per-atom $(e/a)$ ratio of $\sim 0.5$ using thermoelectric properties as an experimental probe. This Au-Al-Gd AC provides an ideal platform for fine probing of the pseudogap among a number of known ACs because the Au-Al-Gd AC possesses an extraordinarily wide single-phase region with respect to the variation in the electron concentration [A. Ishikawa, T. Hiroto, K. Tokiwa, T. Fujii, and R. Tamura, Phys. Rev. B 93, 024416 (2016)], in striking contrast to, for instance, binary stoichiometric $\mathrm{C}{\mathrm{d}}_6\mathrm{R}$ ACs. As a result, a salient peak structure is observed in the Seebeck coefficient, $S$, with the composition as well as that of the power factor $S^2\sigma$, in addition to a gradual variation in the conductivity, $\sigma$, and $S$. These two features are directly associated with rapid and slow variations, respectively, of spectral conductivity $\sigma \left(E\right)$, and hence the fine structure inside the pseudogap, in the vicinity of the Fermi level $E_{\mathrm{F}}$. Based on the observed continuous variation of the Fermi wave vector reported in the previous experimental work, fine tuning of $E_{\mathrm{F}}$ toward an optimal position was attempted, which led to the successful observation of a sharp peak in $S^2\sigma$ with a value of $\sim 270\mu \mathrm{W}/\mathrm{m}·{\mathrm{K}}^2$ at 873 K. This is the highest value ever reported among both Tsai-type and Bergman-type compounds. The dimensionless figure of merit was determined as 0.026 at 873 K, which is also the highest reported among both Tsai-type and Bergman-type compounds.

The cooperative behavior of quantum impurities on two-dimensional (2D) materials, such as graphene and bilayer graphene, is characterized by a nontrivial competition between screening (Kondo effect) and Ruderman-Kittel-Kasuya-Yosida (RKKY) magnetism. In addition, due to the small density of states at the Fermi level, impurities may not couple to the conduction electrons at all, behaving as free moments. Employing a recently developed exact numerical method to study multi-impurity lattice systems, we obtain nonperturbative results that dramatically depart from expectations based on the conventional RKKY theory. At half filling and for weak coupling, impurities remain in the local moment regime when they are on opposite sublattices, up to a critical value of the interactions when they start coupling antiferromagnetically with correlations that decay very slowly with interimpurity distance. At finite doping, away from half filling, ferromagnetism is completely absent and the physics is dominated by a competition between antiferromagnetism and Kondo effect. In bilayer graphene, impurities on opposite layers behave as free moments, unless the interaction is of the order of the hopping or larger.

We investigated current driven spin-orbit torques in $\mathrm{C}{\mathrm{u}}_{40}\mathrm{A}{\mathrm{u}}_{60}/\mathrm{N}{\mathrm{i}}_{80}\mathrm{F}{\mathrm{e}}_{20}/\mathrm{Ti}$ layered structures with in-plane magnetization. We have demonstrated a reliable and convenient method to separate dampinglike torque and fieldlike torque by using the second harmonic technique. It is found that the dampinglike torque and fieldlike torque depend on temperature very differently. Dampinglike torque increases with temperature, while fieldlike torque decreases with temperature, which are different from results obtained previously in other material systems. We observed a nearly linear dependence between the spin Hall angle and longitudinal resistivity, suggesting that skew scattering may be the dominant mechanism of spin-orbit torques.

We have investigated the superconducting (SC) gap on hole Fermi surfaces (FSs) of optimally substituted $\mathrm{Ba}(\mathrm{F}{\mathrm{e}}_{0.65}\mathrm{R}{\mathrm{u}}_{0.35}{)}_2\mathrm{A}{\mathrm{s}}_2$ by angle-resolved photoemission spectroscopy (APRES) using bulk-sensitive 7 eV laser and synchrotron radiation. It was found that, whereas the gap is isotropic in the $k_x-k_y$ plane, the gap magnitudes of two resolved hole FSs show similar $k_z$ dependences and decrease as $k_z$ approaches $\sim 2\pi /c$ (i.e., around the $Z$ point), unlike the other Fe-based superconductors reported so far, where the SC gap of only one hole FS shows a strong $k_z$ dependence. This unique gap structure can be understood in the scenario that the $d_{z^2}$ orbital character is mixed into both hole FSs due to finite spin-orbit coupling (SOC) and is reproduced by calculation within the random phase approximation including the SOC.

We studied thermal and dynamic history effects in the vortex lattice (VL) near the order-disorder transition in clean ${\mathrm{NbSe}}_2$ single crystals. Comparing the evolution of the effective vortex pinning and the bulk VL structure, we observed metastable superheated and supercooled VL configurations that coexist with a hysteretic effective pinning response due to thermal cycling of the system. A novel scenario, governed by the interplay between (lower) elastic and (higher) plastic energy barriers, is proposed as an explanation for our observations: Plastic barriers, which prevent the annihilation or creation of topological defects, require dynamic assistance to be overcome and to achieve a stable VL at each temperature. Conversely, thermal hysteresis in the pining response is ascribed to low energy barriers, which inhibit rearrangement within a single VL correlation volume and are easily overcome as the relative strength of competing interactions changes with temperature.

We disentangle all the individual degrees of freedom in the quantum impurity problem to deconstruct the Kondo singlet, both in real and energy space, by studying the contribution of each individual free electron eigenstate. This is a problem of two spins coupled to a bath, where the bath is formed by the remaining conduction electrons. Being a mixed state, we resort to the “concurrence” to quantify entanglement. We identify “projected natural orbitals” that allow us to individualize a single-particle electronic wave function that is responsible of more than $90\%$ of the impurity screening. In the weak coupling regime, the impurity is entangled to an electron at the Fermi level, while in the strong coupling regime, the impurity counterintuitively entangles mostly with the high energy electrons and disentangles completely from the low-energy states carving a “hole” around the Fermi level. This enables one to use concurrence as a pseudo order parameter to compute the characteristic “size” of the Kondo cloud, beyond which electrons are weakly correlated to the impurity and are dominated by the physics of the boundary.

Diagrammatic extensions of dynamical mean-field theory (DMFT) such as the dynamical vertex approximation $\left(\text{D}\mathrm{\Gamma }\text{A}\right)$ allow us to include nonlocal correlations beyond DMFT on all length scales and proved their worth for model calculations. Here, we develop and implement an Ab initio $\text{D}\mathrm{\Gamma }\text{A}$ approach (Abinitio$\text{D}\mathrm{\Gamma }\text{A}$) for electronic structure calculations of materials. The starting point is the two-particle irreducible vertex in the two particle-hole channels which is approximated by the bare nonlocal Coulomb interaction and all local vertex corrections. From this, we calculate the full nonlocal vertex and the nonlocal self-energy through the Bethe-Salpeter equation. The Abinitio$\text{D}\mathrm{\Gamma }\text{A}$ approach naturally generates all local DMFT correlations and all nonlocal $GW$ contributions, but also further nonlocal correlations beyond: mixed terms of the former two and nonlocal spin fluctuations. We apply this new methodology to the prototypical correlated metal ${\text{SrVO}}_3$.