We report dissipative magnon-photon coupling caused by the cavity Lenz effect, where the magnons in a magnet induce a rf current in the cavity, leading to a cavity backaction that impedes the ...magnetization dynamics. This effect is revealed in our experiment as level attraction with a coalescence of hybridized magnon-photon modes, which is distinctly different from level repulsion with mode anticrossing caused by coherent magnon-photon coupling. We develop a method to control the interpolation of coherent and dissipative magnon-photon coupling, and observe a matching condition where the two effects cancel. Our work sheds light on the so-far hidden side of magnon-photon coupling, opening a new avenue for controlling and utilizing light-matter interactions.
We reveal the cooperative effect of coherent and dissipative magnon-photon couplings in an open cavity magnonic system, which leads to nonreciprocity with a considerably large isolation ratio and ...flexible controllability. Furthermore, we discover unidirectional invisibility for microwave propagation, which appears at the zero-damping condition for hybrid magnon-photon modes. A simple model is developed to capture the generic physics of the interference between coherent and dissipative couplings, which accurately reproduces the observations over a broad range of parameters. This general scheme could inspire methods to achieve nonreciprocity in other systems.
By engineering an anti-parity-time (anti-PT ) symmetric cavity magnonics system with precise eigenspace controllability, we observe two different singularities in the same system. One type of ...singularity, the exceptional point (EP), is produced by tuning the magnon damping. Between two EPs, the maximal coherent superposition of photon and magnon states is robustly sustained by the preserved anti-PT symmetry. The other type of singularity, arising from the dissipative coupling of two antiresonances, is an unconventional bound state in the continuum (BIC). At the settings of BICs, the coupled system exhibits infinite discontinuities in the group delay. We find that both singularities coexist at the equator of the Bloch sphere, which reveals a unique hybrid state that simultaneously exhibits the maximal coherent superposition and slow light capability.
Cavity magnon polaritons are mixed quasiparticles that arise from the strong coupling between cavity photons and quantized magnons. Combining high-speed photons with long-coherence-time magnons, such ...polaritons promise to be a potential candidate for quantum information processing. For harnessing coherent information contained in spatially distributed polariton states, it is highly desirable to manipulate cavity magnon polaritons in a two-dimensional system. Here, we demonstrate that tunable cavity magnon polariton transport can be achieved by strongly coupling magnons to microwave photons in a cross-cavity. An analog to the dynamic Hall effect has been demonstrated in a planar cavity spintronic device, where the propagation of cavity-magnon-polaritons is deflected transversally due to hybrid magnon-photon dynamics. Implementing this device as a Michelson-type interferometer using the coherent nature of the dynamic Hall and longitudinal signals, we have developed a proof-of-principle logic device to control the amplitude of cavity-magnon-polaritons by encoding the input microwave phase.
Multifold degenerate points in the electronic structure of metals lead to exotic behaviors. These range from twofold and fourfold degenerate Weyl and Dirac points, respectively, to sixfold and ...eightfold degenerate points that are predicted to give rise, under modest magnetic fields or strain, to topological semimetallic behaviors. The present study shows that the nonsymmorphic compound PdSb2 hosts six‐component fermions or sextuplets. Using angle‐resolved photoemission spectroscopy, crossing points formed by three twofold degenerate parabolic bands are directly observed at the corner of the Brillouin zone. The group theory analysis proves that under weak spin–orbit interaction, a band inversion occurs.
Condensed matter systems provide immense opportunity to study novel excitations which are otherwise not yet identified as independent particles. Nonmagnetic PdSb2 with pyrite‐type structure contains all the required symmetries to exhibit sixfold degenerate points. Angle‐resolved photoemission spectroscopy measurements along with first‐principles calculations provide signatures of such sextuple points below the Fermi energy in PdSb2.
Cavity magnon polaritons (CMPs) are quasiparticles that combine the advantages of high-speed photons and long-lived spins. The coupling between magnons and photons can be tuned to chiral situations ...by controlling the microwave polarization, which is important to manipulate the asymmetrical energy flow for coherent signal processing. Here, by strongly coupling a magnon mode to the microwave field with controllable polarization from a cross cavity, we realize the flexible control of CMP dynamics via the chiral coupling effect. Such control allows the cavity resonance to evolve into doublet or triplet spectra under zero-detuning condition depending on the left- and right-handed circular or linear polarization at the center of our cross cavity via the phase control technique. In addition to the experimental findings, we establish a harmonic oscillator model that can well describe our results. Furthermore, we display a functionality of nonreciprocal transmission using the chiral condition in coupling. Directional transmission is observed for all CMP triplet modes, exhibiting a significant chiral contrast in both dispersion and amplitude. Our results demonstrate that CMPs built in a cross cavity can realize tunability from microwave polarization and can function as an on-chip device with a one-way energy transfer, which has potential applications in switches, isolators, and logical gates that utilize CMP dynamics.
B7-H4 belongs to the immune costimulatory B7 family and is thought to negatively regulate T-cell mediated immunity, and may contribute an important role in tumor immune evasion. Although the ...expression of B7-H4 has been observed in human pancreatic cancer, the prognostic significance of this expression is poorly understood. This present study explored the prognostic value of B7-H4 in pancreatic cancer. Patients with pancreatic cancer and healthy controls were recruited at the Second Affiliated Hospital to Zhejiang University from January 2011 to December 2014. Expression of B7-H4 was assessed by immunohistochemistry. Immunohistochemical analysis indicated that B7-H4 was expressed in 100% (188/188) of the pancreatic cancer tumor tissue samples, while only in 68% (17/25) of normal pancreatic tissue samples. Furthermore, the expression levels of B7-H4 in pancreatic cancer patients were significantly higher than in controls (P < .01). A significant difference in B7-H4 expression was observed between patients with late tumor-node-metastasis (TNM) stage (III and IV) and early TNM stage (I and II) (P < .01). The expression of B7-H4 was associated with distant metastasis (P < .01) and differentiation (P < .01). In addition, B7-H4 expression (P < .01), distant metastasis (P < .01), TNM stage (P < .01), differentiation (P < .01) and chemotherapy treatment (P < .05) were indicators of poor overall survival time. Multivariate survival analysis indicated that B7-H4 expression, distant metastasis, and chemotherapy treatment (P < .05) were independent prognostic indicators of poor overall survival. In conclusion, B7-H4 is highly expressed in pancreatic cancer, and is an independent predictor of poor prognosis in patients with pancreatic cancer. B7-H4 may represent an immunotherapeutic target in pancreatic cancer.
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