Controlling unconventional superconductivity in artificially engineered f-electron Kondo superlattices

Abstract

Unconventional superconductivity and magnetism are intertwined on a microscopic level in a wide class of materials, including high-T c cuprates, iron pnictides, and heavy-fermion compounds. Interactions between superconducting electrons and bosonic fluctuations at the interface between adjacent layers in heterostructures provide a new approach to this most fundamental and hotly debated subject. We have been able to use a recent state-of-the-art molecular-beam-epitaxy technique to fabricate superlattices consisting of different heavy-fermion compounds with atomic thickness. These Kondo superlattices provide a unique opportunity to study the mutual interaction between unconventional superconductivity and magnetic order through the atomic interface. Here, we design and fabricate hybrid Kondo superlattices consisting of alternating layers of superconducting CeCoIn5 with d-wave pairing symmetry and nonmagnetic metal YbCoIn5 or antiferromagnetic heavy fermion metals such as CeRhIn5 and CeIn3. In these Kondo superlattices, superconducting heavy electrons are confined within the two-dimensional CeCoIn5 block layers and interact with neighboring nonmagnetic or magnetic layers through the interface. Superconductivity is strongly influenced by local inversion symmetry breaking at the interface in CeCoIn5/YbCoIn5 superlattices. The superconducting and antiferromagnetic states coexist in spatially separated layers in CeCoIn5/CeRhIn5 and CeCoIn5/CeIn3 superlattices, but their mutual coupling via the interface significantly modifies the superconducting and magnetic properties. The fabrication of a wide variety of hybrid superlattices paves a new way to study the relationship between unconventional superconductivity and magnetism in strongly correlated materials.

Superconducting piezoelectric effect

“…Search for the helical superconducting state with finite total momentum of Cooper pairs has been conducted in the noncentrosymmetric superconductors under a magnetic field [4,26]. Indications for the helical superconductivity have been recently obtained in several superconductors via measurements of the upper critical field [29][30][31] and nonreciprocal transport [32], and direct observation in the superconducting state is awaited. Based on the finding of a close relation between the Cooper pairs' momentum and the SCPE, we proposed the probe of the helical superconducting state using the SCPE.…”

Topological d-wave superconductivity in two dimensions

“…Some of the heavy-fermion superconductors can also be good candidates because they show d-wave superconductivity. For instance, atomicallythin layers of CeCoIn 5 have already been fabricated, and the spin-orbit coupling is controllable 98,99 . Thus, the heterostructure of CeCoIn 5 is also a good platform to realize TSC based on our scenario.…”

“…Although it is unclear that this condition is satisfied in the thin film superconductors mentioned above, α can be controlled to some extent by the gating techniques including the electric double-layer transistor [107][108][109] . Artificial superlattices of CeCoIn 5 98 are also promising, where the Rashba spin-orbit coupling can be introduced by the tricolor stacking and is tunable by the layer thickness 99,110 . These noncentrosymmetric d-wave superconductors offer a fertile ground to explore TSC.…”

“…Furthermore, recent advances in technology have provided a way to synthesize artificial 2D systems with multilayer structures. For examples, heavy-fermion superlattices [97][98][99]166,167 and van der Waals heterostructures 168 are current topics of interests. We will review a heavy fermion superlattice CeCoYb 5 /YbCoIn 5 in Sec.…”

Combined Light and Electron Scattering for Exploring Proximity Effects on Hydrogen Absorption in Vanadium

“…The physical properties of thin films are usually influenced by the presence of neighbor materials. This is often referred to as proximity effects, which are clearly seen in the onset of magnetic, superconducting and electrical properties of the thin films [1][2][3]. The changes of physical properties are usually related to the influence of electronic structuretransformation and special physical properties arising from the composition.…”