Superfluid stiffness of twisted multilayer graphene superconductors
- URL: http://arxiv.org/abs/2406.13742v1
- Date: Wed, 19 Jun 2024 18:00:04 GMT
- Title: Superfluid stiffness of twisted multilayer graphene superconductors
- Authors: Abhishek Banerjee, Zeyu Hao, Mary Kreidel, Patrick Ledwith, Isabelle Phinney, Jeong Min Park, Andrew M. Zimmerman, Kenji Watanabe, Takashi Taniguchi, Robert M Westervelt, Pablo Jarillo-Herrero, Pavel A. Volkov, Ashvin Vishwanath, Kin Chung Fong, Philip Kim,
- Abstract summary: We report the measurement of $rho_s$ in magic-angle twisted trilayer graphene (TTG)
We find a linear temperature dependence of $rho_s$ at low temperatures and nonlinear Meissner effects in the current bias dependence.
Our results provide strong evidence for nodal superconductivity in TTG and put strong constraints on the mechanisms of these graphene-based superconductors.
- Score: 1.374933941124824
- License: http://creativecommons.org/licenses/by/4.0/
- Abstract: The robustness of the macroscopic quantum nature of a superconductor can be characterized by the superfluid stiffness, $\rho_s$, a quantity that describes the energy required to vary the phase of the macroscopic quantum wave function. In unconventional superconductors, such as cuprates, the low-temperature behavior of $\rho_s$ drastically differs from that of conventional superconductors due to quasiparticle excitations from gapless points (nodes) in momentum space. Intensive research on the recently discovered magic-angle twisted graphene family has revealed, in addition to superconducting states, strongly correlated electronic states associated with spontaneously broken symmetries, inviting the study of $\rho_s$ to uncover the potentially unconventional nature of its superconductivity. Here we report the measurement of $\rho_s$ in magic-angle twisted trilayer graphene (TTG), revealing unconventional nodal-gap superconductivity. Utilizing radio-frequency reflectometry techniques to measure the kinetic inductive response of superconducting TTG coupled to a microwave resonator, we find a linear temperature dependence of $\rho_s$ at low temperatures and nonlinear Meissner effects in the current bias dependence, both indicating nodal structures in the superconducting order parameter. Furthermore, the doping dependence shows a linear correlation between the zero temperature $\rho_s$ and the superconducting transition temperature $T_c$, reminiscent of Uemura's relation in cuprates, suggesting phase-coherence-limited superconductivity. Our results provide strong evidence for nodal superconductivity in TTG and put strong constraints on the mechanisms of these graphene-based superconductors.
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