We demonstrate that, contrary to common wisdom, genuine multipartite entanglement (GME) can be abundantly generated from simple noncorrelated many-electron states. We show that the extracted GME can be maximized via spin-independent transformations derived from the quantum Fourier transform. We further demonstrate the possibility of maximizing the GME through localized orbitals in a variety of realistic systems and correlated states. Towards the exploitation of potentially useful entanglement, we rationalize system-specific and universal features of the extracted GME.

The advent of organic polaritonics has led to the realization of all-optical transistors, logic gates, and single photon switches operating at room temperature. In this Letter, we develop a microscopic theory accounting for thermalization, vibron relaxation, and kinetic bimolecular quenching of polaritons and excitons to investigate the intrinsic limitations of the temporal separation of consecutive polariton condensates. We test and verify our theoretical predictions using an optical pump-pump configuration with different pulse widths and unravel the importance of kinetic losses in defining the upper limit of the temporal bandwidth, reaching $\sim 240\mathrm{GHz}$.

In this paper, we introduce a first-principles-based lattice mode analysis method to investigate the competition between different polarization switching paths in ${\mathrm{HfO}}_2$. Because the stability of the polar orthorhombic $Pca{2}_1$ phase of ${\mathrm{HfO}}_2$ arises from a trilinear coupling, polarization switching requires the flipping of not only the polar ${\mathrm{\Gamma }}_{15}^Z$ mode, but also at least one zone-boundary antipolar mode. This means that each polarization state has multiple variants, leading to multiple possible switching paths connecting up- and down-polarized states, which can be systemically enumerated within this framework for efficient identification of the optimal switching path. Our lattice mode analysis also explains why the activation energy of propagation of the most widely studied domain-wall structure in ${\mathrm{HfO}}_2$, which requires the reversal of the $X_2^{-}$ mode, is much larger than that of propagation of domain-wall structures with a uniform sign for the $X_2^{-}$ mode. This approach deepens our understanding of distinctive properties of ferroelectric ${\mathrm{HfO}}_2$ related to polarization switching and domain-wall motion, including sluggish domain-wall motion, robust ferroelectricity in thin films, and the observation that the antipolar $Pbca$ phase can hardly be transformed to the ferroelectric $Pca{2}_1$ phase by an electric field. Our mode analysis method can be more generally applied to any improper or hybrid improper ferroelectric, in which polarization switching requires changes of nonpolar distortions, for systematic and efficient prediction of optimal switching paths and estimation of coercive fields.

We theoretically and numerically investigate Chern vector insulators and topological surface states in a three-dimensional lattice, based on phase-delayed temporally periodic interactions within the tight-binding model. These Floquet interactions break time-reversal symmetry, effectively inducing a gauge field analogous to magnetic flux. This gauge field results in Chern numbers in all spatial dimensions, collectively forming the Chern vector. This vector characterizes the topological phases and signifies the emergence of robust surface states. Numerically, we observe these states propagating unidirectionally without backscattering on all open surfaces of the three-dimensional system. Our paper paves the way for breaking time-reversal symmetry and realizing three-dimensional Chern vector topological insulators using temporally periodic Floquet techniques.

Understanding how phonon-mediated heat conduction responds to varying strain is critical, yet remains a challenge considering the interplay between particlelike phonons and wavelike mutual coherent phonons. In this study, we conduct comprehensive theoretical investigations into heat transport in ${\mathrm{AgTlI}}_2$ using ab initio calculations and anharmonic lattice dynamics. It is found that, under applied strain ranging from 1% to $-6\%$, the thermal conductivity of ${\mathrm{AgTlI}}_2$ contributed by particlelike phonons exhibits a significant increase from 0.114 W ${\mathrm{m}}^{-1}{\mathrm{K}}^{-1}$ to 0.426 W ${\mathrm{m}}^{-1}{\mathrm{K}}^{-1}$ by 3.7 times. In contrast, the wavelike mutual coherent phonon component exhibits remarkable robustness and changes only 5.82%. The spectral analyses revealed that, for coherent phonon transport, there exit competitive mechanisms of increase for interbranch phonon group velocity and decrease for interbranch phonon lifetime, which is distinct to particlelike phonons. Additionally, it is also found that wavelike mutual coherent phonons have a large contribution to, and can even dominate, thermal transport in ${\mathrm{AgTlI}}_2$. The findings here provide deeper insight and a picture for thermal engineering with two-channel phonon transport under strain.

Motivated by the recent appearance of the trillium lattice in the search for materials hosting spin liquids, we study the ground state of the classical Heisenberg model on its line graph, the trilline lattice. We find that this network realizes the recently proposed notion of a fragile spin liquid in three dimensions. Additionally, we analyze the Ising case and argue for a possible ${\mathbb{Z}}_2$ quantum spin liquid phase in the corresponding quantum dimer model. Like the well-known $U\left(1\right)$ spin liquids, the classical phase hosts moment fractionalization evidenced by the diluted lattice, but unlike those, it exhibits exponential decay in both spin correlations and interactions between fractionalized moments. This provides an instance of a purely short-range correlated classical Heisenberg spin liquid in three dimensions.

Electrons on a kagome lattice exhibit a wealth of features, including Dirac points, van Hove singularities, and flatbands. When the Fermi level is placed at the van Hove saddle point, the Fermi surface is perfectly nested, and a rich variety of electronic instabilities is known to occur. The material realization of such a scenario is a recently discovered kagome system ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$ whose superconductivity near charge-density wave instability at low temperatures points to an unconventional, non-electron-phonon, pairing mechanism. Here we use a recently developed combination of density functional theory with momentum and frequency-resolved self-energies deduced from the so-called fluctuational-exchange-type random phase approximation to study charge fluctuation mediated pairing tendencies in ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$ in the regime where these fluctuations are dynamic and provide the most significant contribution to pairing. Based on our numerical diagonalization of the BCS gap equation, two competing solutions emerge from these calculations with $A_{1g}$ (anisotropic $s$-wave-like) and $E_{2g}$ ($d_{x^2-y^2},d_{xy}$-like) symmetries of the superconducting order parameter. Our evaluated Eliashberg spectral functions ${\alpha }^{2}F\left(\omega \right)$ are purely due to electronic correlations; they were found to be strongly peaked in the vicinity of frequency 7 meV that sets the scale of charge fluctuations. The superconducting coupling constants for the leading pairing channels are estimated as a function of the nearest neighbor Coulomb interaction $V,$ a well-known prime parameter of the extended Hubbard model. They were found in the range of 0.2–0.4 depending on $V$. We evaluate the superconducting $T_c$ close to the values that are observed experimentally that point to the charge fluctuations to provide a substantial contribution to the pairing mechanism in ${\mathrm{CsV}}_3{\mathrm{Sb}}_5.$

The superconducting pairing symmetry is significantly constrained by lattice symmetry, yet how this pairing symmetry evolves with changes in lattice symmetry remains unclear. In this study, through variational quantum Monte Carlo simulations on the Hubbard model, we investigate the evolution of the superconducting ground state on an anisotropic triangular lattice with smoothly tunable frustration. At half-filling, we identify a hidden $C_6$-like $s+d+id$-wave superconductivity, which breaks time-reversal symmetry, emerging for moderate frustrations. This occurs as the lattice symmetry transitions from $C_4$ to $C_2$, where the $d_{x^2-y^2}$-wave and $s+d_{xy}$-wave superconducting ground states dominate, respectively. Notably, we find an isotropic-like $d+id$-wave superconducting phase at $t^{\prime }/t\approx 0.7$, much lower than the expected value $t^{\prime }/t=1$ predicted by most previous studies. At high electron doping levels, we further discover an unexpected quasi-one-dimensional $d_{xy}^{\prime }$-wave superconductivity characterized by strong pairing on the next-nearest-neighbor bond, despite the absence of direct hopping. The numerical data also reveal that pairing symmetries, belonging to distinct irreducible representations of the given point group, can mix together, beyond the conventional theories based on the linear gap equations.

Recently, rotation sensors utilizing the nuclear spins of nitrogen-vacancy color centers in diamond have been demonstrated. However, these devices are power intensive and challenging to integrate into small chip-based radiofrequency antennas and circuits necessary for controlling nuclear spins or producing relatively high magnetic fields. To address this issue, the coherent manipulation of nuclear spins via coherent population trapping at moderate magnetic fields using microwave fields has been successfully demonstrated in isotopically pure diamond. In this work, we demonstrate that a similar technique can be applied to a diamond plate with a natural abundance of carbon-13, which holds significant potential for practical sensing applications. Although the forbidden resonances required for coherent control were only partially observed, coherent population trapping was successfully demonstrated at both visible and invisible transitions, with an apparent contrast of up to 98 ± 11% and a true contrast of approximately 35 ± 7%. This finding confirms the feasibility of coherent nuclear spin control even in diamond plates with naturally occurring carbon-13.

The optical emission spectra of semiconducting transition metal dichalcogenide monolayers highlight fascinating recombination processes of charged excitons (trions). When charge-tunable $\mathrm{WS}{\mathrm{e}}_2$ monolayers are moderately doped with electrons, a strong luminescence peak emerges just below the well-understood spectral lines associated with the recombination of negatively charged bright and dark trions. Despite previous investigations, its origin remains elusive. Here, we demonstrate that this luminescence peak is the result of electron-electron assisted recombination that brightens the dark trion emission. Supporting evidence for this second-order recombination process comes from identifying the brightened emission of positively charged dark trions when the monolayer is electrostatically doped with holes. Remarkably, the discovered hole-hole assisted luminescence peak emerges in the near-infrared, about 500 meV below the well-studied spectral region of excitons and trions. In magnetophotoluminescence experiments, we find that the $g$-factor of this new transition ($g=+4$) has an opposite sign compared to the well-known $g$-factor of neutral or charged excitons. This allows us to propose a mechanism of brightening of the positively charged dark trion involving the Γ valley of the valence band.

Poor man's Majorana bound states (MBS) arise in minimal Kitaev chains when the parameters are fine-tuned to a sweet spot. We consider an interacting two-site Kitaev chain coupled to a single-mode cavity and show that the sweet spot condition can be controlled with the cavity frequency and the hopping between sites. Furthermore, we demonstrate that photon-mediated effective interactions can be used to screen intrinsic interactions, improving the original quality of the MBS. We describe experimental signatures in the cavity transmission to detect their presence and quality. Our work proposes a new way to tune poor man's MBS in a quantum dot array coupled to a cavity.

Nonreciprocal charge transport (NCT) characterized by unequal resistances for opposite current direction enriches the fundamental physics of electron transport and is promising for potential device applications. Here, we report on a study on the magnetic control of the NCT in two-dimensional systems with different types of spin-orbit coupling (SOC). Based on the Boltzmann transport theory, we first study this effect using a general Hamiltonian model and show that the nonlinear conductivity can be efficiently tuned by the exchange field. In particular, the exchange-field orientation dependence of the nonlinear conductivity reveals significantly distinct relations for different SOCs. We further derive the analytical expressions with the weak-field approximation, which are in good accordance with numerical results. Then, we exemplify this phenomenon in the ${\mathrm{Ag}}_2\mathrm{Te}/{\mathrm{Cr}}_2{\mathrm{O}}_3$ surface based on density functional theory calculations. We predict that the nonlinear conductivity in such a system strongly depends on the surface magnetization orientation of the ${\mathrm{Cr}}_2{\mathrm{O}}_3$ layer. Those findings also suggest that measuring the NCT as a function of the exchange-field orientation provides a simple electrical means to quantify the SOC type. Our results are expected to provide a valuable insight into the NCT physics and open avenues for future rectifying devices.

This study presents an ab initio investigation of the XANES spectra at the aluminum $K$ edge for three compounds: ${\mathrm{Al}}_2{\mathrm{O}}_3, {\mathrm{AlF}}_3$, and ${\mathrm{AlCl}}_3$, where the Al atoms share the same oxidation state (III) and are coordinated in an octahedral symmetry. The XANES spectra calculated within the independent-particle approximation (IPA) reveal significant differences, including shifts in the spectrum onset, variations in the spectral shapes, and the presence of a prepeak in the case of ${\mathrm{AlCl}}_3$, all in correspondence with the behavior of the projected density of states of the absorbing atom in the different materials. The origin of those features can, therefore, be identified in the specific band structure of each compound. When electron-hole interactions are taken into account through the solution of the Bethe-Salpeter equation, a series of dark and bright excitons with large binding energies and Frenkel character is obtained. The strong excitonic effects lead to the suppression of the prepeak in ${\mathrm{AlCl}}_3$ and further accentuate the differences among the three Al $K$-edge spectra, which shows that drawing conclusions solely on the basis of IPA spectra may be misleading.

We present time-domain THz spectroscopy of thin films of the heavy-fermion superconductor ${\mathrm{CeCoIn}}_5$. Below the $\approx 40$ K Kondo coherence temperature, a narrow Drude-like peak forms, as a result of the $f$-orbital–conduction-electron hybridization and the formation of the heavy-fermion state. The complex optical conductivity is analyzed through a Drude model and extended Drude model analysis. Via the extended Drude model analysis, we measure the frequency-dependent scattering rate ($1/\tau$) and effective mass ($m^{*}/m_b$). This scattering rate shows a linear dependence on temperature, which matches the dependence of the resistivity as expected. Nevertheless, the width of the low-frequency Drude peak itself that is set by the renormalized quasiparticle scattering rate ($1/{\tau }^{*}=m_b/m^{*}\tau$) shows a $T^2$ dependence. This is the scattering rate that characterizes the relaxation time of the renormalized quasiparticles. This gives evidence for a Fermi liquid state, which in conventional transport experiments is hidden by the strong temperature dependent mass.

Unlike Hermitian systems, non-Hermitian energy spectra under periodic boundary conditions can form closed loops in the complex energy plane, a phenomenon known as the point-gap topology. In this paper, we investigate the self-intersection points of such non-Hermitian energy spectra and reveal their geometric origins. We rigorously demonstrate that these self-intersection points result from the intersection of the auxiliary generalized Brillouin zone and the Brillouin zone in one-band systems, as confirmed by an extended Hatano-Nelson model. This finding is further generalized to multiband systems, illustrated through a non-Hermitian Su-Schrieffer-Heeger model. Moreover, we address multiple self-intersection points and derive the geometric conditions for general $n$-fold self-intersection points. Our results enhance the fundamental understanding of generic non-Hermitian quantum systems and provide theoretical support for further experimental investigations of energy self-intersection points.

The discovery of the kagome metal ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$ sparked broad interest, due to the coexistence of a charge density wave (CDW) phase and possible unconventional superconductivity in the material. In this Letter, we use low-energy electron diffraction (LEED) with a $\mu \mathrm{m}$-sized electron beam to explore the periodic lattice distortion at the antimony-terminated surface in the CDW phase. We recorded high-quality backscattering diffraction patterns in ultrahigh vacuum from multiple cleaved samples. Unexpectedly, we did not find superstructure reflexes at intensity levels predicted from dynamical LEED calculations for the reported $2\times 2\times 2$ bulk structure. Our results suggest that in ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$ the periodic lattice distortion accompanying the CDW is less pronounced at Sb-terminated surfaces than in the bulk.

We predict the giant ferroelectric control of interfacial properties of $\mathrm{Ni}/{\mathrm{HfO}}_2$, namely, (i) the magnetocrystalline anisotropy and (ii) the inverse spin and orbital Rashba effects. The reversible control of magnetic properties using electric gating is a promising route to low-energy consumption magnetic devices, including memories and logic gates. Synthetic multiferroics, composed of a ferroelectric in proximity to a magnet, stand out as a promising platform for such devices. Using a combination of ab initio simulations and transport calculations, we demonstrate that reversing the electric polarization modulates the interface magnetocrystalline anisotropy from in-plane to out-of-plane. This modulation compares favorably with recent reports obtained upon electromigration induced by ionic gating. In addition, we find that the current-driven spin and orbital densities at the interface can be modulated by about 50% and 30%, respectively. This giant modulation of the spin-charge and orbit-charge conversion efficiencies opens appealing avenues for voltage-controlled spin- and orbitronics devices.

Dirac semimetals are renowned for the host of singular symmetry-protected band degeneracies which can give rise to other exotic phases. In this work, we consider a two-dimensional Dirac semimetal stabilized by $\mathcal{PT}$ symmetry and nonsymmorphic symmetries. We find that an out-of-plane Zeeman field can lift the Dirac points and transform the system into a Chern insulator with chiral edge states. By placing the nonsymmorphic Dirac semimetal in proximity to an $s$-wave superconductor, we uncover that chiral topological superconductors with large Chern numbers can be achieved. In addition, we find that topologically protected Bogoliubov Fermi surfaces can also emerge in this system, due to the coexistence of inversion symmetry and particle-hole symmetry. Notably, we find that the chiral Majorana edge state persists even when the Chern number becomes ill defined due to the appearance of Bogoliubov Fermi surfaces. The impact of these Bogoliubov Fermi surfaces on the thermal Hall effects is also investigated. Our study not only identifies a class of materials capable of realizing topological Bogoliubov Fermi surfaces through conventional $s$-wave superconductivity, but also uncovers an exotic phase where chiral Majorana edge states and Bogoliubov Fermi surfaces coexist.