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SUMMARY:Topological superconductivity and Majorana zero modes in helical l
 iquids:  interactions\, phonons\, and disorder\, Dr. Chen-Hsuan Hsu [徐
 晨軒]\, IoP Academia Sinica
DTSTART:20260317T030000Z
DTEND:20260317T050000Z
DTSTAMP:20260420T133100Z
UID:indico-event-179@indico.phys.nthu.edu.tw
DESCRIPTION:Recent observations of the quantum spin Hall effect in transit
 ion metal dichalcogenide bilayer systems [1] provide a new material platfo
 rm for helical liquids on their edges [2]. These correlated one-dimensiona
 l channels with spin–momentum locking enable topological superconductivi
 ty through the proximity effect [3-5]. In this talk\, I discuss interactio
 n-\, phonon-\,and disorder-driven topological phase transitions in helical
  liquids\, focusing on a proximitized double helical liquid composed of tw
 o parallel helical channels with both local and nonlocal superconducting p
 airings. In the first part\, I show that Coulomb interactions and electron
 –phonon coupling can renormalize the effective pairing strength and ther
 eby drive transitions between topological and trivial superconducting phas
 es [6]. Within a nonperturbative framework\, we demonstrate that phonon-in
 duced renormalization can substantially modify the superconducting gap and
  suppress topological zero modes. These results highlight that interaction
 s and phonons\, which are ubiquitous in real materials\, can serve as impo
 rtant tuning knobs for topological phase transitions in helical systems. I
 n the second part\, we incorporate experimentally relevant imperfections\,
  including pairing asymmetry\, Coulomb-interaction imbalance\, and random 
 spin-flip backscattering arising from magnetic disorder or from coexisting
  charge disorder and magnetic fields [7]. Using bosonization and renormali
 zation-group analysis\, we determine how interactions\, superconducting pa
 iring\, and disorder compete to shape the transport and topological proper
 ties. We derive an analytic expression for the number of zero modes in ter
 ms of renormalized couplings\, revealing a topological Z invariant in cont
 rast to the Z2 invariant in the clean limit. Spin-flip backscattering lift
 s the degeneracy of the zero-mode conditions and drives asymmetry-class tr
 ansition from DIII to BDI\, enabling a phase hosting a single Majorana zer
 o mode per corner. Our findings demonstrate that disorder and channel asym
 metry can induce or revive Majorana zero modes and generate cascades of to
 pological transitions tunable through interaction strength.These results e
 stablish imperfect helical liquids as a realistic and versatile platform f
 or electrically tunable topological superconductivity. References:[1] K. 
 Kang et al.\, Nature 628\, 522 (2024)\; K. Kang et al.\, Nano Lett. 24\, 1
 4901 (2024).[2] C.-H. Hsu et al.\, J. Phys. Mater. 9\, 011001 (2026)\; inv
 ited Perspective.[3] C.-H. Hsu et al.\, Semicond. Sci. Technol. 36\, 12300
 3 (2021)\; topical review.[4] J. Klinovaja et al.\, Phys. Rev. B 90\, 1554
 47 (2014).[5] C.-H. Hsu et al.\, Phys. Rev. Lett. 121\, 196801 (2018).[6] 
 C.-H. Hsu\, Nanoscale Horiz. 9\, 1725 (2024)\; highlighted on the journal 
 cover.[7] A. Ohorodnyk and C.-H. Hsu\, arXiv:2512.10335 (2025).\n\nhttps:/
 /indico.phys.nthu.edu.tw/event/179/
LOCATION:Physics/620
URL:https://indico.phys.nthu.edu.tw/event/179/
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