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Current-induced magnetization hysteresis defines atom trapping in a superconducting atomchip

by Fritz Diorico, Stefan Minniberger, Thomas Weigner, Benedikt Gerstenecker, Naz Shokrani, Zaneta Kurpias, Jorg Schmiedmayer

Submission summary

As Contributors: Fritz Diorico · Jörg Schmiedmayer
Arxiv Link: https://arxiv.org/abs/1803.08115v3
Date accepted: 2018-06-02
Date submitted: 2018-05-29
Submitted by: Diorico, Fritz
Submitted to: SciPost Physics
Discipline: Physics
Subject area: Quantum Physics
Approach: Experimental

Abstract

The physics of superconducting films, and especially the role of remnant magnetization has a defining influence on the magnetic fields used to hold and manipulate atoms on superconducting atomchips. We magnetically trap ultracold ^{87}Rb atoms on a 200{\mu}m wide and 500nm thick cryogenically cooled niobium Z wire structure. By measuring the distance of the atomcloud to the trapping wire for different transport currents and bias fields, we probe the trapping characteristics of the niobium superconducting structure. At distances closer than the trapping wire width, we observe a different behaviour than that of normal conducting wire traps. Furthermore, we measure a stable magnetic trap at zero transport current. These observations point to the presence of a remnant magnetization in our niobium film which is induced by a transport current. This current-induced magnetization defines the trap close to the chip surface. Our measurements agree very well with an analytic prediction based on the critical state model (CSM). Our results provide a new tool to control atom trapping on superconducting atomchips by designing the current distribution through its current history.

Current status:

Ontology / Topics

See full Ontology or Topics database.

Atom chips Critical state model (CSM) Hysteresis Magnetic traps Niobium (Nb) Rubidium (Rb) Superconducting films Traps, trapping potentials Ultracold atoms

List of changes

Summary of changes:
1) We have modified figure 1 for better clarify as per referee suggestion.
2) Figure 3 and its caption have been reformatted in order to better understand the experimental sequences and as well as the magnetic field history of the atomchip. The magnetic field history was also recalculated since there was an error in the original plot.
3) We have made changes to section 4.2 to include the referee queries. We believe these will be useful to the readers. We have added a few paragraphs after the first original paragraph to explain the history of the experienced currents and fields of the niobium atomchip which was not explained in the original submission. In connection to this, a short sentenced is also added in figure 2 mentioning this briefly. We rewrote paragraph 4 on the original submission to include the suggested reference by referee 2. We have also rewritten the last paragraph to better explain the zero current trap.
4) We added reference [42] in paragraph 3 of section 3 which is in connection to the referee 2’s query.
5) We added a sentence in the conclusion and outlook section to highlight the overall effect of the current-induced magnetization to how the wire behaves.
6) We have made the typographical errors pointed out by the referees throughout the text and have adapted the term “remanence” as suggested

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