Coupled Yu–Shiba–Rusinov States in Molecular Dimers on NbSe₂

Abstract

Magnetic impurities have a dramatic effect on superconductivity by breaking the time-reversal symmetry and inducing so-called Yu–Shiba–Rusinov (YSR) low energy bound states within the superconducting gap. The spatial extent of YSR states is greatly enhanced in two-dimensional (2D) systems, which should facilitate the formation of coupled states. Here, we observe YSR states on single cobalt phthalocyanine (CoPC) molecules on a 2D superconductor NbSe2 using low-temperature scanning tunneling microscopy (STM) and spectroscopy. We use STM lateral manipulation to create controlled CoPc dimers and demonstrate the formation of coupled YSR states. The experimental results are corroborated by theoretical analysis of the coupled states in lattice and continuum models.

Electron and Cooper-pair transport across a single magnetic molecule explored with a scanning tunneling microscope

“…Moreover, in the seminal experimental work on the competition between Cooper pairing and Kondo screening [21], it was further demonstrated that an increased exchange coupling between the magnetic impurity and the superconductor leads to a decrease of |ε B | and a crossing of ε B with the Fermi level accompanied by the inversion of the electron-hole spectral weight. Several other works followed presenting the requirement of topological Shiba bands for the observation of Majorana modes in atomic chains [22], the impact of magnetic anisotropy on YSR states [23], the influence of the dimensionality of the superconductor on the spatial coherence of the bound states [24], a detailed understanding of the orbital origin of YSR multiplets [25,26], the occurrence of YSR states in proximity-induced superconductor-molecule junctions [27], the spin polarization of YSR states [28], and coupling phenomena [29].…”

Spin-Resolved Spectroscopy of the Yu-Shiba-Rusinov States of Individual Atoms

“…DOI: 10.1103/PhysRevLett.119.197002 Recent investigations of chains [1][2][3] and arrays [4,5] of magnetic atoms in contact with surfaces of s-wave superconductors in view of Majorana zero modes and topological superconductivity triggered renewed interest in the properties of the basic constituent of such systems, the individual magnetic adatom. Typically, such adatoms induce quasiparticle excitations inside the superconducting energy gap [6][7][8], referred to as Yu-Shiba-Rusinov (YSR) states, which hamper the identification of topologically nontrivial edge states [3,9], calling for a thorough characterization of all experimentally accessible properties of YSR states.Following the first experimental verification of YSR states of individual atoms using scanning tunneling spectroscopy (STS) [10], there were numerous experimental studies, focusing on orbital effects [11][12][13], magnetic anisotropy [14], effects of reduced dimensionality of the superconductor [15], effects of coupling [11,16], and the competition between Kondo screening and superconducting pairing [17,18]. However, the investigation of the spin polarization of the YSR state of individual atoms, which could serve as a fingerprint for the distinction from topological states [19], was so far restricted to theoretical predictions [6][7][8][20][21][22].…”

“…Following the first experimental verification of YSR states of individual atoms using scanning tunneling spectroscopy (STS) [10], there were numerous experimental studies, focusing on orbital effects [11][12][13], magnetic anisotropy [14], effects of reduced dimensionality of the superconductor [15], effects of coupling [11,16], and the competition between Kondo screening and superconducting pairing [17,18]. However, the investigation of the spin polarization of the YSR state of individual atoms, which could serve as a fingerprint for the distinction from topological states [19], was so far restricted to theoretical predictions [6][7][8][20][21][22].…”

Emergent quantum matter in graphene nanoribbons

“…In the case of graphene nanoribbons the behavior is more complex due to the existence of several YSR branches that give rise a to a continuum of in-gap excitations. [82][83][84][85][86] FIG. 9.…”