Two-dimensional (2D) superconducting systems are of great importance for exploring exotic quantum physics. The recent development of fabrication techniques has stimulated studies of high-quality singlecrystalline 2D superconductors, where intrinsic properties give rise to unprecedented physical phenomena. Here, we report the observation of Zeeman-type spin-orbit interaction protected superconductivity (Zeeman-protected superconductivity) in 4-monolayer (ML) to 6-ML crystalline Pb films grown on striped incommensurate Pb layers on Si(111) substrates by molecular beam epitaxy. An anomalously large in-plane critical field far beyond the Pauli limit is detected, which can be attributed to the Zeeman-protected superconductivity due to the in-plane inversion symmetry breaking at the interface. Our work demonstrates that, in superconducting heterostructures, the interface can induce Zeeman-type spin-orbit interactions and modulate the superconductivity.

Monolayer NbSe2 has recently been shown to be a 2-dimensional superconductor, with a competing charge-density wave (CDW) order. This work investigates the electronic structure of monolayer NbSe2 based on first principles calculations, focusing on charge and magnetic orders in connection to the superconductivity. It is found that decreased screening in the monolayer NbSe2 with a perfect lattice exhibits magnetic instability, which is removed by the formation of CDW. Two energetically competitive but distinct 3×3 CDW structures are revealed computationally, which have a significant impact on the Fermi surface. The relations of the potential CDW phases with experimental structure and the coexisting superconductivity are discussed.Layered transition metal dichalcogenides (TMDCs) MX 2 , where M is a transition metal and X is a chalcogen, are a remarkable class of materials displaying a multitude of correlation effects, ranging from CDW, magnetic ordering to superconductivity. In recent years, TMDCs have become available in monolayer forms [1][2][3][4][5]. In particular, monolayer niobium diselenide, NbSe 2 , has an extraordinarily rich phase diagram with respect to temperature. In the bulk form, NbSe 2 is one of the first materials found to host coexisting CDW and superconducting orders [6, 7]. In the monolayer limit, superconductivity again coexists with the CDW order, with a superconducting T c = 1.9 K [8] compared with the bulk value 7 K. A commensurate charge-density wave (CDW) transition was found at 145 K [1], with CDW vector q = 1 3 a * , corresponding to a structural reconstruction within a 3×3 supercell. In the monolayer limit, on the other hand, it is well known that screening is significantly reduced compared to the bulk counterpart, leading sometimes to dramatically enhanced electronic correlation. Indeed, previous first principles calculations suggest possible antiferromagnetic order in monolayer NbSe 2 in the absence of CDW order [9, 10]. The above observations indicate that the correlations arising from lattice and interaction are both important in monolayer NbSe 2 .On account of such multi-correlated nature, the interplay of different correlation effects, and therefore possible phases of monolayer NbSe 2 , are yet to be clarified, which requires treating different instabilities on the same footing. One aim of the present paper, therefore, is to analyze the equilibrium atom arrangement in the CDW phase of monolayer NbSe 2 , and at the same time, the competition between the CDW and magnetic instabilities. It is revealed that the formation of CDW phase eventually suppresses the magnetic instability, providing clarification to the vagary regarding the absence of magnetic order in monolayer NbSe 2 . A second objective of this paper is to understand the electronic structure of monolayer NbSe 2 , in the eventual low-temperature CDW phase. A Brillouin zone unfolding scheme is devised to compare the Fermi surface of the CDW phase to that of the symmetric lattice phase. Whereas the monolayer NbSe 2 with symmetr...

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A bilayer chiral metamaterial (CMM) is proposed and demonstrated to exhibit triple-band asymmetric transmission (AT) of linear polarization when the electromagnetic waves propagate in two opposite directions. Simulated and measured results show that the proposed bilayer CMM can rigorously satisfy the AT theorem and can achieve cross-polarization conversion with high efficiencies for both x-and y-polarized waves. Further simulations reveal that the resonant frequencies can be adjusted by scaling the unit cell, which indicate its wide applications in practice.