Materials Science · Cross-listed from physics.optics
Gallium phosphide on insulator for nanophotonics and quantum technologies
Tobias Bucher, Otto Arnold, Muyi Yang et al. (+7 more)
Gallium phosphide is a promising material platform for visible and near-infrared photonics and
quantum technologies owing to its high refractive index, low optical absorption, and strong second-order nonlinearity. Here, we demonstrate the fabrication of GaP-on-
insulator substrates by ion slicing. The splitting depth and exfoliation behavior of bulk GaP are tailored by controlling the He$^{+}$ ion implantation energy and fluence, enabling thin-film transfer onto amorphous substrates by anodic bonding and
plasma-enhanced direct wafer bonding. Channeling Rutherford backscattering spectrometry and X-ray diffraction confirm that the transferred layers retain their single-crystalline structure, while implantation-induced disorder and optical absorption are substantially reduced by annealing at 500 {\deg}C and subsequent polishing. The annealed films exhibit linear optical properties approaching those of bulk GaP. In addition, a (110)-oriented GaP thin film shows the characteristic polarization dependence expected from the zinc-blende second-order nonlinear susceptibility tensor, demonstrating a near-pristine second-order nonlinear response. This flexible fabrication approach enables the integration of high-quality single-crystalline GaP with variable orientation for free-space and integrated nanophotonics as well as nonlinear and
quantum optical devices.
Read the full abstract ▾
All authors Tobias Bucher, Otto Arnold, Muyi Yang, Zifei Zhang, Katsuya Tanaka, Annkathrin Köhler, Berit Marx-Glowna, Duk-Yong Choi, Isabelle Staude, Carsten Ronning
Soft Condensed Matter
Colloidal Systems
Darrell Velegol
This book has one primary goal: To get you moving quickly from learning basic principles of colloid science, to designing colloidal systems for function or motion in the lab. It is not intended to provide encyclopedic knowledge about all aspects of colloid and surface science; rather, I have chosen not to include many topics of genuine importance. In reaching the intended goal, I use two parallel strategies. First, I give practical results that can be used immediately. If there is a cumbersome calculation, I have worked to reframe it into a table or figure. This is the case for Hamaker constants and hydrodynamics of spheroids, for instance. Second, I describe the physics of various colloidal phenomena, so that you as a researcher can think about alternative strategies. In balancing
algorithms with explanations, I provide plug-and-chug example problems to familiarize you with units, constants, and typical values. The practice problems provide extensions to the most basic theory that open new possibilities, while also giving results that are useful in practical and research studies. Throughout the book, I provide data we commonly use for viscosities,
zeta potentials, ionic phenomena, and other parameters. Rather than providing every reference and every technique, I have provided those references and techniques that we most often use in our lab. In the end, this book aims not to be an exhaustive study of colloids, but rather to be a doorway to producing desired colloidal systems as quickly as possible.
Read the full abstract ▾
Soft Condensed Matter
Equilibrium gigahertz acoustics reveals long-range confinement in liquids
Ievgeniia Chaban and Thomas Pezeril
Understanding how the mechanical properties of
liquids confined within nanometer-scale gaps differ from bulk behavior is central to biophysics, lubrication, catalysis, electrochemistry, and surface science. Yet the characterization of ultrathin confined
liquids remains challenging, as many existing approaches rely on destructive or intrusive contact-based techniques, mostly measuring the
liquid flow in the low frequency regime. Here, we present a non-invasive, all-optical technique based on ultrafast
laser ultrasonics that probes confined
liquids at
equilibrium in the gigahertz frequency range. The method measures the phase and amplitude of time-domain Brillouin scattering signals transmitted through
liquid layers whose thickness is varied step by step with subnanometer effective sampling. Supported by numerical modeling of acoustic propagation and optical detection, these signals allow us to extract the thickness-dependent acoustic velocity and attenuation of confined
liquids. We show that nanometric confinement modifies the GHz acoustic response of glycerol, the
liquid crystal 8CB, and a butyl-based ionic
liquid over unexpectedly long spatial scales. These effects extend from a few nanometers to several tens of nanometers and reveal bound interfacial layers, acoustic stiffening, and enhanced solid-like behavior under confinement. Our results open a route to probing
liquid confinement in a scarcely explored regime: dynamically measured at gigahertz frequencies, yet sufficiently weakly perturbative to preserve the
equilibrium confined state.
Read the full abstract ▾
Strongly Correlated Electrons
Long and short time linear response of metals: a geometric approach
Nishchhal Verma and Raquel Queiroz
The time-dependent
quantum geometric tensor, which captures dipole fluctuations of bound electrons, is essential for understanding the electronic properties of
insulators,
superconductors, and flat bands. It is often considered subleading for low-energy descriptions of metals that are dominated by intra-band processes. Here, we revisit this perspective and highlight scenarios where the
quantum geometry of the wavefunctions close to the
Fermi surface plays a significant role. We compute the time-dependent
quantum geometric tensor for metals, explain its divergence, and contrast it against singular
geometric tensors of Dirac and Weyl semi-metals. We identify the ratio of Drude to total spectral weight, $D/\mathcal{S}_1$, as a
lattice-scale probe of bound versus itinerant charge, and quantify it in the kagome metal, where the two van Hove fillings respond differently despite identical
Fermi surfaces.
Read the full abstract ▾
Statistical Mechanics
Gabriele de Mauro, Manas Kulkarni and Satya N. Majumdar
We introduce a
quantum stochastic resetting protocol with uniform
memory, in which each resetting event returns the system to a state visited at a time chosen uniformly from its entire history. The resulting dynamics is nonunitary, non-Markovian and a direct
quantum generalization of the classical preferential relocation model. Working in the energy eigenbasis, we derive the exact
evolution of every density-
matrix element for an arbitrary time-independent
Hamiltonian and show that the
Hamiltonian enters the dynamics only through the corresponding Bohr frequencies. This leads to a natural distinction between two classes of
quantum systems: gapped and gapless. In gapped systems (systems with a discrete energy spectrum), while the diagonal elements remain unchanged, the off-diagonal elements of the density
matrix in the energy eigenbasis decay algebraically with a continuously varying exponent and with an amplitude that oscillates periodically in $\log t$. The system therefore approaches a stationary state that is independent of the resetting rate and retains a strong
memory of the initial state. In gapless systems (systems with a continuous energy spectrum), arbitrarily small Bohr frequencies prevent stationarity. Instead, the position distribution spreads on the universal (ultra-slow) scale $\log(rt)/r$, independently of the initial state and of the details of the
Hamiltonian. We illustrate these results with a two-level system, a harmonic oscillator, and a free
quantum particle, and contrast them with their classical counterparts.
Read the full abstract ▾
Materials Science
Second-Harmonic Imaging of Magnetic Domains in Thin Film Hematite
Holger Mirkes, Johannes Schmuck, Katharina Müller et al. (+7 more)
Hematite is an
antiferromagnetic oxide and candidate altermagnetic
insulator whose Néel order reorients from an easy-axis to an easy-plane phase at the Morin transition. Interpreting altermagnetic transport and
symmetry sensitive optical responses requires knowledge of the Néel vector orientation relative to the
crystal axes and of the domain structure within the probed device. Here, we show that polarization-resolved second-harmonic generation (SHG) microscopy resolves
magnetic symmetry and domains in epitaxial (0001)-oriented hematite films. Across the Morin temperature, the SHG polarization anisotropy evolves from an approximately sixfold pattern consistent with the easy-axis orientation to pronounced twofold patterns consistent with the easy-plane orientation. A
symmetry analysis based on
magnetic-dipole and electric-quadrupole contributions reproduces this
evolution. Importantly, the interference between SHG amplitudes that are odd and even under reversal of the
magnetic order renders opposite Néel-vector orientations optically distinguishable. Consistently, opposite directions of an applied in-plane
magnetic field produce distinct SHG responses in our experiments. Using this
magnetic contrast, we image micrometer-scale domains, their reorganization across the Morin transition, and their reconfiguration under
magnetic and thermal cycling, including a remanent change after cycling through the
spin-flop transition. These results establish SHG microscopy as a local probe of
magnetic symmetry, Néel-vector orientation, and domain
evolution in hematite films.
Read the full abstract ▾
All authors Holger Mirkes, Johannes Schmuck, Katharina Müller, János Papp, Paul Seifert, Matthias Althammer, Hans Huebl, Stephan Geprägs, Alexander W. Holleitner, Christoph Kastl
Strongly Correlated Electrons
Pressure-Driven Evolution of Electronic and Magnetic Correlations in Bilayer Nickelate La3Ni2O7
Jian Zhou, Rui Song and Haiyan Lu
The recent discovery of high-temperature superconductivity in pressurized
bilayer La3Ni2O7 has sparked intense research interest, yet the microscopic mechanism governing its pressure-dependent superconducting transition temperature (Tc) remains elusive. In this work, we investigate the electronic and
magnetic correlations of La3Ni2O7 under high pressure using a combination of density-functional theory (DFT), constrained random phase approximation (cRPA), and dynamical mean-field theory (DMFT). We find that while hydrostatic pressure enhances the interlayer hopping and the bare superexchange energy scale (4t2/U), it simultaneously drives the system toward a more itinerant regime by reducing the relative correlation strength (U/W). Crucially, our results reveal a distinct orbital-selective
evolution: the Ni dx2-y2 states become increasingly itinerant, whereas the Ni dz2 orbitals retain a more localized character. This pressure-induced itinerancy significantly enhances the hybridization between the two, leading to a dramatic amplification of the Kondo-like screening of the local dz2 moments by the itinerant dx2-y2 electrons. Consequently, the effective
magnetic exchange coupling (Jeff), which serves as the pairing glue, is suppressed in the high-pressure regime. Our findings suggest that the monotonic decrease of Tc at high pressures is driven by the dominance of Kondo screening over superexchange interactions, providing a coherent microscopic explanation for the dome-shaped superconducting phase diagram in La3Ni2O7.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Valley-controlled chiral magnetism in transition metal dichalcogenide monolayers
Igor S. Krivenko, Vladimir N. Mantsevich and Dmitry S. Smirnov
We put forward the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction in transition metal dichalcogenide monolayers as a tool to create and control a
chiral magnetic texture. We show that in the
spin-valley locking regime, the RKKY interaction acts as a Dzyaloshinskii-Moriya coupling with an effective
spin rotation period exactly equal to the tripled
lattice constant. Using mean field theory and classical Monte Carlo simulations, we demonstrate that this interaction qualitatively reshapes the phase diagram of atomically thin antiferromagnets. It destroys the chirality-related phase transition by selecting a single chirality value even when the RKKY interaction is small. At the same time, it shifts the Berezinskii-Kosterlitz-Thouless transition associated with
spins orientation to higher temperatures. We argue that the valley degree of freedom of electrons mediating the RKKY interaction provides a powerful control knob for exploring non-universal phase transitions and
quantum spin liquid states in two-dimensional van der Waals
heterostructures.
Read the full abstract ▾
Materials Science · Cross-listed from physics.optics
Direct Wafer Bonding of Crystal-Ion-Sliced GaP Thin Films for Photonic Applications
Hossein Esfandiar, Emanuel Glück, Fabian Ganss et al. (+11 more)
Gallium phosphide (GaP) is a promising material platform for integrated photonics because of its high refractive index, broad optical transparency, and strong second-order nonlinear response. Here, we demonstrate GaP-on-
insulator thin films fabricated by
crystal ion slicing and direct wafer bonding, using fused silica and SiO$_2$/Si/Si thermally oxidized silicon substrates as representative platforms. Unlike GaP thin-film platforms that rely on heteroepitaxial growth or sacrificial-layer release, the presented approach enables the flexible integration of crystalline GaP thin films, independent of both donor and target substrates. Following post-transfer annealing, the films exhibit near-bulk crystalline quality with low residual strain, smooth surfaces suitable for nanophotonic fabrication, and homogeneous bonding interfaces. Furthermore, annealing restores the linear optical dispersion (n and k) approaching that of epitaxially grown GaP with estimated plane wave absorption loss of 0.9 dB/cm at 1550 nm in the telecom C-band. The demonstrated approach establishes a scalable pathway toward high-quality GaP thin-film photonics compatible with versatile heterogeneous integration and back-end-of-line CMOS processing.
Read the full abstract ▾
All authors Hossein Esfandiar, Emanuel Glück, Fabian Ganss, Ulrich Kentsch, Dennis Arslan, Jana Paeschke, Sebastian Ritter, Andreas Ihring, Muyi Yang, Isabelle Staude, Stefan Facsko, Falk Eilenberger, Carolin Rothhardt, Sebastian W. Schmitt
Other Condensed Matter · Cross-listed from quant-ph
Quantum computer-based simulation of Stark many-body localization in a 1D Fermi-Hubbard model
Abdul Kalam, Prasenjit Deb, Akitada Sakurai et al. (+3 more)
Many-body localization (MBL) is a dynamical phenomenon that describes the non-ergodicity of isolated
quantum many-body systems. In contrast to thermalization, this phenomenon leads to a long-lived
memory of initial states of local systems and slow growth of
entanglement. In this work, we study Stark MBL in a 12-
qubit correlated fermionic system described by the one-dimensional
Fermi-Hubbard model using
Hamiltonian simulation on an IBM superconducting
qubit quantum computer. To enable such a computation on current-day noisy hardware, we combine a series of compilation steps, including the use of the
spin-resolved Jordan-Wigner transformation, employing SWAP networks, and integrating a tensor-network-based
quantum circuit optimization routine on top of a standard
circuit optimization pipeline. As a result, there is approximately an 88$\%$ and 87$\%$ reduction in two-
qubit gate count and
circuit depth, respectively. Through such simulations of the real-time dynamics using Trotterized
quantum circuits, we exhibit a crossover from thermalizing dynamics of the system at a weak tilt of the field to a strongly localized behavior at large tilt with short
evolution times. We also
benchmark our obtained results with respect to those from exact simulations.
Read the full abstract ▾
All authors Abdul Kalam, Prasenjit Deb, Akitada Sakurai, Tapan Mishra, V.S. Prasannaa, B. P. Das
Materials Science
Polaron-mediated metal-insulator transition and proton conduction in hydrogenated nickelate perovskites
Hang Ma, Tianxing Ma and Ying Liang
Nickel-based perovskites, owing to their spontaneous hydrogen uptake and the dramatic increase in resistivity upon hydrogenation, have emerged as promising candidates for
proton-conducting fuel
cell electrolytes. However, the mechanism of the hydrogen-induced metal-
insulator transition (MIT) in rare-earth nickelates remains under debate, particularly regarding whether the doped electrons occupy Ni e$_g$ states or O 2p ligand hole states. Here, we reveal a comprehensive MIT mechanism using first-principles calculations on NdNiO$_3$: the electrons introduced by hydrogen doping occupy the O 2p ligand hole states of the Ni-O hybridized d$_8$L configuration, promoting electron-polaron formation. The resulting electron polarons, together with
proton polarons, weaken the Ni-O hybridization and thereby drive the originally itinerant Ni e$_g$ electrons toward localization. This generates a local d8 (t$_{2g}$$^6$e$_g$$^2$) electronic configuration, leading to a Mott transition. In addition, we also find that compared with NdNiO$_3$, SmNiO$_3$ with a smaller A-site ionic radius more readily absorbs hydrogen but exhibits weaker
proton diffusion capability. Hydrogenation promotes
proton permeation along the [001] direction via the intraoctahedral transfer, whereas the overall
proton diffusivity is reduced. These results provide guidance for experimental screening of strongly correlated
oxides as electrolyte materials and offer theoretical insights for enhancing
proton conductivity in rare-earth nickelates.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Proximity effects of chiral magnetization on transition metal dichalcogenides monolayers
Vladimir N. Mantsevich, Igor S. Krivenko and Dmitry S. Smirnov
We consider the proximity effects of a commensurate
chiral $120^{\circ}$ Néel
magnetic structure on the transport and optical properties of a transition metal dichalcogenide monolayer (TMD ML). The enlarged
magnetic unit
cell leads to the folding of the Brillouin zone and enables efficient intervalley
spin-flip scattering. Starting from a six band tight binding model, we develop an effective $k\cdot p$ model, which describes the coupling between charge carriers in the TMD ML and the
chiral magnetization. We predict the anomalous
antiferromagnetic Hall effect (AHE) for conduction electrons and describe it accounting for the interplay between anomalous velocity, side jump, and skew scattering contributions. The proximity of the
chiral magnetization also leads to the mixing and splitting of the
exciton resonances in the two valleys which are related by the time reversal
symmetry despite zero net magnetization. Finally, we demonstrate the possibility to measure the distribution of in-plane orientation of the
chiral magnetization through Faraday rotation and the ellipticity of incident linearly polarized light.
Read the full abstract ▾
Materials Science
Ab initio High-Pressure Phase Diagrams of Al-Mg Alloys in the Low Solute Concentration Limit
Shambhu Bhandari Sharma, Shailesh Mehta and Dario Alfè
Binary
alloy phase diagrams at high pressure are essential for understanding solidification and chemical partitioning in both engineered materials and planetary interiors, yet their experimental determination becomes increasingly challenging under extreme conditions. We apply a fully ab initio approach [J. Chem. Phys. 162, 184502 (2025)], based on density-functional theory, to compute the dilute-limit phase diagram of the Al-Mg system from ambient conditions up to 150 GPa. As a first step, we calculate the melting curves of pure fcc Al and pure hcp/bcc Mg, including the hcp-bcc phase boundary and triple point of Mg, all of which agree closely with available experimental data. The binary phase diagram is then constructed at both compositional extremes. On the Al-rich side, Mg consistently favours the
liquid throughout the entire pressure range, with this preference strengthening monotonically under compression. On the Mg-rich side, Al partitions preferentially into the
liquid at ambient pressure but undergoes a complete reversal above ~60 GPa, becoming solid-favouring as the Mg host transitions from hcp to bcc. This pressure-driven reversal inverts the
topology of the Mg-rich coexistence field from a conventional downward-sloping to an upward-sloping phase boundary, and has direct implications for models of planetary differentiation and interior chemical stratification.
Read the full abstract ▾
Materials Science · Cross-listed from physics.class-ph
Solving the Dissipation Inequality not as a constitutive restriction
Maximiliano Larrain Silva and Amit Acharya
A solution procedure is formulated and solved for treating the nonlinear Dissipation Inequality as a constraint equation within continuum mechanics, and allowing for incomplete knowledge of constitutive behavior. The scheme is demonstrated in the context of the rate-dependent, elastoplastic response of a bar, resulting in a nonlinear problem of constrained optimization. Both closed form and computational results are developed. The computational solutions utilize a sequence of convex optimization problems, and are shown to be accurate. In the example considered, the approach is shown to automatically correct an (intentionally) faulty constitutive specification, resulting in the solution to be in accord with the fundamental postulates of continuum mechanics.
Read the full abstract ▾
Statistical Mechanics
Renormalization-Group Stability Does Not Determine Front Selection
Ko Okumura
The Fisher-Kolmogorov-Petrovsky-Piskunov (FKPP) equation provides a paradigmatic example of front propagation and asymptotic-state selection. Using a unified renormalization-group (RG) framework, we show that its traveling-wave solutions form a continuous family of RG fixed points and that all fronts with v >= 2 are locally RG-stable. The resulting RG stability criterion reproduces the classical linear-stability analysis of Canosa, according to which all fronts with v >= 2 are stable. Nevertheless, the asymptotically selected front is v=2, determined by the leading-edge structure of the initial condition rather than by RG stability. The FKPP equation thus provides an explicit example in which RG fixed-point stability does not determine asymptotic-state selection, demonstrating that stability and selection constitute distinct aspects of RG behavior.
Read the full abstract ▾
Soft Condensed Matter
Direct visualization of local electric fields in a layer of a ferroelectric nematic liquid
Anej Sterle, Natan Osterman, Calum J. Gibb et al. (+4 more)
Ferroelectric nematic
liquids exhibit complex ferroelectric domains shaped by competing elastic and electrostatic interactions. Using fluorescence and polarizing optical microscopy, we investigate domain formation and
evolution under different anchoring conditions. Charged fluorescent ions map the electrostatic potential, revealing that electric fields are localized near domain walls and material surfaces. Upon cooling, domain walls transform from Ising- to Néel-type configurations, lowering the electrostatic potential, and reversibly recover upon heating.
Read the full abstract ▾
All authors Anej Sterle, Natan Osterman, Calum J. Gibb, Jordan Hobbs, Richard J. Mandle, Nerea Sebastián, Alenka Mertelj
Statistical Mechanics · Cross-listed from physics.soc-ph
Microscopic dynamics of consensus formation in multi-agent LLM Naming Games
Cristiano De Nobili, Vijayasri Iyer, Alessandro Codello et al. (+1 more)
Decentralized populations of Large
Language Model (LLM)
agents can spontaneously reach consensus on shared conventions, yet the microscopic mechanisms by which their internal stochasticity shapes macroscopic ordering remain unexplored. We study a minimal LLM Naming Game in which the listener's decision is a single-
token LLM call at decoding temperature $T$, replacing the inventory check of the deterministic Naming Game. Each interaction decomposes into an in-inventory and an out-inventory channel with conditional rates $\pi(T)\!\equiv\!P(\text{YES}\mid w\in P_j)$ and $\phi(T)\!\equiv\!P(\text{YES}\mid w\notin P_j)$, whose balance controls an ordering-disordering drift. A mean-field theory of the two-rate dynamics yields an analytical ordering condition that generalizes the consensus threshold of the
stochastic Naming Game to a critical line in the $(\pi,\phi)$ plane. Across three open-weight architectures, consensus is always reached, but through three distinct listener regimes: permissive (repaint-noise dominated), near-deterministic, and conservative (missed-collapse dominated). The effective finite-size exponent $\beta(T)$ in $t_{\rm conv}\!\sim\!N^{\beta}$ shifts with temperature, and the temperature-sensitivity $\alpha$ in $t_c\!\sim\!e^{\alpha T}$ ranges from ${\approx}\,0.67$ to ${\approx}\,0$ across architectures. Decoding temperature thus emerges as an architecture-dependent control parameter for decentralized LLM populations, quantitatively characterized by the statistical-physics toolkit.
Read the full abstract ▾
All authors Cristiano De Nobili, Vijayasri Iyer, Alessandro Codello, Raffaella Burioni
Mesoscale and Nanoscale Physics
Charge Tunable Optical Nonlinearity of Moiré Exciton-Polaritons
Zhijie Li, Kok Wee Song, Jens-Christian Drawer et al. (+16 more)
Transition metal dichalcogenides represent a versatile platform to study strong light-matter interactions based on
excitons and electrons in ordered
lattices. Twist-engineering of moiré structures further enables the manipulation of the polaritonic nonlinearities via engineering the
exciton landscape on the nanoscale. In this work, we demonstrate in-situ control of the optical saturation-based nonlinearity of moiré
exciton-polaritons by phase space restriction via charge doping. Strong
exciton-
photon coupling is established in a gate-controllable MoTe$_2$-MoSe$_2$ heterobilayer, embedded in a spectrally-tunable open cavity. A small gate voltage can effectively lower the necessary polariton density by one order of magnitude to achieve a similar nonlinear saturation effect as in the charge-neutral case. Our microscopic description successfully explains the observed phenomena in the framework of Pauli blocking for the moiré superlattices with charge preoccupation.
Read the full abstract ▾
All authors Zhijie Li, Kok Wee Song, Jens-Christian Drawer, Vita Solovyeva, Martin Esmann, Niklas Nilius, Muhammad Sufyan Ramzan, Caterina Cocchi, Falk Eilenberger, Takashi Taniguchi, Kenji Watanabe, Atanu Patra, Subhamoy Sahoo, Simon Betzold, Sven Höfling, Alexander Högele, Oleksandr Kyriienko, Christian Schneider, Bo Han
Statistical Mechanics
Inhomogeneous Ising Model on 2D kagomé Lattice: Fermionic field approach
Shahane A. Khachatryan, Zhidong Zhang and Ara G. Sedrakyan
We investigate the two-dimensional inhomogeneous Ising model (2DIM) on the kagom'e
lattice by mapping it onto a particular non-symmetric eight-vertex model and constructing the corresponding $R$-
matrix. Using a fermionic representation, we evaluate the partition function and derive explicit expressions for the main thermodynamic quantities. In the thermodynamic limit, we obtain an exact equation for the critical surface determining the phase transition of the model. We also calculate the free energy, specific heat, and spontaneous magnetization in the
ferromagnetic case. Furthermore, we show that when one or two coupling constants vanish, the model reduces, respectively, to the square-
lattice and one-dimensional Ising models. In both limits, our results reproduce the corresponding exact critical couplings and free energies.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Band topology and symmetry-driven magneto-optical response in two-dimensional d-wave altermagnets with staggered spin-orbit coupling
Meysam Bagheri Tagani Carmine Autieri and Wojciech Brzezicki
Altermagnets combine compensated collinear
magnetic order with momentum-dependent
spin splitting, providing a route to transverse electronic and optical responses without a net
ferromagnetic moment. We develop a strictly periodic four-band tight-binding model for a two-dimensional d-wave altermagnet and distinguish the roles of three
spin orbit coupling (SOC) channels: uniform Rashba SOC, a sublattice-staggered Rashba interaction, and bond-staggered SOC. In the absence of SOC, the d-wave kinetic anisotropy produces
spin-polarized Dirac points on orthogonal Brillouin-zone boundaries, related by the altermagnetic fourfold
spin-group
symmetry. Uniform Rashba SOC mixes the
spin sectors and shifts these nodes but preserves the antiunitary
symmetry that forbids an integrated
Hall response. The sublattice-staggered Rashba term breaks this
symmetry and activates transverse optical response, whereas the bond-staggered SOC provides the mass that gaps the boundary nodes. Their combined action generates strong Berry-
curvature hot spots and, within a narrow parameter window, an isolated lower two-band
manifold with Chern number C=-2. For the representative parameters considered here it is possible to stabilize a Chern
insulator phase. Using covariant-velocity Kubo calculations, we show that large optical
Hall conductivity and circular dichroism extend well beyond the nonzero-Chern region and are controlled by SOC-induced avoided crossings and
symmetry breaking. We further find that carrier doping strongly modifies the resonant and dc
Hall responses through Pauli blocking and the occupation of Berry-
curvature hot spots, enabling gate-controlled sign reversals. These results identify the complementary roles of distinct interfacial SOC mechanisms in producing
topology and tunable magneto-optical activity in compensated two-dimensional magnets.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Time reversal symmetry broken quantum spin hall effect in pseudospin-1 Dirac-Rashba system
Puspita Parui and Bheema Lingam Chittari
The
Quantum spin Hall (QSH) phase is conventionally understood to be protected by time-reversal
symmetry (TRS). Here, we theoretically investigated the fate of the QSH phase in a pseudospin-1 fermionic $\alpha-\mathcal{T}_3$ system in the presence of a TRS-breaking
ferromagnetic exchange field and
spin-nonconserving Rashba
spin-orbit coupling. Despite broken TRS, the QSH phase survives over a finite parameter regime and is characterised by a non-zero projected
spin-Chern number $C_\sigma (\sigma = \uparrow, \downarrow)$, protected by a
spin-spectral gap. In the absence of Rashba coupling, the QSH phase remains robust up to an $\alpha$-dependent critical exchange field. Rashba SOC qualitatively reshapes the phase diagram by driving transitions into two distinct
quantum anomalous
Hall (QAH) phases: a $C=2$ phase, irrespective of $\alpha$-values, and a $C=1$ phase for $\alpha \neq 0,1$, which is further identified as a valley-polarized QAH phase arising from a single valley. Rotating the magnetization to in-plane gaps out the first-order helical edge states and gives rise to second-order topological
insulator (SOTI) phases that host localized corner states in suitable finite geometry. We further identify a topological phase transition between two different SOTI phases, mediated by nanoribbon edge states at an exchange field equal to $\alpha$. These results establish
spin-resolved
topology in a higher pseudospin system as well as the $\alpha-\mathcal{T}_3$
lattice as a versatile platform for engineering and controlling multiple topological phases through
magnetic exchange and
spin-orbit coupling.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Complete Structural Determination of Mesostructural Dodecagonal Quasicrystalline Particles
Xueliang Zhang, Xi Wang, Nobuhisa Fujita et al. (+2 more)
Quasicrystals have revolutionized our understanding of order in solids by demonstrating exotic structural and physicochemical properties with diverse potential applications. Despite the development of various theoretical models and experimental techniques to describe quasicrystal structures, the precise determination of local three dimensional (3D) arrangements of constituent atoms, or of secondary building units such as clusters or micelles, remains elusive. This challenge is particularly acute in self assembled soft matter quasicrystalline systems, where the complex assembly of molecular groups introduces additional defects and structural modulations. Herein, we report the first complete structural determination of self-assembled mesostructural dodecagonal quasicrystalline particles. Employing advanced electron
tomography, combined with dedicated structural tracing and processing workflows, the 3D coordinates of all nodal sites were extracted. This approach reveals that the actual structure deviates from the conventionally assumed tetrahedral close packing geometry, exhibiting diverse coordination environments and displacive fluctuations. We identified and quantified rotational intergrowths arising from node exchange, as well as various defects and disorder, with these features discernible only through 3D analysis. Additionally, we propose a simplified two-layer stacking of isomorphic hexagonal model to form dodecagonal quasicrystal. This work advances our understanding of soft-matter dodecagonal quasicrystals and paves the way for detailed structural elucidation of self-assembled systems.
Read the full abstract ▾
All authors Xueliang Zhang, Xi Wang, Nobuhisa Fujita, Osamu Terasaki, Lu Han
Other Condensed Matter
Coherent migration of the single excitation injected into finite-length segment of the biomolecular chain
D. Chevizovich, V. Matic, Z. Przulj et al. (+1 more)
We study the migration of a single excitation excited at a structural element of a finite molecular segment, which is a part of a long biomolecular chain. The excitation cannot leave the segment and is locally coupled to thermal vibrations of the
lattice, forming a self-trapped state corresponding to a nonadiabatic polaron. The time-dependent probability distribution of finding the excitation at the nodes of the segment is calculated, with particular emphasis on the role of the initial excitation position. A formal analogy is observed between the present model and continuous-time
quantum walk models on finite chains with reflecting boundaries. The results reveal an asymmetry in the probability distribution for nodes symmetrically positioned with respect to the initially excited site, which arises solely from the asymmetric placement of the initial excitation within the finite segment. The only exception occurs when the initially excited node is located at the center of the segment, where the probability distribution becomes symmetric. The complex interference pattern and the absence of well-defined revivals stem from the non-equidistant spectrum of mode frequencies, leading to progressive dephasing of the constituent modes. As a result, the initially well-localized probability maximum fragments into one dominant maximum accompanied by several secondary maxima of lower intensity. These findings highlight the importance of boundary conditions and initial-state geometry in controlling
quantum transport in finite molecular systems.
Read the full abstract ▾
All authors D. Chevizovich, V. Matic, Z. Przulj, S. Galovic
Materials Science · Cross-listed from math.DG
The Primitive and Diamond surfaces locally minimize the variance of Gauss curvature
Hao Chen
We prove that the Schwarz' Primitive (P) and Diamond (D) surfaces are local minimizers of the variance of Gaussian
curvature among local deformations within the
moduli space of triply periodic minimal surfaces of genus 3 (TPMSg3s). Our approach interprets the branch values of the Gauss map as a configuration of eight points on the sphere and expresses the variance of Gaussian
curvature as the product of two integrals involving exponentials of Green's functions. We then show that the Hessian of this functional is positive definite at the cubic configuration when restricted to antipodal deformations, thereby establishing the local minimality of the P and D surfaces. Along the other deformation directions, the Hessian is positive definite except for a two-dimensional eigenspace with slightly negative
eigenvalues, leaving promising hope that the Gyroid is also a local minimizer.
Read the full abstract ▾
Materials Science
Transient Ferromagnetism in Ultrafast Phase Transitions in Perovskites under XUV Irradiation: A Comparative Study of SrTiO3 and KTaO3
Aldo Artimez Pena and Nikita Medvedev
We study ultrafast structural and electronic responses of strontium titanate and potassium tantalate to intense femtosecond irradiation using the XTANT3 multiscale code. It is found that at threshold doses of 0.7 eVatom in STO and 0.9 eVatom in KTO, a superionic state thermally forms with selective melting of the oxygen subsystem while metallic sublattices remain ordered. This state persists up to 1.6 eVatom STO and 1.5 eVatom KTO, above which complete disorder occurs. Analysis of the transient electronic density of states suggests that the B site d orbitals govern the divergent behaviour of the two materials: the compact Ti 3d orbitals in STO produce a narrow conduction band and large intraatomic exchange parameter, driving a transient
ferromagnetic instability on 1 ps timescales, whereas the more spatially extended Ta 5d orbitals in KTO yield a broader conduction band and smaller exchange parameter, keeping KTO paramagnetic. These results suggest d orbital spatial extent as a structural parameter that influences phase transition sequences, and
magnetic response under extreme electronic excitation, with implications for the ultrafast optical control of electronic and
magnetic properties in perovskite based optoelectronic devices. Landau Devonshire analysis shows that irradiation at 0.3 eVatom transiently deepens the polar potential well in unstrained and strained STO and KTO, with the effect amplified approximately 2 fold in strained STO and 6 fold in strained KTO with respect to the unstrained cases.
Read the full abstract ▾
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Adaptive Spectroscopy of Fast Two-Level-System Dynamics in Superconducting Qubits
Fabrizio Berritta, David Pahl, Lukas Pahl et al. (+15 more)
Parasitic two-level-system (TLS) defects are a major source of energy relaxation and temporal instability in superconducting
quantum processors. Our sub-second adaptive spectroscopy reveals telegraphic switching of TLSs with a characteristic timescale of a few seconds and spectral
diffusion with diffusivity $D \approx 0.9~\mathrm{MHz}^2/\mathrm{s}$. These timescales are about $3 \times 10^2$ times faster than what is observed in conventional nonadaptive spectroscopy, which typically requires hours of measurement time. We resolve such fast dynamics on a field-programmable gate array (FPGA)-based controller that enables measurement of frequency- and time-resolved relaxations with sub-second temporal resolution in flux-tunable superconducting
qubits. We observe similar defect dynamics across multiple
qubits in independently fabricated devices measured in different laboratories. We correlate TLS-induced fluctuations with gate-level errors using randomized benchmarking. Our results reveal a previously inaccessible regime of frequency-resolved TLS dynamics and redefine the timescales relevant to TLS-aware characterization and calibration of superconducting
quantum processors.
Read the full abstract ▾
All authors Fabrizio Berritta, David Pahl, Lukas Pahl, William P. Banner, Gabriel Cutter, Jan A. Krzywda, Spencer Weeden, Shravan Patel, Paul Buttles, Stanislav Eilhart, Michael Gingras, Bethany M. Niedzielski, Robert McDermott, Mollie E. Schwartz, Kyle Serniak, Max Hays, Jeffrey A. Grover, William D. Oliver
Materials Science · Cross-listed from quant-ph
Characterizing the nitrogen-vacancy center singlet transition and its phonon sideband for absorption-based room-temperature magnetometry
Tobias Probst, Florian Schall, Sebastian Heuft et al. (+9 more)
Magnetometry with nitrogen-vacancy (NV) centers in diamond has shown great promise in recent years. In particular, absorption-based magnetometry techniques, employing a cavity to enhance the absorption length, can improve the contrast and sensitivity compared to conventional techniques based on reading out the NV$^-$ triplet fluorescence. The absorption techniques rely on
magnetic-field-dependent absorption at the NV$^-$ singlet zero
phonon line at 1042$\,$nm and its
phonon sideband. In a cavity-enhanced spectroscopy approach, we study pump-
laser- and microwave-induced cavity signal changes at room temperature over a spectral range of 680-1050$\,$nm. Through normalization, we eliminate the cavity-enhancement effect and provide quasi-single-pass values for the absorption and optically detected
magnetic resonance (ODMR) contrast. The highest contrast is found at 1042$\,$nm, but multiple points of high contrast are found at the peaks of the
phonon sideband. Additionally, cavity-enhanced ODMR contrasts in the range of 50-80$\,\%$ are presented. We further measure the broadband singlet absorption cross section at room temperature with a novel method through microwave-induced signal changes. This method is insensitive to pump-
laser-induced signal changes by other defects and quantifies the room-temperature absorption strength of the singlet transition and its entire
phonon sideband. We determine the absorption cross section at 1042$\,$nm to be $\sigma^{\,\bigstar}_{1042}=(0.89\pm0.14)\cdot 10^{-21}\,\text{m}^2$ or $\sigma^{\,\blacktriangle}_{1042}=(2.9\pm0.5)\cdot 10^{-21}\,\text{m}^2$. depending on the employed 532$\,$nm NV$^-$ absorption cross section.
Read the full abstract ▾
All authors Tobias Probst, Florian Schall, Sebastian Heuft, Janina J. Schindler, Lukas Lindner, Sven Mägdefessel, Rüdiger Quay, Philipp Reineck, Alexander M. Zaitsev, Takeshi Ohshima, Matthias Weidemüller, Jan Jeske
Superconductivity
Enhanced and robust superconductivity in La0.8Sr0.2NiO2 membranes compressed up to 210 GPa
Shu Cai, Yuqing Tian, Shengjun Yan et al. (+10 more)
The discovery of superconductivity in infinite-layer nickelate thin films has opened a new frontier for exploring unconventional
oxide superconductors beyond the copper
oxide family. However, the presence of substrate hampers investigations under very high pressure. Recently, this problem was circumvented by a study of freestanding Nd0.85Sr0.15NiO2 membranes, which revealed that superconducting transition temperature kept increasing as the pressure was ramped up to 91 GPa, without showing signs of saturation. Naturally, one wonders what would happen at even higher pressures. Here, we report that superconductivity in a freestanding La0.8Sr0.2NiO2 membrane persists under applied ultrahigh pressures up to 210 GPa. The superconducting transition onset temperature exhibits a continuous dome-like
evolution, increasing from 16 K at ambient pressure to a peak of 74.5 K at 146 GPa, and then gradually decreasing to 57.4 K at 210 GPa. Such robustness of superconductivity against ultrahigh pressure has not been observed in high-Tc
oxide superconductors before.
Read the full abstract ▾
All authors Shu Cai, Yuqing Tian, Shengjun Yan, Jinyu Zhao, Bo Hao, Jianfeng Zhang, Shuaihang Sun, Yang Ding, Qi Wu, Ho-kwang Mao, I. Bozovic, Yuefeng Nie, Liling Sun
Mesoscale and Nanoscale Physics
Resolving High-Energy States of Interlayer Excitons in MoSe$_2$/WSe$_2$ Heterostructures
Chirag Chandrakant Palekar, Paulo E. Faria Junior, Tobias Manthei et al. (+8 more)
High-energy states of interlayer
excitons (IXs) in van der Waals
heterostructures remain largely unexplored despite their importance for understanding many-body interactions and nonlinear optical phenomena. Here, we use photoluminescence excitation (PLE) spectroscopy to resolve a Rydberg-like series of excited IX states in MoSe$_2$/WSe$_2$
heterostructures. We observe multiple PLE resonances below the intralayer
exciton energies, which we assign to the 2s-, 3s-, and 4s-like states of the IXs. These resonances are consistently observed across
heterostructures with different twist angles, indicating that the high-energy state spectrum is only weakly affected by the twist angle. Wannier-
exciton calculations incorporating screened Coulomb interactions reproduce the overall energy scale and qualitative trends of the measured Rydberg-like series, supporting the assignment of the observed resonances. Our findings demonstrate that PLE provides direct experimental access to the previously unexplored high-energy IX states in van der Waals
heterostructures.
Read the full abstract ▾
All authors Chirag Chandrakant Palekar, Paulo E. Faria Junior, Tobias Manthei, Maximilian Nagel, Bhabani Sankar Sahoo, Shachi Machchhar, Imad Limame, Martin Podhorský, Jaroslav Fabian, Bárbara Rosa, Stephan Reitzenstein
Mesoscale and Nanoscale Physics
Emission dynamics in zincblende InAsxP1-x quantum dots in InP nanowires: influence of quantum dot size, composition and nanowire geometry
Tomasz Gzyl, Giada Bucci, Krzysztof Gawarecki et al. (+10 more)
Hereby, we present an experimental and theoretical investigation of emission dynamics in zincblende InAsxP1-x
quantum dots (QDs) embedded in InP nanowires (NWs) grown via vapour-
liquid-solid mechanism by chemical beam epitaxy, using Au nanoparticles as a nucleation catalyst. By measuring time-resolved photoluminescence from an ensemble of QD-NWs it was possible to determine the
exciton lifetime dependence on QD composition and height. Changes in the InP shell thickness surrounding the InP NW stem with a QD, brought additional insight into the influence of photonic environment on the carrier dynamics. High-resolution transmission electron microscopy, combined with energy-dispersive X-ray spectroscopy, provided actual structural parameters. The experimentally obtained lifetimes were interpreted in the light of results of 8 band kp calculations combined with configuration-interaction model to take into account the Coulomb interactions and finite-difference time domain photonic simulations to include the effect of optical confinement. The full understanding of the experimental results required considering both, the changes in the QD potential and the Purcell effect, the latter leading to spontaneous emission inhibition in the case of NWs with thin InP shell.
Read the full abstract ▾
All authors Tomasz Gzyl, Giada Bucci, Krzysztof Gawarecki, Elisa García-Tabarés, Anna Musiał, Valentina Zannier, Ylea Vlamidis, Fabio Beltram, Julian V. Montero, Beatriz Galiana, Lucia Sorba, Wojciech Rudno-Rudziński, Grzegorz Sęk