Spin-dependent Interactions Research Articles

Interpretation of recently discovered single bottom baryons in the relativistic flux tube model

Following recent experimental progress in the study of bottom baryons, we systematically calculate the mass spectra of Λb, Ξb, Σb, Ξb′, and Ωb baryons with a quark-diquark picture in the framework of a relativistic flux tube model with spin-dependent interactions in the j-j coupling scheme. Furthermore, we calculate the strong decay width of bottom baryons decaying into a bottom baryon and a light pseudoscalar meson. Good agreement is found between the calculated masses and the experimentally available masses of singly bottom baryons. By analyzing both mass spectra and strong decay widths, we interpret Σb(6097) as a 1P(3/2−) state and Ξb(6100) as a 1P(1/2−) state of the Ξb baryon. The Ξb(6227) is identified to be an orbital excitation 1P of the Ξb′ baryon with JP=3/2−. Further, we determine Ξb(6327) and Ξb(6333) as a 1P(3/2−) state and 1P(5/2−) state, respectively, of Ξb′ baryon. From the obtained mass spectra, we construct the Regge trajectories in the (J,M2) plane, which are found to be essentially linear, parallel, and equidistant. Our predictions for higher orbital and radial excited states can help experimentalists identify missing excited states of singly bottom baryons. Published by the American Physical Society 2024

Femtotesla atomic magnetometer with counter-propagating optical sideband pumping.

The ultrasensitive magnetometer has a vital importance in fundamental research and applications. Currently, the spin-exchange relaxation-free (SERF) atomic magnetometer has been reported with a sensitivity around the level of fT/Hz1/2. To enhance the sensitivity, a gradiometer configuration has usually been introduced to cancel the common-mode noise between two separate channels. However, the signal and response from different channels are not the same due to the attenuation of the pump beam. Here, we proposed a counter-propagating optical sideband pumping method to polarize the atoms, using the electro-optic modulator to modulate the single-pump beam, generating two symmetrically red- and blue-detuned sidebands of frequency. This scheme leads to a significant reduction of undesirable effects coming along with the optical pumping, such as light shifts and spatial inhomogeneity in atomic spin polarization. With the help of this pumping scheme, the two channels have the same magnetic response, and we have built a gradiometer atomic magnetometer with a sensitivity of 0.5 fT/Hz1/2 ranging from 5 to 40 Hz. Our results propose the possibility of creating larger arrays of atomic magnetometers (AMs) with high sensitivity and spatial resolution based on single-vapor cells for magnetocardiography and magnetoencephalography imaging or searching for exotic spin-dependent interactions.

Dual-channel intrinsic and nonlinear chirality for an all-optical logic operation.

Chiral metasurfaces hold excellent performance in enhancing spin-dependent light-matter interaction, showing broad application prospects in areas such as chiral imaging, chiral light sources, and chiral sensing. However, utilizing resonant metasurfaces to achieve all-optical logic gates has not been reported yet. In this work, dual-channel intrinsic and nonlinear chiroptical responses are achieved on lithium niobate metasurfaces. The combination of bound states in the continuum (BICs) resonant modes with chiral metasurfaces has revealed its linear and nonlinear chirality. The metasurface achieves linear circular dichroism above 0.9 and nonlinear circular dichroism close to 0.9 on the dual-band. Based on the second-order nonlinear chiroptical response, multiple all-optical logic gates (including NOT, OR, NAND, AND, and NOR) can be realized on the chiral metasurfaces. Our results confirm the operability of resonant metasurfaces in realizing all-optical logic gates, offering a potentially promising approach for the development of new, to the best of our knowledge, all-optical logic devices.

Room temperature polariton spin switches based on Van der Waals superlattices

Transition-metal dichalcogenide monolayers possess large exciton binding energy and a robust valley degree of freedom, making them a viable platform for the development of spintronic devices capable of operating at room temperature. The development of such monolayer TMD-based spintronic devices requires strong spin-dependent interactions and effective spin transport. This can be achieved by employing exciton-polaritons. These hybrid light-matter states arising from the strong coupling of excitons and photons allow high-speed in-plane propagation and strong nonlinear interactions. Here, we demonstrate the operation of all-optical polariton spin switches by incorporating a WS2 superlattice into a planar microcavity. We demonstrate spin-anisotropic polariton nonlinear interactions in a WS2 superlattice at room temperature. As a proof-of-concept, we utilize these spin-dependent interactions to implement different spin switch geometries at ambient conditions, which show intrinsic sub-picosecond switching time and small footprint. Our findings offer new perspectives on manipulations of the polarization state in polaritonic systems and highlight the potential of atomically thin semiconductors for the development of next generation information processing devices.

Light-induced Kondo-like exciton-spin interaction in neodymium(II) doped hybrid perovskite

Tuning the properties of a pair of entangled electron and hole in a light-induced exciton is a fundamentally intriguing inquiry for quantum science. Here, using semiconducting hybrid perovskite as an exploratory platform, we discover that Nd2+-doped CH3NH3PbI3 (MAPbI3) perovskite exhibits a Kondo-like exciton-spin interaction under cryogenic and photoexcitation conditions. The feedback to such interaction between excitons in perovskite and the localized spins in Nd2+ is observed as notably prolonged carrier lifetimes measured by time-resolved photoluminescence, ~10 times to that of pristine MAPbI3 without Nd2+ dopant. From a mechanistic standpoint, such extended charge separation states are the consequence of the trap state enabled by the antiferromagnetic exchange interaction between the light-induced exciton and the localized 4 f spins of the Nd2+ in the proximity. Importantly, this Kondo-like exciton-spin interaction can be modulated by either increasing Nd2+ doping concentration that enhances the coupling between the exciton and Nd2+ 4 f spins as evidenced by elongated carrier lifetime, or by using an external magnetic field that can nullify the spin-dependent exchange interaction therein due to the unified orientations of Nd2+ spin angular momentum, thereby leading to exciton recombination at the dynamics comparable to pristine MAPbI3.

Spin-dependent interactions in orbital-density-dependent functionals: Noncollinear Koopmans spectral functionals

The presence of spin-orbit coupling or noncollinear magnetic spin states can have dramatic effects on the ground-state and spectral properties of materials, in particular on the band structure. Here, we develop noncollinear Koopmans-compliant functionals based on Wannier functions and density-functional perturbation theory, targeting accurate spectral properties in the quasiparticle approximation. Our noncollinear Koopmans-compliant theory involves functionals of four-component orbital densities that can be obtained from the charge and spin-vector densities of Wannier functions. We validate our approach on four emblematic nonmagnetic and magnetic semiconductors where the effect of spin-orbit coupling goes from small to very large: the III-IV semiconductor GaAs, the transition-metal dichalcogenide WSe2, the cubic perovskite CsPbBr3, and the ferromagnetic semiconductor CrI3. The predicted band gaps are comparable in accuracy to state-of-the-art many-body perturbation theory and include spin-dependent interactions and screening effects that are missing in standard diagrammatic approaches based on the random phase approximation. While the inclusion of orbital- and spin-dependent interactions in many-body perturbation theory requires self-screening or vertex corrections, they emerge naturally in the Koopmans-functionals framework. Published by the American Physical Society 2024

Model for bubble nucleation efficiency of low-energy nuclear recoils in bubble chambers for dark matter detection

Bubble chambers are promising technologies for detecting low-energy nuclear recoils from the elastic scattering of dark matter particle candidates. Bubble nucleation occurs when the energy deposition exceeds a specific threshold defined traditionally by the “heat-spike” Seitz threshold. In this paper, we report on a physical model that can account for observed discrepancies between the current Seitz model and the measured nucleation efficiency of low-energy nuclear recoils, which is necessary for interpreting dark matter signals. In our work, we combine molecular dynamics and Monte Carlo simulations together with the Lindhard model to predict bubble nucleation efficiency and energy thresholds for C3F8, CF3I, and xenon with enhanced accuracy over the Seitz model when compared to existing experimental data. We use our model to determine the effect on cross-section limits for spin-dependent and spin-independent interactions and compare it to the current PICO dark matter experiment. Our technique can also be applied to estimate the efficiency of future target fluids where no experimental data are available. As an example, we predict the nucleation efficiency, the energy threshold, and the cross-section limits in the spin-independent channel for the Scintillating Bubble Chamber experiment filled with superheated liquid argon. Published by the American Physical Society 2024

New Classes of Magnetic Noise Self-Compensation Effects in Atomic Comagnetometer.

Precision measurements of anomalous spin-dependent interactions are often hindered by magnetic noise and other magnetic systematic effects. Atomic comagnetometers use the distinct spin precession of two species and have emerged as important tools for effectively mitigating the magnetic noise. Nevertheless, the operation of existing comagnetometers is limited to very low-frequency noise commonly below 1Hz. Here, we report a new type of atomic comagnetometer based on a magnetic noise self-compensation mechanism originating from the destructive interference between alkali-metal and noble-gas spins. Our comagnetometer employing K-^{3}He system remarkably suppresses magnetic noise exceeding 2 orders of magnitude at higher frequencies up to 160Hz. Moreover, we discover that the capability of our comagnetometer to suppress magnetic noise is spatially dependent on the orientation of the noise and can be conveniently controlled by adjusting the applied bias magnetic field. Our findings open up new possibilities for precision measurements, including enhancing the search sensitivity of spin-dark matter particles interactions into unexplored parameter space.

Probing earth-bound dark matter with nuclear reactors

Strongly-interacting dark matter can be accumulated in large quantities inside the Earth, and for dark matter particles in a few GeV mass range, it can exist in large quantities near the Earth’s surface. We investigate the constraints imposed on such dark matter properties by its upscattering by fast neutrons in nuclear reactors with subsequent scattering in nearby well-shielded dark matter detectors, schemes which are already used for searches of the coherent reactor neutrino scattering. We find that the existing experiments cover new parameter space on the spin-dependent interaction between dark matter and the nucleon. Similar experiments performed with research reactors, and lesser amount of shielding, may provide additional sensitivity to strongly-interacting dark matter.

Origin of Exciton-Polariton Interactions and Decoupled Dark States Dynamics in 2D Hybrid Perovskite Quantum Wells.

The realization of efficient optical devices depends on the ability to harness strong nonlinearities, which are challenging to achieve with standard photonic systems. Exciton-polaritons formed in hybrid organic-inorganic perovskites offer a promising alternative, exhibiting strong interactions at room temperature (RT). Despite recent demonstrations showcasing a robust nonlinear response, further progress is hindered by an incomplete understanding of the microscopic mechanisms governing polariton interactions in perovskite-based strongly coupled systems. Here, we investigate the nonlinear properties of quasi-2D dodecylammonium lead iodide perovskite (n3-C12) crystals embedded in a planar microcavity. Polarization-resolved pump-probe measurements reveal the contribution of indirect exchange interactions assisted by dark states formation. Additionally, we identify a strong dependence of the unique spin-dependent interaction of polaritons on sample detuning. The results are pivotal for the advancement of polaritonics, and the tunability of the robust spin-dependent anisotropic interaction in n3-C12 perovskites makes this material a powerful choice for the realization of polaritonic circuits.

Ab initio calculations on magnetic and optical characteristics of pure ZnO and Mn(II)-doped ZnO monolayers with and without neutral charged vacancies defects

At high Curie temperatures, diluted magnetic semiconductors exhibit induced ferromagnetism and spin-dependent interactions, making them useful in magneto-electronic devices. In spite of the fact that ferromagnetism and optical emission dynamics are characterized by intricate microstructural and compositional features, the origins of these phenomena are not yet completely understood. Here, we used first principles calculations to study how vacancy defects affect the electrical, optical, and magnetic properties of pure ZnO and Mn@ZnO monolayers. In the pristine monolayer, the Zn vacancy produces magnetism with a total magnetic moment of 2 μB, but the oxygen vacancy does not. The magnetic semiconducting characteristic of the Mn substitution at the Zn site is shown by a total magnetization of 5 μB. The magnetic ground state of the ZnO monolayer doped with Mn is significantly influenced by the presence of native defects. More specifically, Zn vacancies are essential for stabilizing the FM states due to the bound magnetic polarons (BMPs) formation, but O vacancies have no influence on the magnetic ground state of the Mn(II)@ZnO monolayer. Based on the optical study, we discovered that Zn and O vacancies in the ZnO ML produce optical absorption peaks at 1.92 eV and 2.90 eV, respectively. The substitution of Mn(II) at Zn site not only increases the band gap of the ZnO monolayer but also produces d-d transition bands at lower energy side of fundamental energy gap peak. The Zn vacancies in the Mn(II)@ZnO ML produce an infrared absorption band around 1.13 eV, which could be due to the formation of the BMP, and enhance the optical absorption efficiency. The ZnO ML’s energy gap and Mn ion’s d-d transition bands exhibit a blueshift in AFM systems and a redshift in the FM systems. In far configuration, the Mn(II)@ZnO monolayer show no shift in the fundamental bandgap and intra-band transition of the Mn(II) spins due to the Mn(II) ion’s paramagnetic nature.

Charge amplification in low pressure CF4:SF6:He mixtures with a multi-mesh ThGEM for directional dark matter searches

The CYGNO collaboration is developing next generation directional Dark Matter (DM) detection experiments, using gaseous Time Projection Chambers (TPCs), as a robust method for identifying Weakly Interacting Massive Particles (WIMPs) below the Neutrino Fog. SF6 is potentially ideal for this since it provides a high fluorine content, enhancing sensitivity to spin-dependent interactions and, as a Negative Ion Drift (NID) gas, reduces charge diffusion leading to improved positional resolution. CF4, although not a NID gas, has also been identified as a favourable gas target as it provides a scintillation signal which can be used for a complimentary light/charge readout approach. These gases can operate at low pressures to elongate Nuclear Recoil (NR) tracks and facilitate directional measurements. In principle, He could be added to low pressure SF6/CF4 without significant detriment to the length of 16S, 12C, and 19F recoils. This would improve the target mass, sensitivity to lower WIMP masses, and offer the possibility of atmospheric operation; potentially reducing the cost of a containment vessel. In this article, we present gas gain and energy resolution measurements, taken with a Multi-Mesh Thick Gaseous Electron Multiplier (MMThGEM), in low pressure SF6 and CF4:SF6 mixtures following the addition of He. We find that the CF4:SF6:He mixtures tested were able to produce gas gains on the order of 104 up to a total pressure of 100 Torr. These results demonstrate an order of magnitude improvement [1] in charge amplification in NID gas mixtures with a He component.

A novel non-adiabatic spin relaxation mechanism in molecular qubits.

The interaction of electronic spin and molecular vibrations mediated by spin-orbit coupling governs spin relaxation in molecular qubits. We derive an extended molecular spin Hamiltonian that includes both adiabatic and non-adiabatic spin-dependent interactions, and we implement the computation of its matrix elements using state-of-the-art density functional theory. The new molecular spin Hamiltonian contains a novel spin-vibrational orbit interaction with a non-adiabatic origin, together with the traditional molecular Zeeman and zero-field splitting interactions with an adiabatic origin. The spin-vibrational orbit interaction represents a non-Abelian Berry curvature on the ground-state electronic manifold and corresponds to an effective magnetic field in the electronic spin dynamics. We further develop a spin relaxation rate model that estimates the spin relaxation time via the two-phonon Raman process. An application of the extended molecular spin Hamiltonian together with the spin relaxation rate model to Cu(II) porphyrin, a prototypical S = 1/2 molecular qubit, demonstrates that the spin relaxation time at elevated temperatures is dominated by the non-adiabatic spin-vibrational orbit interaction. The computed spin relaxation rate and its magnetic field orientation dependence are in excellent agreement with experimental measurements.

Searching for exotic spin-dependent interactions with diamond-based vector magnetometer

We propose a new method to search for exotic spin-spin interactions between electrons and nucleons using a diamond-based vector magnetometer. The vector magnetometer can be constructed from ensembles of nitrogen-vacancy centers along different axes in a diamond. The N14 nuclear spins of nitrogen-vacancy centers in the same diamond can be polarized through the dynamic nuclear polarization method to serve as spin sources. With the vector magnetometer, the sought-after exotic interactions can be distinguished from the magnetic dipole-dipole interaction. For the axion-mediated interaction VPP, new upper bounds of the coupling |gPegPN| are expected within the force range from 10 nm to 100 μm. For the Z′-mediated interaction VAA, new upper bounds of the coupling |gAegAN| are expected within the force range from 10 nm to 1 cm. The new upper bounds for VPP and VAA are both expected to be more than 5 orders of magnitude more stringent than existing constraints at the force range of 1 μm with the total measurement time of 1 day. Published by the American Physical Society 2024

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Stability and dynamics of self-bound state of spin–orbit coupled spin-1 Bose–Einstein condensates

We study self-bound state of spin–orbit (SO) coupled spin-1 BECs under the action of the SO coupling and the density-dependent and spin-dependent interactions. The phase transition conditions from the magnetized phase to the unmagnetized phase are analytically obtained in the self-bound state, and the physical mechanism of the phase transition is revealed. The distinct properties of self-bound state in different ground states are discussed in detail, and static and moving self-bound states are obtained. Then, the stability of the self-bound state is studied, and the unstable threshold caused by the competition among SO coupling, Raman coupling, spin-dependent interaction and density-dependent interaction is obtained analytically and confirmed numerically. Furthermore, the dynamical transition of self-bound state from moving type to static type is studied numerically. Due to the spin momentum locking and the drive of spin dynamics, the self-bound states exhibit distinct dynamical behaviors in different ground state phases. Our study provides theoretical evidence for a deep understanding of the stability and the dynamic of self-bound states in SO coupled spin-1 BECs.

Renormalized Kalb-Ramond model: Duality and generalized potential

Considering the recent advances, the weak correlation between the massive Kalb-Ramond and the Proca models is investigated using a set of complementary quantum field techniques beyond the semi-classical approach. A consistent framework to discuss the abrupt degree of freedom variation in the massless limit is established. In this manner, the Stueckelberg procedure is generalized for the present case to derive Ward-Takahashi constraints even for the massive case. By adding couplings with fermionic matter fields, even the weak dual correlation is broken due to the explicit form of the radiative corrections. However, considering the master action approach, the fermionic 1(PI) functions of the Proca electrodynamics are reproduced in all orders of perturbation. A well-defined procedure to eliminate non-desirable extra modes induced by the quantum corrections is successfully applied to this model. Last but not least, we prove that this structure can also provide a spin-dependent interaction that is relevant even at macroscopic distances, being a completion for a recently proposed confining potential.

Low-energy spin-polarized electrons: their role in surface physics

Low-energy (∼100eV) electrons have been employed for more than half a century to investigate physical, chemical and electronic phenomena in condensed matter and surface physics. A particular role may be attributed to a purely quantum-mechanical property of the electron–its spin or intrinsic angular momentum. Since the 1970s the electron spin has been indispensable in determining the role of spin-dependent interactions, such as exchange interaction and spin-orbit coupling and their consequences. Most recently, the aspect of topology and its role in condensed matter systems has given a new drive to the investigation of the electron spin and spin textures in such materials. New results on time-dependent ultrafast phenomena may become available by the availability of new intense lasers and laser-driven sources.

Ultrafast all-electrical universal nanoqubits

We propose how to create, control, and read out real-space localized spin qubits in proximitized finite graphene nanoribbon (GNR) systems using purely electrical methods. Our proposed are formed of in-gap singlet-triplet states that emerge through the interplay of Coulomb and relativistic spin-dependent interactions in GNRs placed on a magnetic substrate. Application of an electric field perpendicular to the GNR heterostructure leads to a sudden change in the proximity couplings, i.e., a quantum quench, which enables us to deterministically rotate the nanoqubit to any arbitrary point on the Bloch sphere. We predict these spin qubits to undergo Rabi oscillations with optimal visibility and frequencies in excess of 10 GHz. Our findings open up an avenue for the realization of graphene-based quantum computing with ultrafast all-electrical methods. Published by the American Physical Society 2024

Exotic spin-dependent interactions through unparticle exchange

The potential discovery of unparticles could have far-reaching implications for particle physics and cosmology. For over a decade, high-energy physicists have extensively studied the effects of unparticles. In this study, we derive six types of nonrelativistic potentials between fermions induced by unparticle exchange in coordinate space. We consider all possible combinations of scalar, pseudo-scalar, vector, and axial-vector couplings to explore the full range of possibilities. Previous studies have only examined scalar-scalar (SS), pseudoscalar-pseudoscalar (PP), vector-vector (VV), and axial-axial-vector (AA) type interactions, which are all parity even. We propose SP and VA interactions to extend our understanding of unparticle physics, noting that parity conservation is not always guaranteed in modern physics. We explore the possibilities of detecting unparticles through the long-range interactions they may mediate with ordinary matter. Dedicated experiments using precision measurement methods can be employed to search for such interactions. We discuss the properties of these potentials and estimate constraints on their coupling constants based on existing experimental data. Our findings indicate that for some particular values of the scaling dimension dU\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {d}_{\\mathcal{U}} $$\\end{document}, the coupling between scalar or vector unparticles and fermions is constrained by several orders of magnitude more tightly than the previous limits. The underlying reason for this improvement is analyzed. Limits are also set on the newly proposed SP and VA interactions for continuous dU\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {d}_{\\mathcal{U}} $$\\end{document} values, allowing the exploration of the dU\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {d}_{\\mathcal{U}} $$\\end{document} dependence of the constraints. It turns out that the bounds exhibit an exponential decay trend with the increasing dU\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {d}_{\\mathcal{U}} $$\\end{document}.