Chiral d -wave superconductivity in a triangular surface lattice mediated by long-range interaction

Abstract

Correlated ad-atom systems on the Si(111) surface have recently attracted an increased attention as strongly correlated systems with a rich phase diagram. We study these materials by a single band model on the triangular lattice including 1/r long-range interaction. Employing the recently proposed TRILEX method we find an unconventional superconducting phase of chiral d-wave symmetry in hole-doped systems. The superconductivity is driven simultaneously by both charge and spin fluctuations and is strongly enhanced by the long-range tail of the interaction. We provide an analysis of the relevant collective bosonic modes and explain how in triangular symmetry both charge and spin channels contribute to the Cooper pairing.

Triplet Superconductivity from Nonlocal Coulomb Repulsion in an Atomic Sn Layer Deposited onto a Si(111) Substrate

“…Another group-IV adsorbate, which features essentially the same bandstructure as Sn/Si(111) and is also believed to have significant non-local Coulomb interactions, is Pb/Si(111) [29,30,39]; it was estimated that U 1 U 0 = 3 5 and, according to Fig. 2 (a), we find the same pairing instabilities as for Sn/Si(111).…”

“…By applying the weak-coupling renormalization group (WCRG) method, we are able to find the leading superconducting instabilities in an analytically controlled way in the limit of weak interactions. While correlated electrons on a hexagonal lattice have a generic propensity towards chiral d-wave pairing [36][37][38][39][40][41][42][43], we find that the FS structure of Sn/Si(111) leads to a competition between singlet and triplet pairing channels. The inclusion of nonlocal Coulomb interactions strongly suppresses the chiral d-wave state, and instead favors f -wave and chiral p-wave triplet pairing.…”

“…2 (c) and reveals the aforementioned competition between the different pairing channels. This competition between odd-(f -and p-wave) and even-parity pairing (d-wave) is a priori unexpected as most often chiral d-wave is the leading instability for hexagonal tight-binding models [39][40][41][42][43]. For comparison, in Fig.…”

Superconductivity in a Hole-Doped Mott-Insulating Triangular Adatom Layer on a Silicon Surface

“…As we will show, its presence suggests the possibility of a phonon-mediated superconducting state due to an interfacial coupling with the Si substrate; however, the strong correlations in the Sn film likely suppress such a conventional mechanism. Interestingly, the geometrical frustration of the triangular lattice and strong correlations can produce a chiral 𝑑 + i𝑑 superconducting order parameter that breaks time-reversal symmetry giving rise to interesting edge modes [8][9][10][11] .…”

Real-space cluster dynamical mean-field theory: Center-focused extrapolation on the one- and two particle-levels

“…Finally, CDMFT calculations and the CFE extrapolation can be carried out to temperatures currently inaccessible to exact diagrammatic Monte Carlo techniques, making the CDMFT+CFE procedure a powerful computational tool to access the physics of nonlocal correlations beyond dynamical mean-field theory. The presented algorithmic advancements may be applied to improve material-realistic studies of correlated electron systems such as transition metal oxides [75], molecular materials like the family of organic superconductors [76], and correlated ad-atoms on semiconductor surfaces [77][78][79][80]. Within practical restrictions, i.e., an upper limit for local (spin-orbital) plus cluster degrees of freedom, CDMFT+CFE can help to explore regimes in the phase diagram which are beyond the local limit such as second order phase transitions (e.g., magnetic ordering or superconducting pairing).…”