Quantum defects in two-dimensional van der Waals materials

Quantum defects in solid materials, such as nitrogen-vacancy color centers in diamond, have been extensively studied and successfully demonstrated as single photon emitters and potential qubits for quantum computers. However, a major challenge has always been positioning these quantum defects near the sample surface for measuring or sensing purposes. The emergence of quantum defects in two-dimensional (2D) van der Waals (vdW) materials open up new opportunities for overcoming these limitations. These materials possess unique properties, including vdW interlayer coupling and clean surfaces without unsaturated dangling bonds, which provide greater advantages for manufacturing multi-qubit systems. In this review, we present the research progress on quantum defects in 2D vdW materials, covering quantum guidelines for spin defects in solid state, the latest demonstrations of quantum defects, the unique methods and techniques for generating and modulating defects in 2D vdW materials.</p

A spin–orbit scattering–enhanced high upper critical field at the LaAlO3/KTaO3(111) superconducting interface

Spin–orbit interaction is essential to enhance the in-plane upper critical field of two-dimensional superconductors. Here, we report the LaAlO _3 /KTaO _3 (111) superconducting interface ( T _c,0 ≈ 0.475 K) with a high in-plane upper critical field (∼1.6 T), which is approximately 1.8 times the Pauli paramagnetic limit. The H $-$ T superconducting phase diagram is well-fitted by the Klemm–Luther–Beasley (KLB) theory, and the relevant spin–orbit scattering (SOS) length is approximately 32 nm. Furthermore, normal-state magnetotransport measurements show signatures of weak antilocalization caused by strong spin–orbit coupling in LaAlO _3 /KTaO _3 (111). The spin diffusion length derived from magnetotransport measurements was 40 nm at 2 K, which is comparable with the SOS length. The conformity of the phase diagram with the KLB theory and the consistency of normal state spin diffusion length and superconducting SOS length indicate that the high in-plane upper critical field at the LaAlO _3 /KTaO _3 (111) superconducting interface is enhanced by SOS