Superfluid Stiffness and Flat-Band Superconductivity in Magic-Angle Graphene Probed by cQED

• URL: http://arxiv.org/abs/2406.13740v2
• Date: Thu, 31 Oct 2024 03:37:37 GMT
• Title: Superfluid Stiffness and Flat-Band Superconductivity in Magic-Angle Graphene Probed by cQED
• Authors: Miuko Tanaka, Joel Î-j. Wang, Thao H. Dinh, Daniel Rodan-Legrain, Sameia Zaman, Max Hays, Bharath Kannan, Aziza Almanakly, David K. Kim, Bethany M. Niedzielski, Kyle Serniak, Mollie E. Schwartz, Kenji Watanabe, Takashi Taniguchi, Jeffrey A. Grover, Terry P. Orlando, Simon Gustavsson, Pablo Jarillo-Herrero, William D. Oliver,
• Abstract summary: Superconductivity in magic-angle twisted bilayer graphene (MATBG) is a topic of keen interest in moir'e systems research. We use DC-transport and microwave circuit quantum electrodynamics to measure directly the superfluid stiffness of MATBG. Our findings indicate that MATBG is an unconventional superconductor with an anisotropic gap and strongly suggest a connection between quantum geometry, superfluid stiffness, and unconventional superconductivity.
• Score: 0.32018750515900324
• License:
• Abstract: The physics of superconductivity in magic-angle twisted bilayer graphene (MATBG) is a topic of keen interest in moir\'e systems research, and it may provide insight into the pairing mechanism of other strongly correlated materials such as high-$T_{\mathrm{c}}$ superconductors. Here, we use DC-transport and microwave circuit quantum electrodynamics (cQED) to measure directly the superfluid stiffness of superconducting MATBG via its kinetic inductance. We find the superfluid stiffness to be much larger than expected from conventional Fermi liquid theory; rather, it is comparable to theoretical predictions involving quantum geometric effects that are dominant at the magic angle. The temperature dependence of the superfluid stiffness follows a power-law, which contraindicates an isotropic BCS model; instead, the extracted power-law exponents indicate an anisotropic superconducting gap, whether interpreted within the Fermi liquid framework or by considering quantum geometry of flat-band superconductivity. Moreover, a quadratic dependence of the superfluid stiffness on both DC and microwave current is observed, which is consistent with Ginzburg-Landau theory. Taken together, our findings indicate that MATBG is an unconventional superconductor with an anisotropic gap and strongly suggest a connection between quantum geometry, superfluid stiffness, and unconventional superconductivity in MATBG. The combined DC-microwave measurement platform used here is applicable to the investigation of other atomically thin superconductors.

Related papers

• Measuring kinetic inductance and superfluid stiffness of two-dimensional superconductors using high-quality transmission-line resonators [1.9343861862849647]
  We demonstrate a new technique that employs high-quality-factor superconducting resonators to measure the kinetic inductance. We analyze the equivalent circuit model to extract the kinetic inductance, super stiffness, penetration depth, and ratio of imaginary and real parts of the complex conductivity. Our method will be useful for practitioners in the growing fields of superconducting physics, materials science, and quantum sensing.
  arXiv  Detail & Related papers  (2024-07-13T15:26:00Z)
• Superfluid stiffness of twisted multilayer graphene superconductors [1.374933941124824]
  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.
  arXiv  Detail & Related papers  (2024-06-19T18:00:04Z)
• Superconductivity in a Topological Lattice Model with Strong Repulsion [1.1608869880392607]
  We introduce a minimal 2D lattice model that incorporates time-reversal symmetry, band topology, and strong repulsive interactions. We demonstrate that it is formed from the weak pairing of holes atop the QSH insulator. Motivated by this, we elucidate structural similarities and differences between our model and those of TBG in its chiral limit.
  arXiv  Detail & Related papers  (2023-08-21T18:00:01Z)
• Fragmented superconductivity in the Hubbard model as solitons in Ginzburg-Landau theory [58.720142291102135]
  Superconductivity and charge density waves are observed in close vicinity in strongly correlated materials. We investigate the nature of such an intertwined state of matter stabilized in the phase diagram of the elementary $t$-$tprime$-$U$ Hubbard model. We provide conclusive evidence that the macroscopic wave functions of the superconducting fragments are well-described by soliton solutions of a Ginzburg-Landau equation.
  arXiv  Detail & Related papers  (2023-07-21T18:00:07Z)
• Topological Superconductivity in Two-Dimensional Altermagnetic Metals [1.779681639954815]
  We study the effect of altermagnetism on the superconductivity of a two-dimensional metal with d-wave altermagnetism and Rashba spin-orbital coupling. We show that a number of topological superconductors, including both first-order and second-order ones, can emerge when the p-wave pairing dominates.
  arXiv  Detail & Related papers  (2023-05-17T18:00:00Z)
• Anisotropic superconductivity of niobium based on its response to non-magnetic disorder [0.0]
  Niobium is one of the most studied superconductors, both theoretically and experimentally. In addition to power applications in alloys, pure niobium is used for sensitive magneto-sensing, radio-frequency cavities, and, more recently, as circuit metallization layers in superconducting qubits.
  arXiv  Detail & Related papers  (2022-07-28T22:24:27Z)
• Thermal self-oscillations in monolayer graphene coupled to a superconducting microwave cavity [58.720142291102135]
  We observe thermal self-oscillations in a monolayer graphene flake coupled to superconducting resonator. The experimental observations fit well with theoretical model based on thermal instability. The modelling of the oscillation sidebands provides a method to evaluate electron phonon coupling in disordered graphene sample at low energies.
  arXiv  Detail & Related papers  (2022-05-27T15:38:41Z)
• Quantum Sensors for Microscopic Tunneling Systems [58.720142291102135]
  tunneling Two-Level-Systems (TLS) are important for micro-fabricated quantum devices such as superconducting qubits. We present a method to characterize individual TLS in virtually arbitrary materials deposited as thin-films. Our approach opens avenues for quantum material spectroscopy to investigate the structure of tunneling defects.
  arXiv  Detail & Related papers  (2020-11-29T09:57:50Z)
• Spin Entanglement and Magnetic Competition via Long-range Interactions in Spinor Quantum Optical Lattices [62.997667081978825]
  We study the effects of cavity mediated long range magnetic interactions and optical lattices in ultracold matter. We find that global interactions modify the underlying magnetic character of the system while introducing competition scenarios. These allow new alternatives toward the design of robust mechanisms for quantum information purposes.
  arXiv  Detail & Related papers  (2020-11-16T08:03:44Z)
• Ferromagnetic Gyroscopes for Tests of Fundamental Physics [49.853792068336034]
  A ferromagnetic gyroscope (FG) is a ferromagnet whose angular momentum is dominated by electron spin polarization and that will precess under the action of an external torque. We model and analyze FG dynamics and sensitivity, focusing on practical schemes for experimental realization.
  arXiv  Detail & Related papers  (2020-10-17T07:13:50Z)
• Waveguide Bandgap Engineering with an Array of Superconducting Qubits [101.18253437732933]
  We experimentally study a metamaterial made of eight superconducting transmon qubits with local frequency control. We observe the formation of super- and subradiant states, as well as the emergence of a polaritonic bandgap. The circuit of this work extends experiments with one and two qubits towards a full-blown quantum metamaterial.
  arXiv  Detail & Related papers  (2020-06-05T09:27:53Z)

This list is automatically generated from the titles and abstracts of the papers in this site.

This site does not guarantee the quality of this site (including all information) and is not responsible for any consequences.