Controlling temperature in a two-dimensional tungsten diselenide superconductor enables a transition between extended edge states and localized vortex bound states, configurations previously predicted only by theory. This was achieved by tuning the size of vortices relative to nano-ring dimensions; manipulating this scale allows control over how magnetic fluxes distribute within the superconducting material. Unexpectedly large Little Parks oscillations confirmed multiple fluxes forming a “flux necklace” arrangement upon cooling, revealing this shift from extended to localized states.
Carefully controlling temperature in a two-dimensional material switches between different arrangements of magnetic fields inside a superconductor; these configurations involve either flows around edges or trapped cores. Altering how large individual units of magnetism are compared with the size of rings within the superconducting device achieves this manipulation. This manipulation hinges on carefully adjusting how large individual units of magnetism are compared with the size of rings fabricated into the superconducting device.
A key concept is coherence length, which defines the distance superconductivity can be maintained without losing its special properties. Unexpectedly large rhythmic changes in electrical resistance confirmed multiple fluxes arranging themselves like beads on a string upon cooling, revealing a shift from flowing edge states to localised magnetic fields. Researchers at National Laboratory of Solid State Microstructures and Collaborative Innovation Centre of Advanced Quantum Science Centre of Guangdong-Hong Kong-Macao Greater Bay Area seek to understand if these findings pave the way for manipulating flux towards advanced quantum computing applications.
Flux Necklace Formation Enables Enhanced Superconducting Oscillations
Little Parks oscillations increased unexpectedly to periods as high as 70mT; previously, such large signals were unattainable due to limitations in controlling vortex distribution within superconducting rings. A shift occurred between conventional flux bundles, where magnetic fields concentrate at ring centres, and an unprecedented “flux necklace” arrangement distributing multiple fluxes along the annulus walls of nano-rings fabricated from 2M-WS2.
Tuning temperature and manipulating coherence length relative to ring width enabled this control over magnetism inside the superconductor. Ginzburg-Landau simulations confirmed that strong flux pinning energies are key for stabilising this new configuration, opening avenues towards advanced quantum computing applications reliant on precise manipulation of these quantized magnetic units.
Within nano-rings made of 2M-WS2 material, Little Parks oscillations reached periods as large as 70mT; signals above approximately 25mT were previously unattainable due to limitations controlling magnetism within superconductors. Scanning electron microscopy confirmed ring dimensions around 478nm, aligning with expected behaviour when magnetic fields concentrated at their centres, consistent with edge states residing on inner and outer rims. Cooling the device below 4.4K increased oscillation period alongside evidence that multiple fluxes distributed along annulus walls forming a “flux necklace” configuration instead of central bundles, linked to changes in coherence length relative to ring width.
Amplitude values reached up to 0.57Ω, exceeding predictions from conventional flux bundle models, demonstrating how vortex size relates to annulus width within this material.
The results demonstrate control over transitions between edge states and localized vortex bound states in two-dimensional materials; however, braiding has not yet been demonstrated. Altered magnetic behaviour is successful but sustaining coherence for quantum computation remains an open challenge while other approaches explore different materials offering stronger topological protection, avoiding precise temperature adjustments.
These alternatives sometimes lack the demonstrable control of flux distribution observed with tungsten diselenide rings. Magnetism can be controlled at a nanoscale level even though sustained coherence remains elusive in this setup. Switching between extended edge states and localised vortex bound states represents a step towards manipulating ‘flux quanta’, fundamental units used in quantum computing concepts. By tuning the relative scale of vortex size to annulus width, these tungsten diselenide rings offer that nanoscale control over magnetism.
This research demonstrated a method to move between topological edge states and localized vortex bound states using nano-rings fabricated from 2M-WS2 material. By tuning temperature, specifically cooling below 4.4K, researchers altered the coherence length relative to ring width, successfully changing how magnetic fluxes distribute within the device. This control over magnetism at the nanoscale is important because manipulating these ‘flux quanta’ is central to concepts in quantum computing. Simulations confirmed that achieving this transition requires specific values for Ginzburg-Landau parameter and flux-pinning energy, offering insights into strategies for future work on flux braiding.
👉 More information
🗞 Majorana Edge-to-bound State Transition in Interferometric Superconductor Rings
✍️ Xiangyu Bi, Aoshen Yang, Hongzi Cao, Ganyu Chen, Qizheng Sun, Junwei Huang, Da Wang, Fuqiang Huang, Qianghua Wang and Hongtao Yuan (National Laboratory of Solid State Microstructures and Collaborative Innovation Center of Advanced); Yuqiang Fang (NIST); Zeya Li (Quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area); Toshiya Ideue (The University of Tokyo); Yoshihiro Iwasa (RIKEN)
🧠 ArXiv: https://arxiv.org/abs/2610.32767
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