We present a combined theoretical and experimental study on the optical conductivity of ${\mathrm{CeIr}}_3{\mathrm{B}}_2$, where quasi-one-dimensional Ce chains form along the $c$ axis of the monoclinic crystal. Significant hybridization-induced features are observed along the Ce chains by broadband infrared spectroscopy, demonstrating mixed-valent behavior over a wide range of temperatures (6–300 K) and energies (up to 0.8 eV). The ferromagnetic transition at 41 K had no noticeable influence on the temperature evolution of the optical conductivity. A comparison with density functional theory plus dynamic mean-field theory calculations demonstrates the quasi-one-dimensional nature of ${\mathrm{CeIr}}_3{\mathrm{B}}_2$ and the local character of the interactions responsible for the electronic renormalization. Furthermore, we demonstrate how the spectroscopic signatures of this mixed-valent compound are captured by theory, providing a clear distinction from the response expected in the integer-valent Kondo regime.

We investigate topological phase transitions in a two-dimensional electron system with cubic Rashba spin-orbit coupling driven by circularly polarized light. Within the Floquet framework, we demonstrate that light-matter interaction induces nontrivial band topology characterized by a quantized anomalous Hall response, with Chern insulating phases of $\mathcal{C}=0,\pm 1,$ and $\pm 3$. These transitions are governed by gap closings at high-symmetry points in the Brillouin zone, controlled by intensity and energy of the incident light. Introducing a weak linear Rashba term displaces Dirac points in momentum space without modifying the topology, whereas a purely linear Rashba system remains topologically trivial $(\mathcal{C}=0)$. When both linear and cubic Rashba couplings are finite, the linear term confines nonzero-Chern phases to narrow parameter windows. In contrast, incorporating a linear Dresselhaus term into the cubic Rashba system can trigger topological transitions even at small coupling strengths. These results clarify the interplay between distinct spin-orbit couplings in Floquet-engineered Chern insulators and offer experimentally relevant pathways for achieving light-controlled topological phases.

Recent spectroscopic studies have uncovered topological surface states and band inversion in $1\mathrm{T}\text{−}{\mathrm{VSe}}_2$, positioning this material at the intersection of correlated electron physics and nontrivial band topology. While previous interpretations attribute these features to surface strain, the microscopic origin of the topological band structure remains unresolved. Here, we present an alternative explanation based on electronic correlations, showing that a negative effective Hubbard interaction $(U_{\mathrm{eff}}$ $< 0)$ applied to the Se 4p orbitals can reproduce the experimentally observed band inversion at both the $\mathrm{\Gamma }$ and $M$ points. Using density functional theory (DFT) calculations with orbital-selective interactions, we demonstrate that this approach naturally gives rise to topological surface states without invoking structural distortions. Our results highlight the crucial role of ligand orbital correlations in shaping band topology and provide a novel framework for understanding and engineering topological phases in chalcogenide-based quantum materials.

Nematicity in LaFeAsO single crystals is studied by means of high-resolution thermal expansion, shear modulus, and elastoresistivity measurements. A softening of the shear modulus $C_{66}$ towards the structural phase transition at $T_{\mathrm{S}}$ is observed. In addition, a similar Curie-Weiss-like divergence of the nematic susceptibilities is found in the temperature dependence of both ${\chi }^{\mathrm{sh}}$ and ${\chi }^{\mathrm{er}}$, which are deduced from the shear modulus (sh) and the elastoresistivity (er) studies, respectively. These observations provide evidence for an electronic origin of nematicity in LaFeAsO. The characteristic energy of the coupling between the lattice and the electronic degrees of freedom is deduced to $\approx 30\mathrm{K}$. The comparison to corresponding measurements on ${\mathrm{BaFe}}_2{\mathrm{As}}_2$ single crystals reveals a very similar temperature dependence of the shear modulus but yields contrasting results for ${\chi }^{\mathrm{er}}$ : In ${\mathrm{BaFe}}_2{\mathrm{As}}_2, {\chi }^{\mathrm{er}}$ diverges similarly as the uncoupled nematicity deduced from the shear modulus data as it is expected from the underlying Landau theory. In contrast, the Weiss temperatures of ${\chi }^{\mathrm{er}}$ and ${\chi }^{\mathrm{sh}}$ are significantly different in LaFeAsO. This difference is at odds with the commonly anticipated theories of resistivity anisotropy and electronic nematicity in iron pnictides.

We present an extension of second-principles density functional theory (SPDFT) to perform time-dependent simulations. Our approach calculates the real-time, real-space evolution of the density matrix using the Liouville-von Neumann equation of motion, enabling the determination of optical and transport properties in very large systems, containing tens of thousands of atoms, on modest computational platforms. Unlike other methods, SPDFT is applicable to a wide range of materials, including both metals and insulators. We demonstrate its capabilities by computing the spectra of ${\mathrm{SrTiO}}_3$, diamond, and metallic lithium. While SPDFT results for ${\mathrm{SrTiO}}_3$ closely match those obtained from DFT with linear perturbation theory, significant improvements are observed for diamond and metallic lithium. In diamond, the inclusion of electron-electron interactions during the density-matrix evolution yields spectra that more accurately reproduce Bethe-Salpeter equation results than perturbative DFT. In lithium, time-dependent SPDFT captures both interband transitions and the Drude peak, enabling detailed ab initio studies of transport properties beyond usual approximations.

This work examines the influence of thickness on the electrical transport properties of mechanically exfoliated two-dimensional ${\mathrm{SnSe}}_2$ nanosheets, derived from the bulk single crystal. Contrary to the conventional trend observed in two-dimensional systems, we find a semiconducting to metallic resistivity behavior with decreasing thickness. The analysis of low-temperature conduction indicates an increased density of states at the Fermi level with decreasing thickness, which is further corroborated by gate bias-dependent conductance measurement. The enhanced conductivity in thinner flake is attributed to the $n$-type doping arising from surface defect states. The presence and evolution of these defect states with thickness are probed by thickness-dependent room-temperature Raman spectroscopy. Our study provides insights into the thickness-dependent electronic transport mechanism of ${\mathrm{SnSe}}_2$ and the crucial role of defect states in governing the observed conductivity behavior.

Due to their diverse adsorption sites with distinct electronic, chemical, and geometrical properties, quasicrystal surfaces serve as a platform for growing novel overlayer structures. Here, we present the growth of ${\mathrm{C}}_{60}$ molecules on a twofold surface of the decagonal Al-Ni-Co quasicrystal, which possesses both periodic and quasiperiodic order. Scanning tunneling microscopy (STM) reveals that the deposited ${\mathrm{C}}_{60}$ preferentially grows along the periodic direction, producing chains of ${\mathrm{C}}_{60}$ molecules arranged in a Fibonacci sequence, a representative of one-dimensional quasicrystalline order. By comparing STM images at submonolayer coverage with the substrate model structure, we identified that ${\mathrm{C}}_{60}$ molecules preferentially adsorb at Ni/Co atomic sites matching the geometry of ${\mathrm{C}}_{60}$ molecules. The ${\mathrm{C}}_{60}$ molecules experience two competing processes: substrate-molecule interactions and molecule-molecule van der Waals interactions, resulting in chains of limited length. These findings provide insights into tailoring molecular assemblies on quasicrystalline templates, with potential applications in nanostructured materials and molecular electronics.

We study the charge transport and thermoelectric properties of a junction comprising a double quantum dot embedded in $\mathsf{T}$-shaped geometry on the interface between two normal/ferromagnetic electrodes and a superconducting lead. We show that the interdot coupling plays a major role in controlling the local and nonlocal transport properties of this setup. For the weak interdot coupling limit, we obtain the interferometric (Fano-type) line shapes imprinted in the quasiparticle spectra, conductances, and Seebeck coefficients. In contrast, for strong interdot coupling, we predict that the local and nonlocal transport coefficients are primarily dependent on the molecular Andreev bound states induced by the superconducting proximity effect simultaneously in both quantum dots.

We study two-dimensional Dirac fermions in a one-dimensional mass superlattice under a perpendicular magnetic field. Using exact solutions for isolated and finite arrays of domain walls, we demonstrate the persistence of Jackiw-Rebbi modes with a field-dependent renormalized velocity. For the periodic case, we adopt a gauge-invariant projection method onto magnetic Bloch states, valid for arbitrary fields and mass profiles, which yields dispersive Landau levels, and confirm its accuracy by comparison with finite arrays spectra. From the miniband spectra we predict modified quantum Hall plateaus and Weiss-like magnetoconductivity oscillations, characterized by a strongly reduced amplitude and a $\pi /2$ phase shift compared to electrostatic superlattices.

Mercury selenide (HgSe) has gained considerable attention in the last few decades due to its promising optoelectronic applications facilitated by the high intrinsic carrier concentration, high mobility, and tunable semimetallic behavior. A comprehensive understanding of the ultrafast relaxation dynamics of the photoexcited carriers is essential to further assess its potential in device applications. Here, we study the ultrafast hot carrier relaxation dynamics in aggregated HgSe nanoparticles film, prepared by drop casting onto a quartz substrate using time-resolved optical pump terahertz probe spectroscopy. Our results show that the relaxation time (${\tau }_{\text{rel}}$) of the photoexcited carriers increases with the pump fluence $\varphi$ and is independent of lattice temperature $T_L$. The observations of longer relaxation time associated with higher pump fluence show that carrier relaxation by emission of optical phonons is the dominant mechanism. We model the relaxation process of the coupled carrier-phonon system with rate equations incorporating electron-phonon scattering rate. The photoconductivity ($\mathrm{\Delta }\sigma ={\sigma }_{\text{pump}\text{on}}-{\sigma }_{\text{pump}\text{off}}$) in both the time and frequency domain is calculated using the Boltzmann transport equation along with the hot carrier temperature ($T_e$) and optical phonon occupation number ($n_q$) evaluated in a self-consistent manner. This is achieved by taking into account the contributions of different charge scattering mechanisms such as neutral impurity scattering, Coulomb scattering, and optical phonon scattering. A quantitative comparison of the time-dependent photoconductivity and the model calculation yields an estimation of optical phonon lifetime, neutral and Coulomb impurity density, and electron-phonon coupling strength. Our study provides insight into the intraband conductivity of the photoexcited carriers in HgSe, essential for its optoelectronic applications.

Surface plasmons have attracted growing interest from the photonics community due to their inherent ability to controllably confine light below the diffraction limit and their direct application in trapping and transporting matter at the nanoscale. This method, known as plasmonic tweezers, employs confined fields generated by either localized plasmons or surface plasmon polaritons (SPP), which originate in the vicinity of nanostructure-based traps or across structureless platforms, respectively. Herein, we present a theoretical method for generating intense light hotspots and engineering their features by overlapping Airy SPPs (ASPP) at a smooth dielectric-metal interface. We coherently add pairs of Hermite-Gauss modes that belong to a complete basis set of finite-energy ASPPs, which yield highly confined plasmonic hotspots ($\approx \lambda /10$) without the need of using any nanostructured platform. Mode order and relative spacing parameters can be used to tailor the intensity and size of said hotspots, largely outperforming their Gaussian-only-based counterparts. Our method opens a promising venue to confine light at the nanoscale using ASPP-based structured light, which helps to advance the development of structureless plasmonic tweezers and holds promising potential for its application in optical signal processing and plasmonic circuitry.

Recent advancements in topological insulators have opened new possibilities for efficient and robust waveguides. The physical width and operating bandwidth are crucial factors for the performance of topological waveguides. While most topological waveguides are confined to narrow regions around the interface, existing large-area waveguides, although offering adjustable physical widths, typically face the challenge of decreasing operating bandwidths as the mode width increases. In this study, we propose a photonic topological heterostructure that creates multiple domain walls supporting topological edge states by alternately arranging unit cells with different topological properties. This design enables broadband, large-area topological waveguides based on the pseudospin Hall effect, overcoming the limitations of narrow operating bandwidths typically observed in large-area topological waveguides. We investigate the influence of waveguide coupling on the photonic band structure and reveal the relationship between the waveguide's physical width and its operating bandwidth. Electromagnetic simulations show that the large-area waveguides in the proposed heterostructure exhibit broad operating bandwidths and excellent robustness, effectively resisting various structural defects. Sensitivity analysis further demonstrates that the heterostructure is not dependent on specific parameter optimizations, indicating its inherent versatility. This work expands design concepts for large-area topological waveguides and provides avenues for developing multifunctional, stable, and flexible topological devices.

We present a constrained random phase approximation (cRPA) method, termed spectral cRPA (s-cRPA), and compare it to established cRPA approaches for scandium and copper by varying the 3d shell filling. The s-cRPA method generally produces larger Hubbard $U$ interaction values compared to conventional approaches. When applied to the realistic system ${\mathrm{CaFeO}}_3$, s-cRPA yields interaction parameters that align more closely with those required within $\mathrm{DFT}+U$ to reproduce the experimentally observed insulating state, addressing the metallic behavior predicted by standard density functionals. We examine the issue of negative interaction values encountered in the projector cRPA method for filled $d$ shells. We show that s-cRPA provides improved numerical stability by preserving electron number conservation, a constraint that is violated in the projector cRPA method. The s-cRPA approach addresses some limitations of standard cRPA methods, particularly the tendency to underestimate U values, suggesting its potential utility for the community. Additionally, we have enhanced our implementation to include computation of multicentre interactions for analyzing spatial decay and developed an efficient low-scaling variant employing a compressed Matsubara grid to obtain full frequency-dependent interactions.

The integrated device of a perovskite solar cell with a Li-ion battery is an innovative solution for decentralized energy storage in smart electronic devices. In this study, we examine the stability of Li ions intercalated in a ${\mathrm{CsPbI}}_3$ perovskite and their effect on the electronic structure of ${\mathrm{Li}}_x{\mathrm{CsPbI}}_3$ compounds using first-principles density functional theory. Our simulations demonstrate that the insertion of Li at concentrations up to $x=1$ into ${\mathrm{CsPbI}}_3$ perovskite is energetically possible. Moreover, we identify that the distortion of the Pb-I octahedra has the strongest impact on the change in the electronic band gap. Specifically, an increase in the amount of intercalated Li causes larger structural distortions, which in turn lead to an increasing band gap as a function of the Li content.

We provide a detailed study of Abelian quasiparticles of valley polarized fractional Chern insulators (FCIs) residing in the top valence band of twisted bilayer ${\mathrm{MoTe}}_2$ (${\mathrm{tMoTe}}_2$) at hole filling ${\nu }_h=2/3$. We construct a tight-binding model of delocalized quasiparticles to capture the energy dispersion of a single quasiparticle. We then localize quasiparticles by short-range delta impurity potentials. Unlike the fractional quantum Hall (FQH) counterpart in the lowest Landau level (LLL), the density profile around the localized FCI quasiparticle in ${\mathrm{tMoTe}}_2$ depends on the location of the impurity potential and loses the continuous rotation invariance. The FCI quasiparticle localized at moiré lattice center closely follows the anyon Wannier state of the tight-binding model of the mobile quasiparticle. Despite of the difference in density profiles, we find that the excess charge around the impurity potential for the ${\nu }_h=2/3$ FCIs in ${\mathrm{tMoTe}}_2$ is still similar to that of the $\nu =2/3$ FQH state in the LLL if an effective magnetic length on the moiré lattice is chosen as the length unit, which allows a rough estimation of the spatial extent of the FCI quasiparticle. Far away from the impurity potential, this excess charge has the tendency to reach $e/3$, as expected for the Laughlin quasiparticle. The braiding phase of two FCI quasiparticles in ${\mathrm{tMoTe}}_2$ also agrees with the theoretical prediction of fractional statistics. We characterize the interaction between two FCI quasiparticles and find a crossover from repulsive to attractive interaction as gate-to-sample distances decreases. Based on the nearly ideal quantum geometry of the top valence band of ${\mathrm{tMoTe}}_2$, we propose a trial wave function for localized FCI quasiparticles, which reproduces the key feature of the density profile around a quasiparticle.

Gauge theories in (1+1) dimension $\left[\right(1+1\left)\mathrm{D}\right]$ have attracted renewed attention partially due to their experimental realizations in quantum simulation platforms. In this work, we revisit the truncated lattice massive Schwinger model and the truncated lattice Abelian-Higgs model in $(1+1)\mathrm{D}$, where to facilitate quantum simulation, the electric field eigenvalues are truncated to a finite subset while preserving the exact gauge and global symmetries. We uncover previously overlooked universal features in these models, including the emergence of a supersymmetric quantum critical point when the Maxwell term's coefficient changes sign. Our primary focus is the truncated lattice Schwinger model at $\theta =0$, a model not equivalent to familiar spin models. We find that upon reversing the sign of the Maxwell term, the second-order charge conjugation symmetry breaking transition (or confinement-deconfinement transition in a sense) can become first-order. Furthermore, the two types of transitions are connected by a supersymmetric critical point in the tricritical Ising universality class. In the case of truncated Abelian-Higgs model at $\theta =0$, which we find to be equivalent to the quantum Blume-Capel model, the very existence of a symmetry-breaking phase requires a negative-sign Maxwell term. Similarly, there is a tricritical Ising point separating first-order and second-order phase transitions.

In this study, we present an ab initio equation of state (EOS) of solid and liquid neon under extreme conditions using quantum molecular dynamics. We calculate the EOS over a wide range of densities and temperatures up to $14{\mathrm{g}/\mathrm{cm}}^3$ and 100 kK, respectively, and obtain the melting curve of neon up to 3.5 TPa using the $Z$ method. We verify our results by reproducing shock Hugoniot and isentropic compression from recent experimental data. In addition, we study the electrical conductivity of neon under different thermodynamic conditions using the Kubo-Greenwood formula, which provides insight into the onset of neon metallization at high pressures. A new mathematically rigorous method is used to evaluate the delta-function broadening in electrical conductivity calculations. We outline the metallization region of neon and explain the absence of neon conductivity in several shock-wave experiments.

Based on the momentum-resolved Boltzmann equation, we provide self-consistent numerical calculations of the dynamics of conduction electrons in thin noble metal films after linear and nonlinear optical excitations with infrared and terahertz frequencies. Focusing exclusively on electron-phonon interaction, orientational relaxation is introduced and acts as dephasing of the optical excitation on a scale of tens of fs. In the linear regime, our numerical results agree with the field-strength-independent orientational relaxation rate and correspondingly fits of experimental data to a Drude model and predict for nonlinear excitations a field-strength-dependent increase of the orientational relaxation rate. In the THz regime, where the orientational relaxation proceeds faster than the oscillation cycle of the excitation THz field, a new high-order dissipative Kerr-type nonlinearity is predicted. This nonlinearity originates from the Pauli blocking included in the electron-phonon scattering and results in a nonlinearly increasing transmission of the film, detectable in experiments.