The chaotic dynamics describes how a small change of initial conditions can result in a large difference in a deterministic nonlinear system, i.e., the “butterfly effect.” Through a combination of experimental and theoretical analysis, here we showed unambiguously that the deformation of metallic glasses (MGs) exhibits such an effect where the experimentally observed plasticity displays a large plasticity fluctuation under the normally same conditions. The “butterfly effect” for the plasticity of MGs is related to the chaotic dynamics of a shear band, evidenced by the existence of a torus destroyed phase diagram, a positive Lyapunov exponent, and a fractional Lyapunov dimension. Physically, the chaotic shear-band dynamics arises from the interplay between structural disordering and temperature rise within the shear band, which could lead to an uncertainty in the appearance of the critical condition for runaway shear banding events. Our results provide a perspective on the plasticity of MGs from the viewpoint of complex dynamics and are also important for evaluating the plastic deformation properties of MGs in practical applications.

We investigate thermodynamic properties of FeSe under in-plane magnetic fields using torque magnetometry, specific heat, and magnetocaloric measurements. Below the upper critical field $H_{c2}$, we observed the field induced anomalies at $H_1\sim 15$ T and $H_2\sim 22$ T near $H\parallel ab$ and below a characteristic temperature $T^{*}\sim$ 2 K. The transition magnetic fields $H_1$ and $H_2$ exhibit negligible dependence on both temperature and field orientation. This contrasts to the strong temperature and angle dependence of $H_{c2}$, suggesting that these anomalies are attributed to the field induced phase transitions, originating from the inherent spin-density-wave instability of quasipaticles near the superconducting gap minima or possible Flude-Ferrell-Larkin-Ovchinnikov state in the highly spin-polarized Fermi surfaces. Our observations imply that FeSe, an atypical multiband superconductor with extremely small Fermi energies, represents a unique model system for stabilizing unusual superconducting orders beyond the Pauli limit.

The noncentrosymmetric superconductor $\alpha$-PdBi is a candidate material for the realization of topological superconductivity. Here, we present a detailed de Haas–van Alphen (dHvA) study together with band-structure calculations within the framework of density functional theory. The rich dHvA spectra are a manifestation of the 13 bands that cross the Fermi energy $E_F$. We find excellent agreement between calculated and experimentally observed dHvA frequencies with moderately enhanced effective masses. One of the bands crossing $E_F$, the so-called $\alpha$ band, exhibits topological character with Weyl nodes lying 43 meV below $E_F$.

We investigate the influence of a static, uncorrelated distribution of charged impurities on the spectrum of bound excitons in the copper oxide ${\mathrm{Cu}}_2\mathrm{O}$. We show that the statistical distribution of Stark shifts and ionization rates leads to the vanishing of Rydberg resonances into an apparent continuum. The appearance of additional absorption lines due to the broken rotational symmetry, together with spatially inhomogeneous Stark shifts, leads to a modification of the observed line shapes that agrees qualitatively with the changes observed in the experiment.

We report first-principles calculations of electron-phonon coupling in bilayer graphene and the corresponding contribution to carrier scattering. At the phonon $\mathrm{\Gamma }$ point, electrons with energies less than 200 meV are scattered predominantly by ${\mathrm{LA}}^{\prime }$ and ${\mathrm{TA}}^{\prime }$ modes while higher-energy electron scattering is dominated by optical phonon modes. Based on a two-temperature model, heat transfer from electrons with an initial temperature of 2000 K to the lattice (phonons) with an initial temperature of 300 K is computed, and in the overall relaxation process, most of this energy scatters into $K$-point phonon optical modes due to their strong coupling with electrons and their high energies. A Drude model is used to calculate photoconductivity for bilayer graphene with different doping levels. Good agreement with prior experimental trends for both the real and imaginary components of photoconductivity confirms the model's applicability. The effects of doping levels and electron-phonon scattering on photoconductivity are analyzed. We also extract acoustic and optical deformation potentials from average scattering rates obtained from density functional theory (DFT) calculations and compare associated photoconductivity calculations with DFT results. The comparison indicates that momentum-dependent electron-phonon scattering potentials are required to provide accurate predictions.

Finite-temperature density functional theory has become a standard tool for first-principles calculations of the properties of warm dense matter (WDM) relevant to high-energy-density physics (HEDP) applications. Here we present theoretical grounds of thermal hybrid exchange-correlation (XC) functionals within the generalized Mermin-Kohn-Sham scheme for an improved description of WDM. Building on the previously developed KSDT (Karasiev-Sjostrom-Dufty-Trickey) [Karasiev et al., Phys. Rev. Lett. 112, 076403 (2014)] local density approximation (LDA) and the KDT16 (Karasiev-Dufty-Trickey 2016) [Karasiev et al., Phys. Rev. Lett. 120, 076401 (2018)] generalized-gradient approximation (GGA) XC free-energy density functionals, we construct a novel thermal hybrid XC functional, referred to here as KDT0. The KDT0 model at low temperature reduces to the popular ground-state PBE0 hybrid due to properties of the used KDT16 density functional approximation. Application to static calculations of electronic band gap and band structure at a wide range of temperatures for various systems of interest to HEDP show that KDT0 provides a significant improvement to the lower LDA and GGA rung XC functionals and to the ground-state PBE0 hybrid.

Multilayers composed of aluminum (Al) and platinum (Pt) exhibit a nonmonotonic trend in thermal resistance with bilayer thickness as measured by time domain thermoreflectance. The thermal resistance initially increases with reduced bilayer thickness only to reach a maximum and then decrease with further shrinking of the multilayer period. These observations are attributed to the evolving impact of an intermixed amorphous complexion approximately 10 nm in thickness, which forms at each boundary between Al- and Pt-rich layers. Scanning transmission electron microscopy combined with energy dispersive x-ray spectroscopy find that the elemental composition of the complexion varies based on bilayer periodicity as does the fraction of the multilayer composed of this interlayer. These variations in complexion mitigate boundary scattering within the multilayers as shown by electronic transport calculations employing density-functional theory and nonequilibrium Green's functions on amorphous structures obtained via finite temperature molecular dynamics. The lessening of boundary scattering reduces the total resistance to thermal transport leading to the observed nonmonotonic trend thereby highlighting the central role of complexion on thermal transport within reactive metal multilayers.

The active harnessing of quantum resources in engineered quantum devices poses unprecedented requirements on device control. Besides the residual interaction with the environment, causing environment-induced decoherence, uncontrolled parameters in the system itself—disorder—remain as a substantial factor limiting the precision and thus the performance of devices. These perturbations may arise, for instance, due to imperfect sample production, stray fields, or finite accuracy of control electronics. Disorder-dressed quantum evolution means a unifying framework, based on quantum master equations, to analyze how these detrimental influences cause deviations from the desired system dynamics. This description may thus contribute to unveiling and mitigating disorder effects towards robust schemes. To demonstrate the broad scope of this framework, we evaluate two distinct scenarios: a central spin immersed in an isotropic spin bath and a random mass Dirac particle. In the former scenario, we demonstrate how the disorder average reflects purity oscillations, indicating the time- and state-dependent severity of the disorder impact. In the latter scenario, we discuss disorder-induced backscattering and disorder-induced Zitterbewegung as consequences of the breakup of spin-momentum locking.

We use series expansion methods to investigate the phase diagram of a spin-1/2 Heisenberg antiferromagnet on the triangular lattice with first- and second-neighbor interactions. We find regions of ${120}^{\circ }$ and collinear “stripe” order, separated by an intermediate nonmagnetic phase, in agreement with results obtained previously using other methods. Magnon excitation spectra in the ordered phases are also obtained, and discussed.

Based on first-principles calculations, we investigated how the intrinsic anomalous Hall conductivity (IAHC) can be tailored in ${\mathrm{Mn}}_3\mathrm{GaN}$ with a noncollinear magnetic ground state. It is observed that IAHC displays a strong dependence with respect to the in-plane magnetization direction between the ${\mathrm{\Gamma }}_{5g}$ and ${\mathrm{\Gamma }}_{4g}$ magnetic configurations, and it is also susceptible to the biaxial strains, where symmetry plays an essential role. Particularly, we demonstrated that significant enhancement of IAHC can be achieved by tuning the relative positions of Weyl nodes with respect to the Fermi energy, resulting in large anomalous Nernst effect.

We thoroughly study the zero temperature properties of monoaxial chiral spin systems under a tilted magnetic field. The magnetic phase diagram includes two kinds of continuous phase transitions and one discontinuous phase transition. We clarify the properties of the phase transition in terms of the helical wave picture and the particle (soliton) picture and also in terms of the interaction between solitons. The interacting-soliton picture properly describes most of the discontinuous phase transition. In addition, we investigate several instabilities of the modulated structures such as an isolated soliton and the surface modulation, since their instabilities should be important to the changes of the magnetic properties. For this purpose, we perform the analyses based on the energy landscape as well as the excitation spectrum; the former approach gives an intuitive interpretation. We clarify the mechanisms of the instabilities through these analyses and draw the stability lines of solitons in the magnetic phase diagram.

We perform a numerical simulation of a three-band Hubbard model with two ${\mathrm{CuO}}_2$ planes and a single CuO chain layer for YBCO cuprates. The spin-fluctuation mediated pairing interaction is computed within the multiband random-phase approximation, and its pairing eigenvalues and eigenfunctions are solved as a function of chain state filling factor $n_c$. We find that for the intrinsic value of $n_c$ in YBCO samples, one obtains the usual $d$-wave pairing symmetry. However, if we dope the chain layers with holes, while keeping the plane states doping fixed, the leading pairing symmetry solution becomes an unconventional $f$-wave symmetry. The mechanism behind the $f$-wave pairing is the competition between the plane states antiferromagnetic nesting and chain states' uniaxial nesting. We also find that the pairing strength is strongly augmented when the flat band bottom of the chain state passes the Fermi level for a fixed plane states doping. The $f$-wave pairing symmetry can be realized in YBCO cuprates in future experiments where the self-doping mechanism between the chain and plane states can be minimized so that only chain state can be selectively hole doped.

In a typical experiment in magnonics, thin films are magnetized in plane and spin waves only carry angular momentum along their spatial propagation direction. Motivated by the experiments of Bozhko et al. [Phys. Rev. Research 2, 023324 (2020)], we show theoretically that for obliquely magnetized thin films, exchange-dipolar spin waves are accompanied by a transverse spin current. We propose an experiment to electrically detect this transverse spin current with Pt strips on top of an yttrium iron garnet film, by comparing the induced spin current for spin waves with opposite momenta. We predict the relative difference to be of the order ${10}^{-4}$, for magnetic fields tilted at least ${30}^{\circ }$ out of plane. This transverse spin current is the result of the long-range dipole-dipole interaction and the inversion symmetry breaking of the interface.

The presence or absence of certain symmetries in the normal state (NS) also determines the symmetry of the Cooper pairs. Here, we show that parity ($\mathcal{P}$-) and time-reversal ($\mathcal{T}$-) odd Dirac insulators (trivial or topological) or metals, sustain a local or intraunit cell pairing that supports corner (in $d=2$) or hinge (in $d=3$) modes of Majorana fermions and stands as a higher-order topological superconductor (HOTSC), when the NS additionally breaks discrete fourfold ($C_4$) symmetry. Although these outcomes do not rely on the existence of a Fermi surface, around it (when the system is doped) the HOTSC takes the form of a mixed parity, $\mathcal{T}$-odd (due to the lack of $\mathcal{P}$ and $\mathcal{T}$ in the NS, respectively) $p+id$ pairing, where the $p(d$)-wave component stems from the Dirac nature of quasiparticles (lack of $C_4$ symmetry) in the NS. Thus, when strained, magnetically ordered Dirac materials, such as doped magnetic topological insulators (${\mathrm{MnBi}}_2{\mathrm{Te}}_4$), can harbor HOTSCs, while the absence of an external strain should be conducive for the axionic $p+is$ pairing.

Available experimental data about static and dynamic critical behaviors of ${\text{Sn}}_2{\text{P}}_2{\text{S}}_6$-type ferroelectrics and $({\mathrm{Pb}}_y{\mathrm{Sn}}_{1-y}{)}_2{\mathrm{P}}_2{\left({\mathrm{Se}}_x{\mathrm{S}}_{1-x}\right)}_6$ mixed crystals with a line of tricritical points and a line of Lifshitz points on the $T-x-y$ phase diagram, which meet at the tricritical Lifshitz point, are described in a combined Blume-Capel anisotropic next-nearest-neighbor Ising model. Such spin-1 Ising models with anisotropic competing first- and second-neighbor interactions is applied for the considered ferroelectrics with mixed displacive versus order/disorder character of phase transitions within the framework of a microscopic model with three-well total energy surface for ferroelectric distortion that was earlier built in an ab initio effective Hamiltonian approach. It was found that below the temperature of the tricritical Lifshitz point, the “chaotic” state accompanied by the coexistence of ferroelectric, metastable paraelectric, and modulated phases is expected. In addition to the frustration of polar fluctuations near the Brillouin zone center, in ${\mathrm{Sn}}_2{\mathrm{P}}_2{\mathrm{S}}_6$ crystals the antipolar fluctuations also strongly develop in the paraelectric phase on cooling to the continuous phase-transition temperature $T_0$. Here, the critical behavior can be described as a crossover between Ising and XY universality classes, which is expected near bicritical points with coupled polar and antipolar order parameters and competing instabilities in $q$ space.

We study the one-dimensional nearest-neighbor tight-binding model of electrons with independently distributed random hopping and no on-site potential (i.e., off-diagonal disorder with particle-hole symmetry, leading to sublattice symmetry, for each realization). For nonsingular distributions of the hopping, it is known that the model exhibits a universal, singular behavior of the density of states $\rho \left(E\right)\sim 1/|E{ln}^3\left|E\right||$ and of the localization length $\xi \left(E\right)\sim |ln|E\left|\right|$, near the band center $E=0$. (This singular behavior is also applicable to random XY and Heisenberg spin chains; it was first obtained by Dyson for a specific random harmonic oscillator chain.) Simultaneously, the state at $E=0$ shows a universal, subexponential decay at large distances $\sim exp[-\sqrt{r/r_0}]$. In this study, we consider singular, but normalizable, distributions of hopping, whose behavior at small $t$ is of the form $\sim 1/\left[t{ln}^{\lambda +1}(1/t)\right]$, characterized by a single, continuously tunable parameter $\lambda >0$. We find, using a combination of analytic and numerical methods, that while the universal result applies for $\lambda >2$, it no longer holds in the interval $0<\lambda <2$. In particular, we find that the form of the density of states singularity is enhanced (relative to the Dyson result) in a continuous manner depending on the nonuniversal parameter $\lambda$; simultaneously, the localization length shows a less divergent form at low energies and ceases to diverge below $\lambda =1$. For $\lambda <2$, the fall-off of the $E=0$ state at large distances also deviates from the universal result and is of the form $\sim exp[-{(r/r_0)}^{1/\lambda }]$, which decays faster than an exponential for $\lambda <1$.

Kondo metal $\mathrm{CePtA}{\mathrm{l}}_4\mathrm{G}{\mathrm{e}}_2$ exhibits long-range antiferromagnetic order below 2.3 K. Neutron powder-diffraction experiments reveal that Ce moments order antiferromagnetically with an incommensurate ordering wave vector $\mathit{k}=\left(1.39,0,0.09\right)$. Inelastic neutron powder scattering experiments show a magnetic excitation at 14.5 meV, which corresponds to the first excited state due to the crystalline electric field splitting of the ground-state multiplet of $\mathrm{C}{\mathrm{e}}^{3+}$. The temperature and field dependence of the magnetization of $\mathrm{CePtA}{\mathrm{l}}_4\mathrm{G}{\mathrm{e}}_2$ is consistent with a doublet ground state with a dominant $|j_{\mathrm{z}}=1/2\rangle$ character and a first excited doublet $|j_{\mathrm{z}}=3/2\rangle$ at 14.5 meV.

Magnetic ordering breaks the time-reversal symmetry, greatly impacting material topological properties. We report the investigation of the magnetic properties of the layered $\mathrm{EuMnS}{\mathrm{b}}_2$, which has two sets of magnetic sublattices. Both the magnetization and electrical resistivity reveal two phase transitions with one at $T_{\mathrm{N},\mathrm{Eu}}\sim 21\mathrm{K}$ and the other at $T_{\mathrm{N},\mathrm{Mn}}\sim 346\mathrm{K}$. Single crystal neutron diffraction refinement indicates that both transitions are originated from magnetic ordering. Below $T_{\mathrm{N},\mathrm{Mn}},$ the Mn sublattice forms the C-type antiferromagnetic (AFM) structure with moments [$(4.5\pm 0.6){\mu }_B$ at 7 K] pointing along the $a$ axis. Below $T_{\mathrm{N},\mathrm{Eu}}$, the Eu sublattice forms the canted A-type AFM structure with moments [$(5.9\pm 0.8){\mu }_{\mathrm{B}}$ at 7 K] lying in the $ac$ plane but pointing (41 ± 1)° away from the $a$ axis. Quantitative analysis indicates that the spin-spin correlation length, while anisotropic, has long-range characteristic in all directions for both the Eu and Mn sublattices.