Superconducting Proximity Effect in d‐Wave Cuprate/Graphene Heterostructures

Abstract

Superconducting proximity effects in graphene have received a great deal of attention for over a decade now. This has unveiled a plethora of exotic effects linked to the specificities of graphene's electronic properties. The vast majority of the related studies are based on conventional, low-temperature superconducting metals with isotropic s-wave pairing. Here recent advances made on the less studied case of unconventional high-temperature superconducting cuprates are reviewed. These are characterized by an anisotropic d-wave pairing, whose interplay with Dirac electrons yields very rich physics and novel proximity behaviors. A theoretical analysis is provided and the experiments reported so far are summarized. These unveil hints of proximity-induced unconventional pairing and demonstrate the gate-tunable, long-range propagation of high-temperature superconducting correlations in graphene. Finally, the fundamental and technological opportunities brought by the theoretical and experimental advances are discussed, together with the interest in extending similar studies to other Dirac materials.

Transport signatures of Bogoliubov Fermi surfaces in normal metal/time-reversal symmetry broken d-wave superconductor junctions

“…For any value of α between 0 and π/4 (0 < α ⩽ π/4), ABSs are formed at the interface due to unconventional nature of pairing potential. It is already established as a signature of the anisotropy in the literature [63,64]. Interestingly, the ZBC peak is splitted and moves towards the higher eV with increasing B as shown in figure 3(b).…”

“…For the sake of completeness and better understanding, we start with the results in the absence of any Zeeman field, which is already established in the literature [63,64]. In figure 2(a), we show the normalized differential conductance G/G N as a function of eV for α = 0 and no magnetic field is applied.…”

Andreev Reflection and Klein Tunneling in High-Temperature Superconductor-Graphene Junctions

“…Therefore, the superconducting Gr Δ region is connected to a p-n junction formed in the Gr 0 -Gr regions by a gate. Modulation of the gate results in an asymmetric conductance, as the doping in the Gr 0 -Gr regions changes from p þ -p to p-n as we show below, beyond what was previously reported in YBCO-graphene junctions [28][29][30].…”

Photoinduced spin-polarized transport and controllable valley-triplet pairing states in a silicene-superconductor junction

“…That is, generally, an electron incoming from the NM side with energy below the superconducting energy gap ∆ 0 (ε < ∆ 0 ) can not enter the superconductor, but it is reflected as a hole backwards at the interface with a Cooper pair being transferred into in the SC lead. Experimentally, AR can be characterized based on the finite subgap conductance of the NM-SC interface and the subgap conductance spectrum may offer an opportunity to test the physical properties of superconductivity in materials by scanning tunneling microscopy [2][3][4]. In addition, it can be also used to measure the spin and valley polarizations of a material by a superconducting contact [5,6].…”