Detecting spin polarization
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Spin-state effect on the efficiency of a post-synthetic modification reaction on a spin crossover complex
The spin state of a metal center significantly influences the catalytic activity of its complex, a phenomenon so crucial that it has led to the dedicated field of spin catalysis. Here we investigate the effect of the spin state of an iron-based metal complex on the organic reactivity of its ligands. Specifically, we examined the post-synthetic modification of the spin crossover (SCO) complex [Fe(NH2trz)3](NO3)2 with p-anisaldehyde. A series of experiments were performed to study the transformation of the amino groups depending on the spin state of the metal. Owing to the wide thermal hysteresis loop of the SCO complex, both spin states were compared under identical conditions. The results revealed that the high-spin state led to the formation of 1.34 times more imine functional groups than the low-spin state, we propose that this arises from the different interactions between the solvent and the SCO at the different spin states.
Switching on and off the spin polarization of the conduction band in antiferromagnetic bilayer transistors
Antiferromagnetic conductors with suitably broken spatial symmetries host spin-polarized bands, which lead to transport phenomena commonly observed in metallic ferromagnets. In bulk materials, it is the given crystalline structure that determines whether symmetries are broken and spin-polarized bands are present. Here we show that, in the two-dimensional limit, an electric field can control the relevant symmetries. To this end, we fabricate a double-gate transistor based on bilayers of van der Waals antiferromagnetic semiconductor CrPS4 and show how a perpendicular electric displacement field can switch the spin polarization of the conduction band on and off. Because conduction band states with opposite spin polarizations are hosted in the different layers and are spatially separated, these devices also give control over the magnetization of the electrons that are accumulated electrostatically. Our experiments show that double-gated CrPS4 transistors provide a viable platform to create gate-induced conductors with near unity spin polarization at the Fermi level, as well as devices with a full electrostatic control of the total magnetization of the system.
Spin–valley protected Kramers pair in bilayer graphene
The intrinsic valley degree of freedom makes bilayer graphene (BLG) a unique platform for semiconductor qubits. The single-carrier quantum dot (QD) ground state exhibits a twofold degeneracy, where the two states that constitute a Kramers pair have opposite spin and valley quantum numbers. Because of the valley-dependent Berry curvature, an out-of-plane magnetic field breaks the time-reversal symmetry of this ground state and a qubit can be encoded in the spin–valley subspace. The Kramers states are protected against known spin- and valley-mixing mechanisms because mixing requires a simultaneous change of the two quantum numbers. Here, we fabricate a tunable QD device in Bernal BLG and measure a spin–valley relaxation time for the Kramers states of 38 s at 30 mK, which is two orders of magnitude longer than the 0.4 s measured for purely spin-blocked states. We also show that the intrinsic Kane–Mele spin–orbit splitting enables a Kramers doublet single-shot readout even at zero magnetic field with a fidelity above 99%. If these long-lived Kramers states also possess long coherence times and can be effectively manipulated, electrostatically defined QDs in BLG may serve as long-lived semiconductor qubits, extending beyond the spin qubit paradigm.
Targeting macrophage polarization by inhibiting Pim2 alleviates inflammatory arthritis via metabolic reprogramming
Macrophage polarization and energy metabolic reprogramming play pivotal roles in the onset and progression of inflammatory arthritis. Moreover, although previous studies have reported that the proviral integration of Moloney virus 2 (Pim2) kinase is involved in various cancers through the mediation of aerobic glycolysis in cancer cells, its role in inflammatory arthritis remains unclear. In this study, we demonstrated that multiple metabolic enzymes are activated upon Pim2 upregulation during M1 macrophage polarization. Specifically, Pim2 directly phosphorylates PGK1-S203, PDHA1-S300, and PFKFB2-S466, thereby promoting glycolytic reprogramming. Pim2 expression was elevated in macrophages from patients with inflammatory arthritis and collagen-induced arthritis (CIA) model mice. Conditional knockout of Pim2 in macrophages or administration of the Pim2 inhibitor HJ-PI01 attenuated arthritis development by inhibiting M1 macrophage polarization. Through molecular docking and dynamic simulation, bexarotene was identified as an inhibitor of Pim2 that inhibits glycolysis and downstream M1 macrophage polarization, thereby mitigating the progression of inflammatory arthritis. For targeted treatment, neutrophil membrane-coated bexarotene (Bex)-loaded PLGA-based nanoparticles (NM@NP-Bex) were developed to slow the progression of inflammatory arthritis by suppressing the polarization of M1 macrophages, and these nanoparticles (NPs) exhibited superior therapeutic effects with fewer side effects. Taken together, the results of our study demonstrated that targeting Pim2 inhibition could effectively alleviate inflammatory arthritis via glycolysis inhibition and reversal of the M1/M2 macrophage imbalance. NM@NPs loaded with bexarotene could represent a promising targeted strategy for the treatment of inflammatory arthritis.
Full polarization control of photons with evanescent wave coupling in the ultra subwavelength gap of photonic molecules
Polarization of photons plays a key role in quantum optics and light-matter interactions, however, it is difficult to control in nanosystems since the eigenstate of a nanophotonic cavity is usually fixed and linearly polarized. Here, we reveal the polarization control of photons using photonic molecules (PMs) that host supermodes of two coupled nanobeam cavities. In contrast to conventional PMs in a 2D photonic crystal slab, for the two 1D photonic crystal nanobeam cavities the shift and gap between them can be tuned continuously. With an ultra subwavelength gap, the coupling between the two cavities is dominated by the evanescent wave coupling in the surrounding environment, rather not the emission wave coupling for conventional PMs. As such, the non-Hermiticity of the system becomes pronounced, and the supermodes consist of a non-trivial phase difference between bare eigenstates that supports elliptical polarization. We observe that both the polarization degree and polarization angle of the antisymmetric mode strongly depend on the shift and gap between the two cavities, exhibiting polarization states from linear to circular. This full polarization control indicates the great potential of PMs in quantum optical devices and spin-resolved cavity quantum electrodynamics.
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