Gauge Structure Research Articles

A model of light pseudoscalar dark matter

The EW-νR model was constructed in order to provide a seesaw scenario operating at the Electroweak scale ΛEW∼246 GeV, keeping the same SM gauge structure. In this model, right-handed neutrinos are non-sterile and have masses of the order ΛEW. They can be searched for at the LHC along with heavy mirror quarks and leptons, the lightest of which has large decay lengths. The model also incorporates a rich scalar sector, consistent with various experimental constraints, predicts a ∼125 GeV scalar with the SM Higgs characteristics satisfying the current LHC Higgs boson data. The seesaw mechanism requires the existence of a complex scalar which is singlet under the SM gauge group. The imaginary part of this complex scalar denoted by As0 is proposed to be the sub-MeV dark matter candidate in this manuscript. We find that the sub-MeV scalar can serve as a viable non-thermal feebly interacting massive particle (FIMP)-DM candidate. This As0 can be a naturally light sub-MeV DM candidate due to its nature as a pseudo-Nambu-Goldstone (PNG) boson in the model. We show that the well-studied freeze out mechanism falls short in this particular framework producing DM overabundance. We identify that the freeze in mechanism produce the correct order of relic density for the sub-MeV DM candidate satisfying all applicable constraints. We also discuss the allowed parameter space arising from the current indirect search bounds for this sub-MeV DM.

Decoding fermion mass pattern from mass hierarchy

Abstract Building an organized Yukawa structure of quarks and leptons is an essential mission to understand fermion mass hierarchy and flavor mixing in particle physics. Inspired by the similarity of CKM and PMNS mixings, a common mass pattern for up-type and down-type quarks, charged leptons, and Dirac neutrinos is realized in terms of hierarchal masses. An organized structure of Yukawa couplings can be expressed on a Yukawa basis. The CKM mixing and PMNS mixing have the same mathematical forms due to SO(2) family symmetry. By fitting the CKM/PMNS mixing experiment, the flat pattern becomes a successful flavor structure. The fundamental fermions can be explained by a new picture to show the relationship between gauge structure and flavor structure.

Fermionic UV models for neutral triple gauge boson vertices

Searches for anomalous neutral triple gauge boson couplings (NTGCs) provide important tests for the gauge structure of the standard model. In SMEFT (“standard model effective field theory”) NTGCs appear only at the level of dimension-8 operators. While the phenomenology of these operators has been discussed extensively in the literature, renormalizable UV models that can generate these operators are scarce. In this work, we study a variety of extensions of the SM with heavy fermions and calculate their matching to d = 8 NTGC operators. We point out that the complete matching of UV models requires four different CP-conserving d = 8 operators and that the single CPC d = 8 operator, most commonly used by the experimental collaborations, does not describe all possible NTGC form factors. Despite stringent experimental constraints on NTGCs, limits on the scale of UV models are relatively weak, because their contributions are doubly suppressed (being d = 8 and 1-loop). We suggest a series of benchmark UV scenarios suitable for interpreting searches for NTGCs in the upcoming LHC runs, obtain their current limits and provide estimates for the expected sensitivity of the high-luminosity LHC.

Thermal Hall effect and neutral spinons in a doped Mott insulator

In the pseudogap phase of the cuprate, a thermal Hall response of neutral objects has been recently detected experimentally, which continuously persists into the antiferromagnetic insulating phase. In this paper, we study the transport properties of neutral spinons as the elementary excitation of a doped Mott insulator, which is governed by a mutual Chern-Simons topological gauge structure. We show that such a chiral spinon as a composite of an S=1/2 spin sitting at the core of a supercurrent vortex, can contribute to the thermal Hall effect, thermopower, and Hall effect due to its intrinsic transverse (cyclotron) motion under internal fictitious fluxes. In particular, the magnitudes of the transport coefficients are phenomenologically determined by two basic parameters: the doping concentration and Tc, quantitatively consistent with the experimental measurements including the signs and qualitative temperature and magnetic-field dependence. Combined with the predictions of the spinon longitudinal transport properties, including the Nernst and spin Hall effects, a phenomenological description of the pseudogap phase is established as characterized by the neutral spinon excitations, which eventually become “confined” with an intrinsic superconducting transition at Tc. Finally, within this theoretical framework, the “order to order” phase transition between the superconducting and antiferromagnetic insulating phases are briefly discussed, with the thermal Hall monotonically increasing into the latter. Published by the American Physical Society 2024

Impact of Forest Management on Wood Production under Climate Change in the Bonis Catchment

The concept of integrated forest management offers a framework for understanding how forest ecosystem services interact with efforts to conserve natural resources. Forests face various disturbances stemming from human activities, management approaches, and shifts in climate patterns. This study aims to explore how forested watersheds respond to diverse silvicultural practices amidst changing climate conditions. The research is centered in the Bonis catchment, situated in the mountainous region of Sila Greca (latitude 39°25′15″ N, longitude 16°12′38″ W) within Southern Italy’s Calabria region. Nearly 93% of the catchment area is cloaked in a forest dominated by approximately 50-year-old Pinus laricio Poiret stands. To model the catchment’s response to various climate and management scenarios, the FEST-FOREST eco-hydrological model, which is distributed and based on physical principles, has been employed. This model accounts for the dynamic interactions between vegetation and the watershed’s hydrological processes. The monitoring of the basin has been ongoing since 1986, with runoff measurements collected at the catchment outlet using dedicated gauging structures. These data have been utilized to calibrate and validate the model, ensuring its accuracy in simulating future scenarios. These simulation results offer stakeholders some qualitative and scientifically based recommendations for the sustainable management of the catchment. In fact, thinning intensity affects hydrological processes, with a 50% stand density reduction identified as a threshold for significant impact on processes like rainfall partitioning and evapotranspiration. Under heavy thinning scenarios, runoff can change by over 60%, and the impact decreases with larger thinning intervals. Furthermore, different climate scenarios influence stem yield levels, with higher production under RCP 4.5 and RCP 8.5 compared to the base climate scenario. In particular, the RCP 8.5 scenario produces the highest yield due to better forest growth under different climate scenarios. This implies the idea that in regions with a Mediterranean climate and coniferous forests, amidst climate change, meticulous forest management involving precisely calibrated thinning schedules and intensities, tailored to unique biotic and abiotic factors, could potentially enhance carbon sequestration while positively influencing runoff rates.

S -wave contribution to rare D0→π+π−ℓ+ℓ− decays in the standard model and sensitivity to new physics

Physics of the up-type flavor offers unique possibilities of testing the standard model (SM) compared to the down-type flavor sector. Here, we discuss SM and new physics (NP) contributions to the rare charm-meson decay D0→π+π−ℓ+ℓ−. In particular, we discuss the effect of including the lightest scalar isoscalar resonance in the SM picture, namely, the f0(500), which manifests in a big portion of the allowed phase space. Other than showing in the total branching ratio at an observable level of about 20%, the f0(500) resonance manifests as interference terms with the vector resonances, such as at high invariant mass of the leptonic pair in distinct angular observables. Recent data from LHCb optimize the sensitivity to P-wave contributions that we analyze in view of the inclusion of vector resonances. We propose the measurement of alternative observables that are sensitive to the S-wave and are straightforward to implement experimentally. This leads to a new set of null observables that vanish in the SM due to its gauge and flavor structures. Finally, we study observables that depend on the SM interference with generic NP contributions from semileptonic four-fermion operators in the presence of the S-wave. Published by the American Physical Society 2024

Sensitivities on the anomalous quartic γγγγ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\gamma \\gamma \\gamma \\gamma $$\\end{document} and γγγZ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\gamma \\gamma \\gamma Z$$\\end{document} couplings at the CLIC

It is essential to directly investigate the self-couplings of gauge bosons in the Standard Model (SM) due to its non-Abelian nature, as these couplings play a significant role in comprehending the gauge structure of the model. The discrepancies between the Standard Model’s expectations and the measured value of gauge boson self-couplings serve as strong evidence for new physics phenomena extending beyond the Standard Model. Such deviations provide valuable insights into the nature of new physics and potentially lead to a deeper understanding of fundamental particles and their interactions. This study examines the sensitivities of anomalous couplings associated with dimension-8 operators that affect the γγγγ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\gamma \\gamma \\gamma \\gamma $$\\end{document} and Zγγγ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z\\gamma \\gamma \\gamma $$\\end{document} quartic vertices. The study focuses on the process e-γ→e-γγ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$e^{-}\\gamma \\rightarrow e^{-}\\gamma \\gamma $$\\end{document} with the incoming photon under Weizsäcker-Williams approximation at the stage-3 scenario of Compact Linear Collider (CLIC) that refers to a CoM energy of 3 TeV. Due to the CLIC options, we take into account both unpolarized and ∓80%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\mp }80\\%$$\\end{document} polarized electron beam with the related integrated luminosities of L=5,4,1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\mathcal {L}}=5, 4, 1$$\\end{document}ab-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ extrm{ab}}^{-1}$$\\end{document} under the systematic uncertainties of δsys=0,3,5\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\delta _{sys}=0, 3, 5$$\\end{document}. Obtained sensitivities on the anomalous quartic gauge couplings (aQGCs) for the process e-γ→e-γγ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$e^{-}\\gamma \\rightarrow e^{-}\\gamma \\gamma $$\\end{document} at s=3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\sqrt{s}}= 3$$\\end{document} TeV and various polarizations are improved by a factor of 2–200 times better for the couplings fT,j/Λ4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$f_{T,j}/\\Lambda ^{4}$$\\end{document} compared with the experimental results reported by CMS Collaboration in Tumasyan et al. (JHEP 10:174, 2021).

Investigation of Floquet engineered non-Abelian geometric phase for holonomic quantum computing

Holonomic quantum computing functions by transporting an adiabatically degenerate manifold of computational states around a closed loop in a control-parameter space; this cyclic evolution results in a non-Abelian geometric phase which may couple states within the manifold. Realizing the required degeneracy is challenging and typically requires auxiliary levels or intermediate-level couplings. One potential way to circumvent this is through Floquet engineering, where the periodic driving of a nondegenerate Hamiltonian leads to degenerate Floquet bands, and subsequently non-Abelian gauge structures may emerge. Here we present an experiment in ultracold Rb87 atoms where atomic spin states are dressed by modulated RF fields to induce periodic driving of a family of Hamiltonians linked through a fully tuneable parameter space. The adiabatic motion through this parameter space leads to the holonomic evolution of the degenerate spin states in SU(2), characterized by a non-Abelian connection. We study the holonomic transformations of spin eigenstates in the presence of a background magnetic field, characterizing the fidelity of these single-qubit gate operations. Results indicate that while the Floquet engineering technique removes the need for explicit degeneracies, it inherits many of the same limitations present in degenerate systems. Published by the American Physical Society 2024

Low‐Roughness 3D‐Printed Surfaces by Ironing for the Integration with Printed Electronics

The roughness of 3D‐printed surfaces poses a challenge when integrating fused filament fabrication (FFF) printing with printed electronics, leading to inconsistencies and breaks in the circuit traces. To improve the surface roughness, an ironing toolpath is proposed. The ironing toolpath involves the hot nozzle going over the printed surface with finer line spacing, remelting the surface to fill gaps, and creating a smooth finish. For further optimization, various ironing parameters are investigated including flow, speed, line spacing, and temperature. A wide range of materials is tested, including commonly used low‐temperature filaments (polylactic acid, polyethylene terephthalate, acrylonitrile butadiene styrene) and high‐temperature filaments (polysulfone, polyetherimide, polyether ether ketone) suitable for integration with printed electronics and medical applications. To collect the extensive datasets, an automated measurement system is deployed. With this method, surface roughness reductions of up to 96.6% are achieved and significant trends are identified. Lastly, the integration of 3D printing with electronics is demonstrated by printing a high‐resolution strain gauge structure on top of an ironed surface and embedding it into fully printed tweezers which can be used in medical robotics. The insights on ironing extend beyond electronics and can also be valuable in other areas where low surface roughness of FFF‐printed parts is required.

Sensitivity of anomalous quartic gauge couplings via tri-photon production at FCC-hh

A direct investigation of the self-couplings of gauge bosons, completely described by the non-Abelian gauge symmetry of the Standard Model, is extremely valuable in understanding the gauge structure of the SM. Any deviation from the SM predictions on gauge boson self-coupling is to give a hint at the existence of a new physics beyond the SM, which is defined with a modification of the self-interactions using an effective field theory approach. In this paper, we present a detailed Monte Carlo study searching for anomalous quartic gauge dimension-8 couplings related to γγγγ and γγγZ vertices at the future hadron-hadron collider (FCC-hh) via tri-photon production at a 100 TeV center of mass energy with an integrated luminosity Lint =30 ab−1. Events that have been parton showered and include detector effects are analyzed with a Toolkit for Multivariate Data Analysis (TMVA) using a boosted decision tree to help distinguish between signal and background events to achieve the best sensitivities on anomalous quartic gauge couplings. Our obtained results reveal that the limits on anomalous quartic gauge couplings fT8/Λ4 and fT9/Λ4 at 95% C.L. without systematic errors are about three orders of magnitude stronger compared to the best current experimental limits reported by the ATLAS collaboration at the LHC. Considering a realistic systematic uncertainty such as 10% from possible experimental sources, our obtained limits of anomalous quartic couplings get worse by about one order of magnitude compared to those without systematic uncertainty but are still two orders of magnitude better than those recently reported by ATLAS.

Analysis of Indonesia’s Railway Track Structure Behavior Under Double-Stack Freight Train Loading

The growing number of freight transported using railway transport is massive. Indonesia targeted 995,500,000 tons of freight transported using the railway mode. Double-stack train is one solution to increase thefreight tonnage of the train without adding the number of operations of the train. The 3D ANSYS model ismade to see the structural behavior of railway tracks under the double-stack train load using 1067 mm and 1435 mm gauge from Indonesia’s railway track regulation. It was also modeled with several speeds to observe its influence on the structure. It is known that in all output parameters of deformation, stress, and strain, the 1435 mm gauge actsbetter for the structure than the 1067 mm gauge. The subgrade service life also became longer in the 1435 mm gauge structure. Lower speed also gives a better impactonthe structure of the track and possible to give longer service life for subgrade.Further research isneeded to observe the railway track structural behavior in cyclic loading and the possibilityofreinforcing the subgrade. The lab-scale test also needed to validate the analysis.

On the Herglotz variational problem

A geometric approach to the Herglotz problem is developed, based on the bundle of affine scalars on the configuration manifold of the given system. The environment, originally introduced to formalize the gauge structure of Lagrangian Mechanics [E. Massa, E. Pagani, and P. Lorenzoni, Transp. Theory Stat. Phys. 29, 69 (2000)], provides the natural setting for the representation of the Herglotz functional as well as for the study of its extremals. Various aspects of the problem are considered: the Lagrangian approach, leading to a generalization of the Poincaré-Cartan algorithm; the parametric approach, involving the introduction of an appropriate super-Lagrangian; the corresponding Hamiltonian and super-Hamiltonian counterparts; the relationship between the Herglotz problem and a constrained variational problem; the evaluation of the abnormality index [Massa et al., Int. J. Geom. Methods Mod. Phys. 12, 1550061 (2015)] of the resulting extremals; the gauge structure of the theory and the consequent existence of Herglotz’s functionals gauge-equivalent to ordinary action functionals.

Non-universal gauge interactions addressing the inescapable link between Higgs and flavour

We systematically explore ultraviolet complete models where flavour hierarchies emerge, via approximate accidental symmetries, from an underlying flavour non-universal gauge structure. In order to avoid large quantum corrections to the Higgs mass, the first layer of non-universality, separating the third generation from the light ones, should appear at the TeV scale. A handful of models survive the combined criteria of naturalness in the Higgs sector, having a semi-simple embedding in the UV, and compatibility with experiments. They all feature quark-lepton unification in the third family and a non-universal electroweak sector. We study in more detail the interesting option of having colour and hypercharge non-universal at the TeV scale, while SU(2)L remains universal up to high scales: this gauge structure turns to be very efficient in secluding the Higgs from large quantum corrections and predicting flavour mixing consistent with data. In all cases, these models imply a rich TeV-scale phenomenology within the reach of near-future direct and indirect experimental searches.

A resin gauge for performance testing of X-ray CT and its calibration by multiple orientation measurements

An accurate and traceable performance testing of the X-ray computed tomography (XCT) is crucial for the application of the XCT in various industrial fields. For the performance testing of the XCT, we proposed a novel gauge with spheres embedded in a cylindrical resin. The proposed gauge is free from the artifacts caused by the gauge structure, and the spheres can be arranged at any position of the gauge. Additionally, the gauge can be placed with different orientations and it can be produced at an economical price. We verified the feasibility of using the proposed gauge as a reference standard, in terms of the coefficient of thermal expansion and secular change of the resin. Furthermore, we developed the associated calibration method for the gauge through multiple orientation measurements using the XCT. From the results, the proposed gauge can be calibrated with an uncertainty of 1.9 μm when the gauge size is 30 mm.

Realistic scheme for quantum simulation of {{mathbb{Z}}}_{2} lattice gauge theories with dynamical matter in (2 + 1)D

Gauge fields coupled to dynamical matter are ubiquitous in many disciplines of physics, ranging from particle to condensed matter physics, but their implementation in large-scale quantum simulators remains challenging. Here we propose a realistic scheme for Rydberg atom array experiments in which a {{mathbb{Z}}}_{2} gauge structure with dynamical charges emerges on experimentally relevant timescales from only local two-body interactions and one-body terms in two spatial dimensions. The scheme enables the experimental study of a variety of models, including (2 + 1)D {{mathbb{Z}}}_{2} lattice gauge theories coupled to different types of dynamical matter and quantum dimer models on the honeycomb lattice, for which we derive effective Hamiltonians. We discuss ground-state phase diagrams of the experimentally most relevant effective {{mathbb{Z}}}_{2} lattice gauge theories with dynamical matter featuring various confined and deconfined, quantum spin liquid phases. Further, we present selected probes with immediate experimental relevance, including signatures of disorder-free localization and a thermal deconfinement transition of two charges.

Non-Abelian gauge structure and flavor mixing in quantum field theory1

The quantum field theory formalism describing the phenomenon of neutrino mixing and oscillations is reviewed in its essential aspects. The condensate structure of the flavor vacuum state is considered and its non-perturbative nature is discussed within the existence in the quantum field theory of the manifold of unitarily inequivalent representations of the anticommutation relations. The Poincaré structure of the theory is discussed in connection with the gauge theory features of neutrino mixing, where the possibility arises to describe flavored neutrinos as on-shell fields with definite masses. The flavor vacuum state may be thought of as a refractive medium where different refraction indexes are related to the different neutrino masses. Neglecting the condensate structure of the flavor vacuum implies neglecting second-order contributions in the gauge field coupling and leads to experimentally inconsistent results.

Complete NLO operators in the Higgs effective field theory

We enumerate the complete and independent sets of operators at the next-to-leading order (NLO) in the Higgs effective field theory (HEFT), based on the Young tensor technique on the Lorentz, gauge, and flavor structures. The operator-amplitude correspondence tells a type of operator forms the on-shell amplitude basis, and for operators involved in Nambu-Goldstone bosons, the amplitude basis is further reduced to the subspace satisfying the Adler zero condition in the soft momentum limit. Different from dynamical fields, the spurion should not enter into the Lorentz sector, instead, it only plays the role of forming the SU(2) invariant together with other dynamical fields. With these new treatments, for the first time, we could obtain the 224 (7704) operators for one (three) generation fermions, 295 (11307) with right-handed neutrinos, and find there were 8 (11) terms of operators missing and many redundant operators can be removed in the effective theory without (with) right-handed neutrinos.

Complete NNLO operator bases in Higgs effective field theory

For the first time, we list the complete and independent set of operators at the next-to-next-to-leading order (NNLO) in the Higgs effective field theory (HEFT). The Young tensor technique utilized in this work guarantees the completeness and independence of the on-shell amplitude basis while the Adler zero condition imposes non-linear symmetry on the Nambu-Goldstone bosons that play the central role in the chiral Lagrangian. The spurion fields are incorporated into the gauge structure of operators following the Littlewood-Richardson rule to accommodate custodial symmetry breaking. We construct 11506 (1927574) NNLO operators for one (three) flavor of fermions for the electroweak chiral Lagrangian with the light Higgs, and enumerate 8065(1179181) operators for one (three) flavor of fermions when the right-handed neutrino is absent by Hilbert series technique. Below the electroweak symmetry breaking scale, the dimension-8 standard model effective field theory (SMEFT) operators could be matched to these HEFT operators at both the NLO and NNLO orders.

Z_{2} Spin Liquids in the Higher Spin-S Kitaev Honeycomb Model: An Exact Deconfined Z_{2} Gauge Structure in a Nonintegrable Model.

The higher spin Kitaev model prominently features the extensive locally conserved quantities the same as the spin-1/2 Kitaev honeycomb model, although it is not exactly solvable. It remains an open question regarding the physical meaning of these conserved quantities in the higher spin model. In this Letter, by introducing a Majorana parton construction for a general spin-S we uncover that these conserved quantities are exactly the Z_{2} gauge fluxes in the general spin-S model, including the case of spin-1/2. Particularly, we find an even-odd effect that the Z_{2} gauge charges are fermions in the half integer spin model, but are bosons in the integer spin model. We further prove that the fermionic Z_{2} gauge charges are always deconfined; hence, the half integer spin Kitaev model would have nontrivial spin liquid ground states regardless of interaction strengths in the Hamiltonian. The bosonic Z_{2} gauge charges of the integer spin model, on the other hand, could condense, leading to a trivial product state, and this is indeed the case at the anisotropic limit of the model.

Dynamical spin-orbit-based spin transistor

Spin-orbit interaction (SOI) has been a key tool to steer and manipulate spin-dependent transport properties in two-dimensional electron gases. Here we demonstrate how spin currents can be created and efficiently read out in nano- or mesoscale conductors with time-dependent and spatially inhomogeneous Rashba SOI. Invoking an underlying non-Abelian SU(2) gauge structure we show how time-periodic spin-orbit fields give rise to spin electric forces and enable the generation of pure spin currents of the order of several hundred nano-Amperes. In a complementary way, by combining gauge transformations with “hidden” Onsager relations, we exploit spatially inhomogeneous Rashba SOI to convert spin currents (back) into charge currents. In combining both concepts, we devise a spin transistor that integrates efficient spin current generation, by employing dynamical SOI, with its experimentally feasible detection via conversion into charge signals. We derive general expressions for the respective spin- and charge conductance, covering large parameter regimes of SOI strength and driving frequencies, far beyond usual adiabatic approaches such as the frozen scattering matrix approximation. We check our analytical expressions and approximations with full numerical spin-dependent transport simulations and demonstrate that the predictions hold true in a wide range from low to high driving frequencies.