The spatial distribution of spurious dots in SiMOS single-electron transistors (SETs), fabricated on an industrial 300 mm process line, has been statistically analyzed. To have a deeper understanding of the origin of these spurious dots, we analyzed SETs with three different oxide thicknesses: 8, 12, and 20 nm. By combining spurious dot triangulation cryo measurement with simulations of strain, gate bias, and location of the electron wave function, we demonstrate that most spurious dots are formed through the combined effects of strain and gate bias, leading to variations in the conduction band energy. Despite the similar thermal expansion coefficients of polycrystalline silicon gates and single-crystalline silicon substrates, strain remains a crucial factor in spurious dot formation. This learning can be used to optimize the device design and the oxide thickness, to reduce the density of spurious dot while keeping quantum dot tunability.

In two-dimensional (2D) layered materials, the layer acts as a crucial degree of freedom, enabling the emergence of exotic physical phenomena through its coupling with charge and spin. Here, using first-principles calculations and group theory analysis, we reveal that layer Nernst and layer thermal Hall effects are present in various 2D $A$-type layered antiferromagnets, including the metal $\mathrm{H}{\mathrm{f}}_2\mathrm{S}$, the normal insulator $\mathrm{Cr}{\mathrm{I}}_3$, and the topological insulator $\mathrm{MnB}{\mathrm{i}}_2\mathrm{T}{\mathrm{e}}_4$. The application of an out-of-plane electric field removes the key magnetic group symmetries and breaks the spin degeneracy of the electronic structures in these 2D antiferromagnets. This spin splitting induces an imbalanced distribution of Berry curvature between the top and bottom layers. By quantitatively calculating the layer-resolved Nernst and thermal Hall conductivities, we confirm the existence of nonzero transverse charge and heat currents in response to a longitudinal temperature gradient field. The calculated conductivities are comparable to, or might even exceed, those of previously well-known altermagnets and noncollinear antiferromagnets that exhibit anomalous Nernst and thermal Hall effects. Our findings provide deeper insights into the thermal transport properties of 2D layered antiferromagnets and pave the way for future developments in antiferromagnetic spintronics, spin caloritronics, and layertronics.

Magnetically frustrated triangular lattice materials are predicted to host exotic quantum states in the presence of conduction electrons. Yet, materials wherein the balance between short-range frustrated exchange interactions and long-range Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions can be fine tuned remain rare. Here, we present a comprehensive investigation of the triangular-lattice antiferromagnet ${\mathrm{CeLi}}_3{\mathrm{Bi}}_2$. Heat capacity, electrical resistivity, and nuclear magnetic resonance (NMR) indicate that ${\mathrm{CeLi}}_3{\mathrm{Bi}}_2$ is a low-carrier-density semimetal, in agreement with our band structure calculations. Further, NMR spin-lattice relaxation results reveal competing RKKY interactions and weak Kondo screening. Thermodynamic, magnetization, and neutron diffraction data are well described by an isolated ground-state Kramers doublet that orders antiferromagnetically at $T_N=1.28$ K in a stripe structure, a strong indicator of magnetic frustration. Our combined findings place ${\mathrm{CeLi}}_3{\mathrm{Bi}}_2$ as a promising platform for tuning the interplay between geometric frustration and RKKY physics.

Electrons in quantum matter behave like a fluid when the quantum-mechanical carrier-carrier scattering dominates over other relaxation mechanisms. By combining a microscopic treatment of electron-electron interactions within the random phase approximation with a phenomenological Navier-Stokes-like equation, we predict that in the limit of high temperature and strong Coulomb interactions, both monolayer graphene and bilayer graphene exhibit a universal behavior in dynamic viscosity. We find that the dynamic viscosity to entropy density ratio for bilayer graphene is closer to the holographic bound, suggesting that such a bound might be observable in a condensed matter system. We discuss how this could be observed experimentally using magnetoconductance measurements in a Corbino geometry for a realistic range of temperature and carrier density.

Centrosymmetric ${\mathrm{GdRu}}_2{\mathrm{Si}}_2$ exhibits a variety of multi-$Q$ magnetic states as a function of temperature and applied magnetic field, including a square skyrmion-lattice phase. The material's behavior is strongly dependent on the direction of the applied field, with different phase diagrams resulting for fields applied parallel or perpendicular to the crystallographic $c$ axis. Here, we present the results of muon-spin relaxation (${\mu }^{+}\mathrm{SR}$) measurements on single crystals of ${\mathrm{GdRu}}_2{\mathrm{Si}}_2$. Our analysis is based on the computation of muon stopping sites and consideration of quantum zero-point motion effects of muons, allowing direct comparison with the underlying spin textures in the material. The muon site is confirmed experimentally, using angle-dependent measurements of the muon Knight shift. Using transverse-field ${\mu }^{+}\mathrm{SR}$ with fields applied along either the [001] or [100] crystallographic directions, we distinguish between the magnetic phases in this system via their distinct muon response, providing additional evidence for the skyrmion and meron-lattice phases, while also suggesting the existence of RKKY-driven muon hyperfine coupling. Zero-field ${\mu }^{+}\mathrm{SR}$ provides clear evidence for a transition between two distinct magnetically ordered phases at 39 K.

A quantitative method based on harmonic Hall voltage analysis for measuring gate voltage-driven changes in magnetic anisotropy at ferromagnet/oxide (FM/Ox) interfaces has been developed and experimentally validated. The method involves applying an AC voltage simultaneously across the Hall bar and oxide gate using the same voltage source, measuring the first and second harmonic Hall voltage responses, and performing subsequent data analysis. Measurements conducted at high modulation frequencies primarily probe electrostatic effects while minimizing the influence of slower magnetoionic dynamics. Based on the devised method, the voltage-controlled magnetic anisotropy (VCMA) efficiency for the Co/AlOx interface is found to be approximately $-40$ fJ/(V m), which is in agreement with previous reports. Additionally, this approach enables the measurement of voltage-induced changes in anomalous Hall resistance. The results are interpreted using a spin-dependent screening model, which describes the experimental data remarkably well. The developed methodology applies to a wide range of materials for characterizing and optimizing VCMA and related phenomena in spintronic devices.

${\mathrm{SrTiO}}_3$ is an ${AB\mathrm{O}}_3$ perovskite and nearly ferroelectric insulator that becomes one of the most dilute electron-doped superconductors known. While its superconducting mechanism is still under debate, recent studies have shown a strong connection between its incipient ferroelectricity and superconductivity. Here we induce ferroelectricity through the substitution of the perovskite B site with Zr and observe a ferroelectric transition in $\mathrm{SrT}{\mathrm{i}}_{1-x}{\mathrm{Zr}}_x{\mathrm{O}}_3$ for as low as $x=0.01$. Metallic $\mathrm{SrT}{\mathrm{i}}_{1-x}{\mathrm{Zr}}_x{\mathrm{O}}_{3-\delta }$ is formed through oxygen reduction, and resistive upturns indicative of the polar metal phase are observed at low temperatures. Superconductivity is enhanced up to a factor of 2 for optimal doping, and $T_c$ enhancement decreases for higher Zr concentration. We observe a shift in the superconducting domes, as well as the formation of a superconducting dome with respect to ferroelectric substitution. These findings provide evidence in support of superconductivity driven by quantum critical fluctuations and the two-phonon pairing model in ${\mathrm{SrTiO}}_3$.

Rare-earth tellurides present unique opportunities to explore the interplay between charge density waves (CDWs) and electronic structure in quasi-two-dimensional systems. Unlike their van der Waals counterparts, the rare-earth tritellurides, ditellurides such as ${\mathrm{LaTe}}_2$ feature distinct polar surfaces and Fermi-surface nesting properties. In this paper, we investigate the electronic band structure of ${\mathrm{LaTe}}_2$, distinguishing the surface states from the bulk bands, and enabling the study of the impact of band filling on CDW stability. We uncover the intricate dependence of CDW formation on the electronic environment and highlight the robustness of the CDW order against variations in band filling. The results provide insights into the complex relationship between electronic structure and CDW formation in this class of materials.

We theoretically investigate the Landau levels (LLs) and magneto-optical conductivity of a $d$-wave altermagnet under a perpendicular magnetic field. Our findings indicate that the LLs, in the absence of a Zeeman field and spin-orbit coupling (SOC), are spin-degenerate and exhibit a linear dependence on both the magnetic field and the level index. Within the framework of linear response theory, the analytical optical transition matrix elements yield isotropic selection rules and anisotropic longitudinal magneto-optical conductivity peaks, regardless of whether SOC is considered. Specifically, in the absence of SOC, only the intraband transition can occur, with the selection rule given by $\mathrm{\Delta }n=\pm 1$. The spin-resolved longitudinal magneto-optical conductivities without a Zeeman field alternately coincide ($\mathrm{Re}{\sigma }_{xx}^{\uparrow }=\mathrm{Re}{\sigma }_{yy}^{\downarrow }$ and $\mathrm{Re}{\sigma }_{xx}^{\downarrow }=\mathrm{Re}{\sigma }_{yy}^{\uparrow }$), resulting in identical spin-resolved Hall magneto-optical conductivities ($\mathrm{Im}{\sigma }_{xy}^{\uparrow }=\mathrm{Im}{\sigma }_{xy}^{\downarrow }$). In the presence of SOC, both intraband and interband transitions occur, with selection rules of $\mathrm{\Delta }n=\pm 1$ and $\pm 3$. Notably, the magnitude of the magneto-optical conductivities associated with the transition process of $\mathrm{\Delta }n=\pm 1$ is three orders of magnitude larger than that associated with $\mathrm{\Delta }n=\pm 3$. This distinctive magneto-optical absorption spectrum clearly reflects the structure of the LLs and leads to strong circular dichroism in the altermagnets. Our results elucidate the magneto-optical properties of altermagnets and can be utilized to determine band parameters at zero magnetic field.

We analyze the dynamical pairing susceptibility ${\chi }_{pp}\left({\omega }_m\right)$ at $T=0$ in a quantum-critical metal, where superconductivity emerges out of a non-Fermi-liquid ground state once the attraction exceeds a certain threshold. We obtain ${\chi }_{pp}\left({\omega }_m\right)$ as the ratio of the fully dressed dynamical pairing vertex $\mathrm{\Phi }\left({\omega }_m\right)$ and the bare ${\mathrm{\Phi }}_0\left({\omega }_m\right)$. For superconductivity out of a Fermi liquid, the pairing susceptibility in the normal state is positive above $T_c$, diverges at $T_c$, and becomes negative below it. For superconductivity out of a non-Fermi-liquid, the behavior of ${\chi }_{pp}\left({\omega }_m\right)$ is different in two aspects: (i) it diverges at the onset of pairing at $T=0$ only for a certain subclass of bare ${\mathrm{\Phi }}_0\left({\omega }_m\right)$ and remains nonsingular for other ${\mathrm{\Phi }}_0\left({\omega }_m\right)$, and (ii) below the instability, it becomes a nonunique function of a continuous parameter $\varphi$ for an arbitrary ${\mathrm{\Phi }}_0\left({\omega }_m\right)$. The susceptibility is negative in some range of $\varphi$ and diverges at the boundary of this range. We argue that this behavior of the susceptibility reflects a multicritical nature of a superconducting transition in a quantum-critical metal, where, immediately below the instability, an infinite number of superconducting states emerges simultaneously, exhibiting different amplitudes of the order parameter down to an infinitesimally small one.

The spin properties of charge carriers confined in CuCl semiconductor nanocrystals (NCs) of different sizes (radius from 1.8 nm up to 28 nm) crystallized in a glass matrix are studied experimentally and theoretically. By means of photoluminescence, spin-flip Raman scattering, time-resolved Faraday ellipticity, and time-resolved differential transmission performed at temperatures in the range $1.6-120$ K at magnetic fields up to 8 T, comprehensive information on the Landé $g$ factors as well as the population and spin dynamics is obtained. The spin signals are contributed by confined electrons with a $g$ factor close to 2, which shows a weak increase with decreasing NC size, i.e., increasing electron confinement energy. We revisit the theory of exciton confinement as a whole in spherical NCs within the six-band valence band model in order to describe the size dependence of the $Z_3$ and $Z_{1,2}$ exciton energies in CuCl NCs. We demonstrate theoretically that the stronger increase of the $Z_{1,2}$ energy transitions with decreasing radius can be explained by the strong absorption from the excited exciton state caused by strong heavy hole-light hole mixing in the exciton. The parameters of the six-band Hamiltonian describing both the exciton and hole kinetic energies are estimated from the comparison of the calculated and experimental size dependencies of the exciton transitions. A theoretical model of the size-dependent Landé $g$ factors for electrons and holes confined in spherical NCs of semiconductors with negative spin-orbit splitting of the valence band is developed.

While traditionally regarded as an obstacle to quantum coherence, recent breakthroughs in quantum optics have shown that the dissipative interaction of a qubit with its environment can be leveraged to protect quantum states and synthesize many-body entanglement. Inspired by this progress, here we set the stage for the—as yet uncharted—exploration of analogous cooperative phenomena in hybrid solid-state platforms. We develop a comprehensive formalism for the quantum many-body dynamics of an ensemble of solid-state spin defects interacting with the magnetic field fluctuations of a common solid-state reservoir. Our framework applies to any solid-state reservoir whose fluctuating spin, pseudospin, or charge degrees of freedom generate magnetic fields. To understand whether correlations induced by dissipative processes can play a relevant role in a realistic experimental setup, we apply our model to a qubit array interacting via the spin fluctuations of a ferromagnetic bath. Our results show that the low-temperature collective relaxation rates of the qubit ensemble can display clear signatures of super- and subradiance, i.e., forms of cooperative dynamics traditionally achieved in atomic ensembles. We find that the solid-state analog of these cooperative phenomena is robust against spatial disorder in the qubit ensemble and thermal fluctuations of the magnetic reservoir, providing a route for their feasibility in near-term experiments. Our work lays the foundation for a multiqubit approach to quantum sensing of solid-state systems and the direct generation of many-body entanglement in spin-defect ensembles. Furthermore, we discuss how the tunability of solid-state reservoirs opens up novel pathways for exploring cooperative phenomena in regimes beyond the reach of conventional quantum optics setups.

${\mathrm{Cu}}_2{\mathrm{IrO}}_3$ has attracted recent interest due to its proximity to the Kitaev quantum spin liquid state and the complex structural response observed at high pressures. We use x-ray spectroscopy and scattering as well as electrical transport techniques to unveil the electronic structure of ${\mathrm{Cu}}_2{\mathrm{IrO}}_3$ at ambient and high pressures. Despite featuring a ${\mathrm{Ir}}^{4+}{J}_{\mathrm{eff}}=1/2$ state at ambient pressure, Ir $L_3$-edge resonant inelastic x-ray scattering reveals broadened electronic excitations that point to the importance of Ir $5d$-Cu $3d$ interaction. High pressure first drives an Ir-Ir dimer state with collapsed $\langle \mathbf{L}·\mathbf{S}\rangle$ and $\langle L_z\rangle /\langle S_z\rangle$, signaling the formation of $5d$ molecular orbitals. A novel $\mathrm{Cu}\to \mathrm{Ir}$ charge transfer is observed above 30 GPa at low temperatures, leading to an approximate ${\mathrm{Ir}}^{3+}$ and ${\mathrm{Cu}}^{1.5+}$ valence, with persistent insulating electrical transport seemingly driven by charge segregation of ${\mathrm{Cu}}^{1+}/{\mathrm{Cu}}^{2+}$ ions into distinct sites. Concomitant x-ray spectroscopy and diffraction measurements through different thermodynamic paths demonstrate a strong electron-lattice coupling, with $J_{\mathrm{eff}}=1/2$ and ${\mathrm{Ir}}^{3+}/{\mathrm{Cu}}^{1.5+}$ electronic states occurring only in phases 1 and 5, respectively. Remarkably, the charge-transfer state can only be reached if ${\mathrm{Cu}}_2{\mathrm{IrO}}_3$ is pressurized at low temperature, suggesting that phonons play an important role in the inhibiting this phase. These results point to the choice of thermodynamic path across interplanar collapse transition as a key parameter to access novel states in intercalated iridates.

Discovering quantum orders in mixed many-body systems is an ongoing issue. Very recently, the notion of an intrinsic mixed-state topologically ordered (IMTO) state was proposed. As a concrete example, we observe the emergence of IMTO by studying the toric code system under stochastic maximal decoherence by $ZX$-diagonal type projective measurement without monitoring. We study how the toric code state changes to an IMTO state at the level of the averaged quantum trajectories. This phase transition is understood from the viewpoint of spontaneous symmetry breaking (SSB) of 1-form weak symmetry, that is, the IMTO is characterized by the symmetry restoration from the SSB, which comes from the proliferation of anyons. To understand the emergent IMTO, order and disorder parameters of 1-form symmetry are numerically studied by stabilizer simulation. The present study clarifies the existence of two distinct microscopic string operators for the fermionic anyons, that leads to distinct fermionic strong and weak 1-form symmetries, and also the obtained critical exponents indicate strong relation between IMTO and percolation.

In this paper, we report the temperature-field phase diagram as well as present a comprehensive study of the electronic structure and three-dimensional fermiology of the triangular-lattice magnet ${\mathrm{EuAg}}_4{\mathrm{Sb}}_2$, utilizing quantum oscillation measurements, angle-resolved photoemission spectroscopy, and first-principles calculations. The complex magnetic phase diagram of ${\mathrm{EuAg}}_4{\mathrm{Sb}}_2$ highlights many transitions through nontrivial AFM states. Shubnikov-de Haas and de Haas-van Alphen oscillations were observed in the polarized ferromagnetic state of ${\mathrm{EuAg}}_4{\mathrm{Sb}}_2$, revealing three pairs of distinct spin-split frequency branches with small effective masses. A comparison of the angle-dependent oscillation data with first-principles calculations in the ferromagnetic state and angle-resolved photoemission spectra shows good agreement, identifying tubular hole pockets and hourglass-shaped hole pockets at the Brillouin zone center, as well as diamond-shaped electron pockets at the zone boundary. As the temperature increases, the frequency branches of the tiny hourglass pockets evolve into a more cylindrical shape, while the larger pockets remain unchanged. This highlights that variations in exchange splitting, driven by changes in the magnetic moment, primarily impact the small Fermi pockets without significantly altering the overall band structure. This is consistent with first-principles calculations, which show minimal changes near the Fermi level across ferromagnetic and simple antiferromagnetic states or under varying on-site Coulomb repulsion.

Pyrochlore magnets provide an excellent arena for the realization of various many-body phenomena, such as classical and quantum order-by-disorder, as well as spin-liquid phases described by emergent gauge-field theories. These phenomena arise from competition between different symmetry-breaking magnetic orders. In this paper, we consider a subspace of the most general bilinear nearest-neighbor Hamiltonian on the pyrochlore lattice, parameterized by the local interaction parameter $J_{z\pm }$, where three symmetry-breaking phases converge. We demonstrate that for small values of $|J_{z\pm }|$, a conventional $\mathbf{q}=0$ ordered phase is selected by a thermal order-by-disorder mechanism. For $|J_{z\pm }|$ above a certain finite threshold, a spin-nematic phase is stabilized at low temperatures. Instead of the usual Bragg peaks, the spin-nematic phase features lines of high intensity in the spin structure factor. At intermediate temperatures above the low-temperature orders, a rank-2 U(1) classical spin liquid is realized for all $J_{z\pm }\ne 0$. We fully characterize these phases using classical Monte Carlo simulations and a self-consistent Gaussian approximation.

Skyrmions, as unique wrapped spin textures, hold great potential for next-generation spintronic devices. Here, we reveal the emergence of nontrivial spin textures in the monolayer semiconductor ${\mathrm{LiCrTe}}_2$ through a combination of first-principles calculations and micromagnetic simulations, which evolve into a Néel-type skyrmion crystal (SkX) in response to external magnetic fields at finite temperatures. The monolayer can sustain a high density of skyrmions, reaching up to 0.018 $\mathrm{skyrmions}/\mathrm{n}{\mathrm{m}}^2$ with a diameter of 2.9 nm, which surpasses values in previous reports for semiconductor layers. The synergistic effect of temperature and magnetic field on the formation of a SkX has been identified. Furthermore, we observe an inverse relationship between the electronic band gap and the skyrmion size in the SkX. Notably, the band gap closes and reverses as the size of skyrmions increases when the monolayer is compressed by −3% in-plane biaxial strain, highlighting the tunable interplay between real-space and reciprocal-space spin textures. Our results shed light on the evolution of a SkX in a semiconducting monolayer and demonstrate the transition of topological and electronic properties upon the generation of a SkX, providing valuable insights for experimental realization and future spintronic applications.

The coupling between topological spin textures and conduction electrons can bring about topological transports in noncentrosymmetric systems with Dzyaloshinskii-Moriya interaction, such as the topological Hall effect (THE). In this study, we observed a large THE in centrosymmetric antiferromagnetic (AFM) EuCuSb single crystal, which has been confirmed to possess a magnetic ground state characterized by the coexistence of an up-up-down-down AFM phase and an incommensurate helimagnetic phase. The experimental results showed that for $H//c$, the system exhibits quasiferromagnetic behavior accompanied by significant extrinsic anomalous Hall conductivity and Hall angle. On the other hand, for $H\perp c$, the system underwent a first-order-like metamagnetic transition, accompanied by hysteretic behavior during the magnetization process. The significant THE was observed only between the metamagnetic transition and magnetic saturation, which indicates that an unknown topological magnetic structure is generated after the metamagnetic transition. Our findings provide a deeper understanding of the evolution behavior of the frustrated magnetic structures under magnetic fields in EuCuSb single crystal, which will become an excellent candidate for studying the formation mechanism of topological magnetic structures in centrosymmetric AFM systems.

In the intricate phase diagram of unconventional superconductors characterized by intertwined electronic orders and superconductivity, a key step in understanding the superconducting mechanism is to investigate the parent compounds from which superconductivity emerges through doping or pressure. In this study we employed optical spectroscopy and ultrafast reflectivity measurements to examine the density wave instability in the trilayer nickelate $\mathrm{L}{\mathrm{a}}_4\mathrm{N}{\mathrm{i}}_3{\mathrm{O}}_{10}$, which displays pressure-induced superconductivity up to 30 K. Our optical spectroscopy measurements reveal that $\mathrm{L}{\mathrm{a}}_4\mathrm{N}{\mathrm{i}}_3{\mathrm{O}}_{10}$ behaves as a metal with a high plasma frequency. Upon cooling, we observed a distinct formation of a density wave energy gap in both optical conductivity and pump-probe measurements. The gap feature is more pronounced compared to the bilayer nickelate $\mathrm{L}{\mathrm{a}}_3\mathrm{N}{\mathrm{i}}_2{\mathrm{O}}_7$. Through a comparison of the experimentally determined plasma frequency with first-principles calculations, we classify $\mathrm{L}{\mathrm{a}}_4\mathrm{N}{\mathrm{i}}_3{\mathrm{O}}_{10}$ as a moderately electron-correlated material, resembling the parent compound of iron-based superconductors but exhibiting weaker correlation than the bilayer nickelate $\mathrm{L}{\mathrm{a}}_3\mathrm{N}{\mathrm{i}}_2{\mathrm{O}}_7$. The enhanced gap feature and weaker electronic correlation in $\mathrm{L}{\mathrm{a}}_4\mathrm{N}{\mathrm{i}}_3{\mathrm{O}}_{10}$ may explain its lower superconductivity transition temperature under high pressure. These findings significantly advance our comprehension of the density wave and superconductivity mechanisms in the trilayer nickelate $\mathrm{L}{\mathrm{a}}_4\mathrm{N}{\mathrm{i}}_3{\mathrm{O}}_{10}$.

Topological insulators (TIs) represent a unique class of materials with significant potential for both fundamental research and future applications. The characteristic band inversion in TIs gives rise to unique properties in their bulk states. In this paper, we report exotic features of nontrivial bulk states in a TI β-$\mathrm{A}{\mathrm{g}}_2\mathrm{Se}$. The investigated crystals exhibit resistivity-temperature behavior characteristic of doped semiconductors, with a band gap that aligns well with theoretical electronic structure calculations. Systematic magnetotransport measurements reveal a three-dimensional (3D) anisotropic Fermi pocket resulting from electron doping, indicating that bulk states predominantly contribute to the observed properties. Under parallel magnetic and electric fields, Zeeman splitting is observed, giving a Landé $g$ factor of ∼10. Furthermore, we detect anomalous longitudinal magnetoresistance (MR) dips in the quantum limit when only the lowest Landau level is occupied, which are closely related to the field-induced topological phase transition and reminiscent of the forbidden backscattering in TIs due to the spinor orthogonality. These intriguing transport phenomena combined with theoretical calculations elucidate the topological nature of β-$\mathrm{A}{\mathrm{g}}_2\mathrm{Se}$ as a TI and offer a promising foundation for developing TI-based devices.