Two-dimensional (2D) superconductors, characterized by inherent quantum confinement, strong spin-orbit coupling, and diverse forms of symmetry breaking, provide an ideal platform for exploring novel quantum transport phenomena. This review summarizes recent experimental progress on the non-reciprocal properties of 2D superconductors, focusing on the second harmonic resistance (SHR) in the resistive superconducting state and the supercurrent diode effect (SDE) in the dissipationless superconducting regime. We discuss the various origins of these phenomena, distinguishing between intrinsic mechanisms, such as finite-momentum Cooper pairing, and extrinsic mechanisms driven by asymmetric vortex dynamics and device geometry. We present a systematic classification of zero-field SDE into polarity-reversed and polarity-locked behaviors, a distinction governed by the interplay between intrinsic time-reversal symmetry breaking and the external magnetic response. Furthermore, we examine how the efficiency and polarity of the SDE are modulated by tuning parameters including magnetic/electric fields, strain, device geometry, thermodynamic conditions, and microwave irradiation. We conclude by highlighting the application potential of these tunable diodes in high-efficiency rectification, superconducting logic, and neuromorphic computing.

Two-dimensional superconductivity has become a major frontier in condensed matter physics. It holds the key to understanding the mechanism of high-temperature superconductors and offers an exceptional arena for stabilizing emergent quantum states enabled by enhanced electron correlations in reduced dimensionality. These states are frequently characterized by spatial modulations and intertwined with competing orders, calling for studies that combine real-space imaging with local spectroscopy. Scanning tunneling microscopy and spectroscopy meet this need by directly accessing the local density of states with lattice-scale resolution. In this review, we summarize recent advances in the study of several representative unconventional superconductors using this technique, focusing on the direct characterization of high-temperature superconducting planes, pair-density waves, and topological superconductivity in both artificial heterostructures and intrinsic materials. We conclude by outlining current challenges and future directions motivated by these microscopic insights.

Two-dimensional (2D) superconductors provide a powerful building block for engineering emergent quantum states shaped by reduced dimensionality, enhanced quantum fluctuations, and interfacial symmetry breaking. In van der Waals (vdW) heterostructures, atomically sharp and lattice-mismatch-free interfaces enable superconductivity to be deliberately coupled with magnetism, spin-orbit interaction, and band topology, allowing collective electronic orders to be combined and reconfigured in ways unattainable in bulk materials. This review summarizes recent advances in vdW heterostructures of 2D superconductors, focusing on superconductor/magnet (S/M), superconductor/topological material (S/T), and superconductor/superconductor (S/S) junctions. We discuss the microscopic mechanisms underlying proximity effects and highlight how interfacial exchange fields, spin-orbit coupling, and twist-controlled tunneling give rise to unconventional pairing, long-range spin-triplet supercurrents, nonreciprocal Josephson transport, and topological superconductivity potentially hosting Majorana bound states. Beyond their fundamental significance, the ability to controllably generate topological and nonreciprocal superconducting states positions 2D superconductor heterostructures as promising building blocks for emerging quantum technologies, including ultra-sensitive quantum sensing, programmable superconducting logic, and energy-efficient quantum and neuromorphic computing architectures. Looking forward, advances in materials synthesis, interface engineering, and device integration are expected to further expand the scope and functionality of 2D superconductor heterostructures, reinforcing their role as a central platform for exploring and controlling emergent quantum phases

The interplay of superconductivity with non-trivial magnetic textures is a promising route toward the engineering of topological superconductivity and Majorana quasiparticles. In this paper, we demonstrate the realization of topological superconductivity in a d-wave superconductor coupled to a skyrmion lattice. Transitions between different topological phases can be induced by tuning the chemical potential and the magnetic exchange coupling. For intermediate-coupling strength, we unveil the formation of Chern bands of conduction electrons coupled to the magnetic skyrmions and present the emergence of an effective chiral p-wave pairing induced in the non-trivial Chern band. Majorana zero modes localized at the cores of the superconducting vortex lattice are revealed for topological superconducting phases with odd superconducting Chern numbers.

Majorana surface states in time-reversal invariant (TRI) topological superconductors (TSCs) typically exhibit a highly anisotropic magnetic response, a phenomenon termed "Majorana Ising spins." This Ising character is governed by the crystalline symmetries protecting the topological phase. In this work, we investigate the orientation and tunability of Majorana Ising spins within TRI TSCs engineered in two-dimensional spin-orbit coupled systems proximitized to an extended s-wave superconductor. We demonstrate that the interplay between Rashba and Dresselhaus spin-orbit couplings (SOC) plays a decisive role in determining the Ising spin orientation. In the limit of pure Rashba SOC, the Ising spin aligns along the $x$-axis, protected by mirror symmetry $M_x$, whereas for pure Dresselhaus SOC, it orients along the $y$-axis, protected by the rotational symmetry $C_{2y}$. Crucially, we reveal that when both Rashba and Dresselhaus interactions coexist, the Ising spin direction becomes continuously tunable within the basal plane. By adjusting the relative strengths of the SOC parameters — experimentally accessible via gating in semiconductor heterostructures — any orientation between the $x$- and $y$ axes can be achieved. We validate these findings by calculating the topological winding number $W$ and elucidating the symmetry-protection mechanism for the tunable phases. Our results propose a pathway for manipulating Majorana fermions in quantum devices through purely electrical means, bridging the gap between symmetry-protected topology and functional spintronic applications.