Bulletin of the American Physical Society
2023 APS March Meeting
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session F25: Superconductivity:JJ-I
8:00 AM–11:00 AM,
Tuesday, March 7, 2023
Room: Room 217/218
Sponsoring
Unit:
DCMP
Chair: Kush Saha, National Institute of Science Education and Research (NISER)
Abstract: F25.00007 : Topological phase transition by a tuning of superconducting phase in multi-terminal Josephson junctions*
9:12 AM–9:24 AM
Presenter:
Tomohiro Yokoyama
(Osaka University)
Authors:
Tomohiro Yokoyama
(Osaka University)
Kento Takemura
(Osaka University)
$N$ superconductors can define $N-1$ independent superconducting phase differences.
The spectrum of Andreev bound states (ABSs) in the junction is $2pi$ periodic in
all the phase differences ${ varphi }$ and can be regarded as the ``band structure.''
In a previous studies, we have demonstrated presence of topologically protected singularities (Weyl points) at zero energy.
footnote{T. Yokoyama and Yu. V. Nazarov, PRB {f 92}, 155437 (2015).}
In this study, we investigate trajectories of Weyl points when the QPC voltages and the fifth superconducting phase are tuned.
Owing to the topological protection, the Weyl points do not disappear solely.
Hence parameter modulations cause the trajectories of Weyl points connecting
the pair annihilation and creation positions in ${ varphi }$-space.
Such pair annihilation and creation coincide with the topological phase transitions between four, two, and no topological charges.
Moreover, the trajectories show two categories:
One is closed type in the first ``Brillouin zone'' and the other is open type for the annihilation and creation with neighboring ``Brillouin zone.''
We consider a phase diagram for the four- and five-terminal junctions and propose a classification of topology by the trajectories.
*T.Y. is supported by JSPS KAKENHI 18K13484
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