Ising superconductivity in bulk materials

Low-dimensional materials can display exceptional characteristics that diverge significantly from their larger-scale counterparts. For example, a single layer of NbSe₂ demonstrates Ising superconductivity, with its in-plane upper critical field surpassing the Pauli limit, a phenomenon absent in the bulk NbSe₂. However, it's worth noting that low-dimensional materials often suffer from instability and limited practicality in real-world applications. Through a series of experiments utilizing various techniques, we have discovered that bulk layered heterostructures composed of NbSe₂ mono- and bilayers sandwiched in-between spacer monolayers exhibit a two-dimensional band structure akin to a heavily doped NbSe₂ monolayer [1]. Notably, their in-plane upper critical fields exceed the Pauli limit by a factor of up to ten [2]. By combining first-principles calculations with experimental evidence, we have successfully derived precise band structure parameters, including the values for reduced interlayer coupling and significant spin-orbit splitting [3]. This quantitative analysis has provided us with insight into the fundamental underpinnings of Ising spin-orbit coupling in bulk superconductors.