The study of relaxational behavior of multicomponent metallic liquids still holds the key to understanding and improving the glass-forming abilities of bulk metallic glasses. Herein, we report measurements of the collective relaxation times in a melted bulk metallic glass $\left(\mathrm{LM}601{\mathrm{Zr}}_{51}{\mathrm{Cu}}_{36}{\mathrm{Ni}}_4{\mathrm{Al}}_9\right)$ in the kinetic regime $(Q$: $1.5–4.0{\AA }^{-1})$ using quasielastic neutron scattering. The results reveal an unusual slope change in the Angell plots of the collective relaxation time of this metallic liquid around $950{}^{\circ }\mathrm{C}$, beyond the melting point of the material. Specific heat capacity measurement also reveals the presence of a peak around the same temperature. The coincidence is rationalized using Adams-Gibbs theory, and motivates more careful experimental and computational studies of the metallic liquids in the future.

We report a ${}^7\mathrm{Li}$ nuclear magnetic resonance (NMR) study of a frustrated three-dimensional spin-$\frac{1}{2}$ antiferromagnet ${\text{Li}}_2{\text{CuW}}_2{\text{O}}_8$ and also explore the effect of nonmagnetic dilution. The magnetic long-range ordering in the parent compound at $T_{\mathrm{N}}\simeq 3.9\mathrm{K}$ was detected from the drastic line broadening and a peak in the spin-lattice relaxation rate ($1/T_1$). The NMR spectrum above $T_{\mathrm{N}}$ broadens systematically, and its full width at half maximum (FWHM) tracks the static spin susceptibility. From the analysis of FWHM vs static susceptibility, the coupling between the Li nuclei and ${\text{Cu}}^{2+}$ ions was found to be purely dipolar in nature. The magnitude of the maximum exchange coupling constant is $J_{\max }/k_{\mathrm{B}}\simeq 13\mathrm{K}$. NMR spectra below $T_{\mathrm{N}}$ broaden abruptly and transform into a double-horn pattern reflecting the commensurate nature of the spin structure in the ordered state. Below $T_{\mathrm{N}}$, $1/T_1$ follows a $T^5$ behavior. The frustrated nature of the compound is confirmed by persistent magnetic correlations at high temperatures well above $T_{\mathrm{N}}$. The dilution of the spin lattice with nonmagnetic Zn atoms has dramatic influence on $T_N$ that decreases exponentially similar to quasi-one-dimensional antiferromagnets, even though ${\text{Li}}_2{\text{CuW}}_2{\text{O}}_8$ has only a weak one-dimensional anisotropy. Heat capacity of doped samples follows power law ($C_{\mathrm{p}}\propto T^{\alpha }$) below $T_{\mathrm{N}}$, and the exponent ($\alpha$) decreases from 3 in the parent compound to 1 in the 25% doped sample.

Long-range interactions drive some of the rich phenomenology of quasiparticle collective states in the fractional quantum Hall regime. We test for analogs in models of fractional Chern insulators (FCIs) derived from a screened Coulomb interaction. We find that the uniform FCI liquid is surprisingly robust to long-range interactions but gives way to a unidirectional charge-density wave of fractionally charged quasiparticles with increased screening length. Our results show that FCIs offer a robust and important platform for studying quasiparticle collective states.

We present analysis of a single-channel interacting quantum wire problem in the presence of spin-orbit interaction. The spin-orbit coupling breaks the spin-rotational symmetry from SU(2) to U(1) and breaks inversion symmetry. The low-energy theory is then a two-band model with a difference of Fermi velocities $\delta v$. Using bosonization and a two-loop renormalization group procedure, we show that electron-electron interactions can open a gap in the spin sector of the theory when the interaction strength $U$ is smaller than $\delta v$ in appropriate units. For repulsive interactions, the resulting strong coupling phase is of the spin-density-wave type. We show that this phase has peculiar emergent topological properties. The gapped spin sector behaves as a topological insulator, with zero-energy edge modes with fractional spin. On the other hand, the charge sector remains critical, meaning the entire system is metallic. However, this bulk electron liquid as a whole exhibits properties commonly associated with the one-dimensional edge states of two-dimensional spin Hall insulators, in particular, the conduction of $2e^2/h$ is robust against nonmagnetic impurities.

The naturally weak spin-orbit coupling in graphene can be largely enhanced by adatom deposition [e.g., Weeks et al., Phys. Rev. X 1, 021001 (2011)]. However, the dynamics of the adatoms also induces a coupling between phonons and the electron spin. Using group theory and a tight-binding model, we systematically investigate the coupling between the low-energy in-plane phonons and the electron spin in single-layer graphene uniformly decorated with heavy adatoms. Our results provide the foundation for future investigations of spin transport and superconductivity in this system. In order to quantify the effect of the coupling to the lattice on the electronic spin dynamics, we compute the spin-flip rate of electrons and holes. We show that the latter exhibits a strong dependence on the quasiparticle energy and system temperature.

Electronic and optical properties of graphene depend strongly on many-body interactions. Employing the highly accurate many-body perturbation approach based on Green's functions, we find a large renormalization over independent particle methods of the fundamental band gaps of semiconducting graphene structures with periodic defects. Additionally, their exciton binding energies are larger than 0.4 eV, suggesting significantly strengthened electron-electron and electron-hole interactions. Their absorption spectra show two strong peaks whose positions are sensitive to the defect fraction and distribution. The strong near-edge optical absorption and excellent tunability make these two-dimensional materials promising for optoelectronic applications.

We consider a semiconducting carbon nanotube (CNT) lying on a ferromagnetic insulating substrate with one end passing the substrate and suspended over a metallic gate. We assume that the polarized substrate induces an exchange interaction acting as a local magnetic field for the electrons in the nonsuspended CNT side. Generalizing the approach of I. Snyman and Yu.V. Nazarov [Phys. Rev. Lett. 108, 076805 (2012)], we show that one can generate electrostatically a tunable spin-polarized polaronic state localized at the bending end of the CNT. We argue that at low temperatures manipulation and detection of the localized quantum spin state are possible.

We report on the valley blockade and the multielectron Kondo effect generated by an impurity atom in a silicon nanofield effect device. According to the spin-valley nature of tunneling processes, and consistently with those allowed by the valley blockade regime, the manifestation of Kondo effect at occupation $N=1,2,3$ has the periodicity 4 of the electron filling sequence typical of silicon. The spin-valley Kondo effect emerges under different kinds of screening depending on the electron filling. By exploiting the valley blockade regime, valley index conservation in the Kondo SU(4) is deduced with no need of an external magnetic field. Microwave irradiation suppresses the Kondo effect at occupancies up to three electrons.

Hybridization of atomic orbitals in graphene on $\mathrm{Ni}\left(111\right)$ opens up a large energy gap of $\approx 2.8\mathrm{eV}$ between nonhybridized states at the $K$ point. Here we use alkali-metal adsorbate to reduce and even eliminate this energy gap, and also identify a new mechanism responsible for decoupling graphene from the Ni substrate without intercalation of atomic species underneath. Using angle-resolved photoemission spectroscopy and density functional theory calculations, we show that the energy gap is reduced to 1.3 eV due to moderate decoupling after adsorption of Na on top of graphene. Calculations confirm that after adsorption of Na, graphene bonding to Ni is much weaker due to a reduced overlap of atomic orbitals, which results from $n$ doping of graphene. Finally, we show that the energy gap is eliminated by strong decoupling resulting in a quasifreestanding graphene, which is achieved by subsequent intercalation of the Na underneath graphene. The ability to partially decouple graphene from a Ni substrate via $n$ doping, with or without intercalation, suggests that the graphene-to-substrate interaction could be controlled dynamically.

The nucleation, growth, and propagation of like-spin domains in spin-crossover materials was investigated during the relaxation process of a metastable HS state at low temperature using an electroelastic model running on a deformable two-dimensional square lattice. We distinguish the onset of patterns formation of low-spin domain as the intermolecular interaction is increased, passing successively through random dispersion to clustering pattern and ending up with an impressive single macroscopic domain growth. Attaining and maintaining a single-domain configuration through the transition is attributed to the long-range character of interactions. Qualitative investigation of the elastic energy, of the propagation of the low-spin domain, and of the displacement field are presented. We demonstrate that as the intermolecular interaction increases the propagation of the like-spin domain slowdown. The deformations are believed as the prolonged effect of the intermolecular interactions that are at the origin of the onset of dispersed, poly-, and single-domain nucleation. Spatial autocorrelation of the deformations analysis based on Moran's $I$ index is used. We demonstrate that at short distance significant spatially autocorrelated patterns are detected, and the extent of the autocorrelation decreases with the distance.

The experimental observation of an efficient second-order nonlinearity with dominating frequency upconversion is reported for one-dimensional (1D) guided elastic waves localized at solid edges. These 1D acoustic wedge waves are a fundamental type of elastic wave with a phase velocity below that of surface and bulk waves and no coupling to them. Acoustic pulses, showing steepening, narrowing, and spiking to shocklike profiles, were generated and detected by a laser-based pump-probe setup. Shock formation is described by a nonlinear evolution equation, which allows the characteristic features of 1D guided shock waves to be predicted that differ from their bulk and surface analogs.

Hyperfine interactions and Fe-specific lattice dynamics in ${\mathrm{CuFeO}}_2$ were investigated by nuclear resonance scattering methods and compared to ab initio lattice dynamics calculations. Using nuclear forward scattering the collinear spin structure at temperatures below about 11 K could be confirmed, whereas the nuclear forward scattering results in the intermediate temperature range between about 11 K and 14 K are incompatible with the assumption of a sinusoidal distribution of spins parallel to the $c$ axis of ${\mathrm{CuFeO}}_2$. The critical behavior of the average hyperfine field at the phase transition at about 14 K further supports a three-dimensional model for the magnetism in this compound. Moreover, using nuclear inelastic scattering by the ${}^{57}\mathrm{Fe}$ Mössbauer resonance, Fe-specific lattice dynamics are found to be strongly anisotropic with stiffer bonds in the $ab$ plane of the crystal. The powder averaged, Fe partial density of phonon states can be well modeled using ab initio calculations and low-energy phonons are found to deviate from classical Debye-like behavior, indicating spin-phonon coupling in this compound. Besides, the theoretical phonon spectrum exhibits typical characteristics for delafossite-type material.

Lithium diffusion in spinel ${\mathrm{Li}}_4{\mathrm{Ti}}_5{\mathrm{O}}_{12}$ and ${\mathrm{LiTi}}_2{\mathrm{O}}_4$ compounds for future battery applications has been studied with muon spin relaxation (${\mu }^{+}\mathrm{SR})$. Measurements were performed on both thin-film and powder samples in the temperature range between 25 and 500 K. For ${\mathrm{Li}}_4{\mathrm{Ti}}_5{\mathrm{O}}_{12}$ and above about $\sim 200\mathrm{K}$, the field distribution width ($\mathrm{\Delta })$ is found to decrease gradually, while the field fluctuation rate ($\nu )$ increases exponentially with temperature. For ${\mathrm{LiTi}}_2{\mathrm{O}}_4$, on the contrary, the $\mathrm{\Delta }\left(T\right)$ curve shows a steplike decrease at $\sim 350\mathrm{K}$, around which the $\nu \left(T\right)$ curve exhibits a local maximum. These behaviors suggest that ${\mathrm{Li}}^{+}$ starts to diffuse above around 200 K for both spinels. Assuming a jump diffusion of ${\mathrm{Li}}^{+}$ at the tetrahedral $8a$ site to the vacant octahedral $16c$ site, diffusion coefficients of ${\mathrm{Li}}^{+}$ at 300 K in the film samples are estimated as $(3.2\pm 0.8)\times {10}^{-11} {\mathrm{cm}}^2$/s for ${\mathrm{Li}}_4{\mathrm{Ti}}_5{\mathrm{O}}_{12}$ and $(3.6\pm 1.1)\times {10}^{-11} {\mathrm{cm}}^2$/s for ${\mathrm{LiTi}}_2{\mathrm{O}}_4$. Further, some small differences are found in both thermal activation energies and Li-ion diffusion coefficients between the powder and thin-film samples.

We derive the quasiclassical equations that describe two-dimensional superconductors with a large Rashba spin-orbit coupling and in the presence of impurities. These equations account for the helical phase induced by an in-plane magnetic field, with a superconducting order parameter that is spatially modulated along a direction perpendicular to the field. We also derive the generalized Ginzburg-Landau functional, which includes a linear-in-gradient term corresponding to the helical phase. This theory paves the way for studies of the proximity effect in two-dimensional electron gases with large spin-orbit coupling.

Ab initio electronic structure calculations reveal that epitaxial strain has a dramatic effect on the voltage-controlled magnetic anisotropy (VCMA) in Ta/FeCo/MgO junctions. Strain can give rise to a wide range of novel VCMA behaviors where the MA can change from a $\vee$- to a $\wedge$-shape electric-field dependence with giant VCMA coefficients which are asymmetric under voltage reversal. The underlying mechanism is the interplay of the strain- and electric-field-induced changes in the spin-orbit coupled $d$ states at the interfaces and the strain-induced modification of the dielectric constant of MgO. These findings demonstrate the feasibility of highly sensitive VCMA through strain engineering, which may provide a viable avenue for tailoring magnetoelectric properties for spintronic applications.

Magnonics explores precessional excitations of ordered spins in magnetic materials—so-called spin waves—and their use as information and signal carriers within networks of magnonic waveguides. Here, we demonstrate that the nonuniformity of the internal magnetic field and magnetization inherent to magnetic structures creates a medium of graded refractive index for propagating magnetostatic waves and can be used to steer their propagation. The character of the nonuniformity can be tuned and potentially programmed using the applied magnetic field, which opens exciting prospects for the field of graded-index magnonics.