It is shown that the sign of the product of three Zeeman splitting factors corresponding to the main magnetic axes defines the sign of the Berry phase of a (pseudo) spin in an applied magneic field. Ab initio calculations show that $g_X{g}_Y{g}_Z<0$ is often the case for lanthanide and transition metal complexes, while we prove that it is never achieved in $S$ complexes with dominant second-order magnetic anisotropy. In the case of polynuclear compounds, it is argued that the signs of individual $g_i$, $i=X$, $Y$, $Z$, on each metal site can be extracted from experiment.

We report high-magnetic-field (up to 45 T) $\widehat{c}$-axis thermal-expansion and magnetostriction experiments on ${\mathrm{URu}}_2{\mathrm{Si}}_2$ single crystals. The sample length change $\Delta L_c(T_{\mathrm{HO}})/L_c$ associated with the transition to the “hidden order” phase becomes increasingly discontinuous as the magnetic field is raised above 25 T. The reentrant ordered phase III is clearly observed in both the thermal expansion $\Delta L_c(T)/L_c$ and magnetostriction $\Delta L_c(B)/L_c$ above 36 T, in good agreement with previous results. The sample length is also discontinuous at the boundaries of this phase, mainly at the upper boundary. A change in the sign of the coefficient of thermal expansion ${\alpha }_c=\frac{1}{L_c}(\frac{\partial \Delta L_c}{\partial T})$ is observed at the metamagnetic transition ($B_M\sim 38\mathrm{T}$), which is likely related to the existence of a quantum critical end point.

We propose and formulate an interaction induced staggered spin-orbit order as a new emergent phase of two-dimensional Fermi gases. We show that when some form of inherent spin splitting via Rashba-type spin-orbit coupling renders two helical Fermi surfaces to become significantly “nested,” a Fermi surface instability arises. To lift this degeneracy, a spontaneous symmetry-breaking spin-orbit density wave develops, causing a surprisingly large quasiparticle gapping with chiral electronic states. Since the staggered spin-orbit order is associated with a condensation energy, quantified by the gap value, destroying such spin-orbit interaction costs sufficiently large perturbation field or temperature or dephasing time. The ${\mathrm{BiAg}}_2$ surface state is shown to be a representative system for realizing such novel spin-orbit interaction with tunable and large strength, and the spin splitting is decoupled from charge excitations. These functional properties are relevant for spin electronics, spin caloritronics, and spin-Hall effect applications.

Localization of the helical edge states in quantum spin Hall insulators requires breaking time-reversal invariance. In experiments, this is naturally implemented by applying a weak magnetic field $B$. We propose a model based on scattering theory that describes the localization of helical edge states due to coupling to random magnetic fluxes. We find that the localization length is proportional to $B^{-2}$ when $B$ is small and saturates to a constant when $B$ is sufficiently large. We estimate especially the localization length for the HgTe/CdTe quantum wells with known experimental parameters.

Scanning tunnelling microscopy and spectroscopy experiments complemented by first-principles calculations have been conducted to study the electronic structure of 4 monolayer Bi(110) nanoribbons on epitaxial graphene on silicon carbide [$4H\mathrm{\text{−}}\mathrm{SiC}(0001)$]. In contrast with the semimetal property of elemental bismuth, an energy gap of 0.4 eV is measured at the centre of the Bi(110) nanoribbons. Edge reconstructions, which can facilitate the edge strain energy release, are found to be responsible for the band gap opening. The calculated density of states around the Fermi level are decreased quickly to zero from the terrace edge to the middle of a Bi(110) nanoribbon potentially signifying a spatial metal-to-semiconductor transition. This study opens new avenues for room-temperature bismuth nanoribbon-based electronic devices.

We show how the phases of interacting particles in topological flat bands, known as fractional Chern insulators, can be adiabatically connected to incompressible fractional quantum Hall liquids in the lowest Landau level of an externally applied magnetic field. Unlike previous evidence suggesting the similarity of these systems, our approach enables a formal proof of the equality of their topological orders, and furthermore this proof robustly extends to the thermodynamic limit. We achieve this result using the hybrid Wannier orbital basis proposed by Qi [Phys. Rev. Lett. 107, 126803 (2011)] in order to construct interpolation Hamiltonians that provide continuous deformations between the two models. We illustrate the validity of our approach for the ground state of bosons in the half filled Chern band of the Haldane model, showing that it is adiabatically connected to the $\nu =1/2$ Laughlin state of bosons in the continuum fractional quantum Hall problem.

We use the nonequilibrium bosonization technique to investigate the effects of the Coulomb interaction on quantum Hall edge states at a filling factor $\nu =2$, partitioned by a quantum point contact (QPC). We find that, due to the integrability of charge dynamics, edge states evolve to a nonequilibrium stationary state with a number of specific features. In particular, the noise temperature $\Theta$ of a weak backscattering current between edge channels is linear in voltage bias applied at the QPC, independently of the interaction strength. In addition, it is a nonanalytical function of the QPC transparency $T$ and scales as $\Theta \propto T\ln (1/T)$ at $T\ll 1$. Our predictions are confirmed by exact numerical calculations.

We study the unitary relaxation dynamics of disordered spin chains following a sudden quench of the Hamiltonian. We give analytical arguments, corroborated by specific numerical examples, to show that the existence of a stationary state depends crucially on the spectral and localization properties of the final Hamiltonian, and not on the initial state. We test these ideas on integrable one-dimensional models of the Ising or $XY$ class, but argue more generally on their validity for more complex (nonintegrable) models.

Numerical simulations of dynamos in rotating Rayleigh-Bénard convection in plane layers are presented. Two different types of dynamos exist which obey different scaling laws for the amplitude of the magnetic field. The transition between the two occurs within a hydrodynamically uniform regime which can be classified as rapidly rotating convection.

We reveal the nature of the avalanche collapse of the giant viable component in multiplex networks under perturbations such as random damage. Specifically, we identify latent critical clusters associated with the avalanches of random damage. Divergence of their mean size signals the approach to the hybrid phase transition from one side, while there are no critical precursors on the other side. We find that this discontinuous transition occurs in scale-free multiplex networks whenever the mean degree of at least one of the interdependent networks does not diverge.

A three-component Fermi gas near a broad Feshbach resonance does not have a universal ground state due to the Thomas collapse, while it does near a narrow Feshbach resonance. We explore its universal phase diagram in the plane of the inverse scattering length $1/a{k}_F$ and the resonance range $R_{*}{k}_F$. For a large $R_{*}{k}_F$, there exists a Lifshitz transition between superfluids with and without an unpaired Fermi surface as a function of $1/a{k}_F$. With decreasing $R_{*}{k}_F$, the Fermi surface coexisting with the superfluid can change smoothly from that of atoms to trimers (“atom-trimer continuity”), corresponding to the quark-hadron continuity in a dense nuclear matter. Eventually, there appears a finite window in $1/a{k}_F$ where the superfluid is completely depleted by the trimer Fermi gas, which gives rise to a pair of quantum critical points. The boundaries of these three quantum phases are determined in regions where controlled analyses are possible and are also evaluated based on a mean-field plus trimer model.

A localized qubit entangled with a propagating quantum field is well suited to study nonlocal aspects of quantum mechanics and may also provide a channel to communicate between spatially separated nodes in a quantum network. Here, we report the on-demand generation and characterization of Bell-type entangled states between a superconducting qubit and propagating microwave fields composed of zero-, one-, and two-photon Fock states. Using low noise linear amplification and efficient data acquisition we extract all relevant correlations between the qubit and the photon states and demonstrate entanglement with high fidelity.

We demonstrate feedback control of a superconducting transmon qubit using discrete, projective measurement and conditional coherent driving. Feedback realizes a fast and deterministic qubit reset to a target state with 2.4% error averaged over input superposition states, and allows concatenating experiments more than 10 times faster than by passive initialization. This closed-loop qubit control is necessary for measurement-based protocols such as quantum error correction and teleportation.

Quantum walks have by now been realized in a large variety of different physical settings. In some of these, particularly with trapped ions, the walk is implemented in phase space, where the corresponding position states are not orthogonal. We develop a general description of such a quantum walk and show how to map it into a standard one with orthogonal states, thereby making available all the tools developed for the latter. This enables a variety of experiments, which can be implemented with smaller step sizes and more steps. Tuning the nonorthogonality allows for an easy preparation of extended states such as momentum eigenstates, which travel at a well-defined speed with low dispersion. We introduce a method to adjust their velocity by momentum shifts, which allows us to experimentally probe the dispersion relation, providing a benchmarking tool for the quantum walk, and to investigate intriguing effects such as the analog of Bloch oscillations.

We find a realization of linear electroelasticity theory in gravitational physics by uncovering a new response coefficient of charged black branes, exhibiting their piezoelectric behavior. Taking charged dilatonic black strings as an example and using the blackfold approach we measure their elastic and piezolectric moduli. We also use our results to draw predictions about the equilibrium condition of charged dilatonic black rings in dimensions higher than six.

It is shown that extensions to general relativity, which introduce a strongly coupled scalar field, can be viable if the interaction has a nonconformal form. Such disformal coupling depends upon the gradients of the scalar field. Thus, if the field is locally static and smooth, the coupling becomes invisible in the Solar System: this is the disformal screening mechanism. A cosmological model is considered where the disformal coupling triggers the onset of accelerated expansion after a scaling matter era, giving a good fit to a wide range of background observational data. Moreover, the interaction leaves signatures in the formation of large-scale structure that can be used to probe such couplings.

Natural models of supersymmetry with a gravitino lightest supersymmetric particle provide distinctive signatures at the LHC. For a neutralino next-to-lightest supersymmetric particle, sparticles can decay to two high energy photons plus missing energy. We use the ATLAS diphoton search with $4.8{\mathrm{fb}}^{-1}$ of data to place limits in both the top-squark–gluino and neutralino-chargino mass planes for this scenario. If the neutralino is heavier than 50 GeV, the lightest top squark must be heavier than 580 GeV, the gluino must be heavier than 1100 GeV, and charginos must be heavier than approximately 300–470 GeV. This provides the first nontrivial constraints in natural gauge mediation models with a neutralino next-to-lightest supersymmetric particle decaying to photons and implies a fine-tuning of at least a few percent in such models.

We carry out the first complete calculation of kinematic power corrections $\sim t/Q^2$ and $\sim m^2/Q^2$ to the helicity amplitudes of deeply virtual Compton scattering. This result removes an important source of uncertainties in the quantum chromodynamics predictions for intermediate momentum transfers $Q^2\sim 1–10{\mathrm{GeV}}^2$ that are accessible in the existing and planned experiments. In particular, the finite-$t$ corrections are significant and must be taken into account in the data analysis.

Control over various fragmentation reactions of a series of polyatomic molecules (acetylene, ethylene, 1,3-butadiene) by the optical waveform of intense few-cycle laser pulses is demonstrated experimentally. We show both experimentally and theoretically that the responsible mechanism is inelastic ionization from inner-valence molecular orbitals by recolliding electron wave packets, whose recollision energy in few-cycle ionizing laser pulses strongly depends on the optical waveform. Our work demonstrates an efficient and selective way of predetermining fragmentation and isomerization reactions in polyatomic molecules on subfemtosecond time scales.

We perform a joint measurement of terahertz waves and high-harmonics generated from argon atoms driven by a fundamental laser pulse and its second harmonic. By correlating their dependence on the phase delay between the two pulses, we determine the generation of THz waves in tens of attoseconds precision. Compared with simulations and models, we find that the laser-assisted soft collision of the electron wave packet with the atomic core plays a key role. It is demonstrated that the rescattering process, being indispensable in high-harmonic generation processes, dominates THz wave generation as well in a more elaborate way. The new finding might be helpful for the full characterization of the rescattering dynamics.