# Zero-Bias Anomaly in a Nanowire Quantum Dot Coupled to Superconductors

 Title: Zero-Bias Anomaly in a Nanowire Quantum Dot Coupled to Superconductors Author: Lee, Eduardo J. H.; Jiang, Xiaocheng; Aguado, Ramón; Katsaros, Georgios; Lieber, Charles M.; De Franceschi, Silvano Note: Order does not necessarily reflect citation order of authors. Citation: Lee, Eduardo J. H., Xiaocheng Jiang, Ramón Aguado, Georgios Katsaros, Charles M. Lieber, and Silvano De Franceschi. 2012. Zero-bias anomaly in a nanowire quantum dot coupled to superconductors. Physical Review Letters 109(18): 186802. Full Text & Related Files: zero_bias_anomaly.pdf (8.288Mb; PDF) Abstract: We studied the low-energy states of spin-1/2 quantum dots defined in InAs/InP nanowires and coupled to aluminum superconducting leads. By varying the superconducting gap $$\Delta$$ with a magnetic field B we investigated the transition from strong coupling $$\Delta \ll T_K$$ to weak-coupling $$\Delta \gg T_K$$ , where $$T_K$$ is the Kondo temperature. Below the critical field, we observe a persisting zero-bias Kondo resonance that vanishes only for low B or higher temperatures, leaving the room to more robust subgap structures at bias voltages between $$\Delta$$ and $$2 \Delta$$. For strong and approximately symmetric tunnel couplings, a Josephson supercurrent is observed in addition to the Kondo peak. We ascribe the coexistence of a Kondo resonance and a superconducting gap to a significant density of intragap quasiparticle states, and the finite-bias subgap structures to tunneling through Shiba states. Our results, supported by numerical calculations, own relevance also in relation to tunnel-spectroscopy experiments aiming at the observation of Majorana fermions in hybrid nanostructures. Published Version: doi:10.1103/PhysRevLett.109.186802 Other Sources: http://arxiv.org/abs/1207.1259 Terms of Use: This article is made available under the terms and conditions applicable to Open Access Policy Articles, as set forth at http://nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of-use#OAP Citable link to this page: http://nrs.harvard.edu/urn-3:HUL.InstRepos:10399821 Downloads of this work: