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  • Letter
  • Open Access

Topological superfluid responses of superconducting Dirac semimetals

Jun-Ang Wang1,2,*, Mohamed Assili1,†, and Panagiotis Kotetes1,‡

  • *wangjunang@itp.ac.cn
  • †m.assili@itp.ac.cn
  • ‡kotetes@itp.ac.cn
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Phys. Rev. Research 6, L022053 – Published 6 June, 2024

DOI: https://doi.org/10.1103/PhysRevResearch.6.L022053

Abstract

We demonstrate that topological constraints do not only dictate the geometric part of the superfluid stiffness, but can also govern the total superfluid stiffness. By introducing a general adiabatic approach for superfluid responses, we showcase such a possibility by proving that the stiffness of a superconducting Dirac cone in two dimensions (2D) is proportional to its topological charge. By relying on the emergent Lorentz invariance of Dirac electrons, we unify the superfluid stiffness and quantum capacitance in these systems. Based on this connection, we further predict a topological origin for the quantum capacitance of a Josephson junction where 2D massless Dirac electrons are sandwiched between two conventional superconductors. We show that the topological responses persist upon effecting strain, are resilient against weak disorder, and can be experimentally controlled via a Zeeman field. Remarkably, the nonuniversal topological quantization of the two superfluid responses, yet implies the universal topological quantization of the admittance modulus of the superconducting Dirac system in units of conductance. The quantum admittance effect arises when embedding the superconducting Dirac system in an ac electrical circuit with a frequency tuned at the absorption edge. These findings are in principle experimentally observable in graphene-superconductor hybrids.

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Superfluid stiffness and Josephson quantum capacitance: Adiabatic approach and topological effects

Jun-Ang Wang, Mohamed Assili, and Panagiotis Kotetes
Phys. Rev. Research 6, 023256 (2024)

Article Text

Supplemental Material

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Outline

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Phys. Rev. Research 6, L022053– Published 6 June, 2024
  • Received 1 December 2022
  • Revised 8 November 2023
  • Accepted 18 May 2024
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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