Exploring dynamics and confinement in the superconducting condensate using scanning tunnelling microscopy

Sang Hyun Joo, Jang‐Joo Kim, Jung Hoon Yoo +4 more

In pursuit of the elusive mechanism of high- T C superconductors (HTSC), spectroscopic imaging scanning tunneling microscopy (SI-STM) is an indispensable tool for surveying local properties of HTSC. Since a conventional STM utilizes metal tips, which allow the examination of only quasiparticles and not superconducting (SC) pairs, Josephson tunneling using STM has been demonstrated by many authors in the past. An atomically resolved scanning Josephson tunneling microscopy (SJTM), however, was realized only recently on Bi 2 Sr 2 CaCu 2 O 8+ x (Bi-2212) below 50 mK and on the Pb(110) surface at 20 mK. Here we report the atomically resolved SJTM on Bi 2 Sr 2 CaCu 2 O 8+ x at 4.2 K using Bi-2212 tips created in situ . The I - V characteristics show clear zero bias conductance peaks following Ambegaokar-Baratoff (AB) theory. A gap map was produced for the first time using an atomically resolved Josephson critical current map I C ( r ) and AB theory. Surprisingly, we found that this new gap map is anticorrelated to the gap map produced by a conventional method relying on the coherence peaks. Quasiparticle resonance due to a single isolated zinc atom impurity was also observed by SJTM, indicating that atomically resolved SJTM was achieved at 4.2 K. Our result provides a starting point for realizing SJTM at even higher temperatures, rendering possible investigation of the existence of SC pairs in HTSC above the T C .

P. H. Videler, N. Rando, P. Verhoeve +6 more

In this paper we investigate the QP transport and loss mechanisms in a superconducting tunnel junction using the Low Temperature Scanning Electron Microscopy (LTSEM) technique. This approach allows precise control of the energy and position of a deposited electron pulse, which, within certain conditions, simulates the X-ray photo-absorption process. An Nb-Al-AlOxNb junction designed as a test structure which included Al blocks in the leads to act as quasiparticle traps, has been investigated. Asymmetries in the LTSEM signal distribution can be qualitatively described from the device geometry. From both the spatial distribution can be qualitatively described from the device geometry. From both the spatial distribution and the time resolved measurements the diffusion length in the amorphous Nb was determined to be of the order of 8 micrometers . The LTSEM technique has demonstrated that quasiparticles produced in the leads cannot enter the tunnel barrier due to the presence of the Al traps.

Eli M. Levenson-Falk, Filip Kos, Rajamani Vijay +2 more

Rubén Seoane Souto

Boyang Ma, Michael B. Kruger

Attosecond observations of coherent electron dynamics in molecules and nanostructures can be achieved by combining conventional scanning tunneling microscopy (STM) with ultrashort femtosecond laser pulses. While experimental studies in the subcycle regime are under way, a robust strong-field theory description has remained elusive. Here we devise a model based on the strong-field approximation. Valid in all regimes, it provides a surprising analogy to the standard model of STM. We show that the intuitive three-step model of attosecond science directly emerges from our model and we also describe the optimal conditions for attosecond STM experiments.