Gate-tunable double-dome superconductivity in twisted trilayer graphene

Nature Physics Springer Nature (2025)

Authors:

Zekang Zhou, Jin Jiang, Paritosh Karnatak, Ziwei Wang, Glenn Wagner, Kenji Watanabe, Takashi Taniguch, Christian Schönenberger, Siddharth Ashok Parameswaran, Steven H Simon, Mitali Banerjee

Abstract:

Graphene moiré systems are ideal environments for investigating complex phase diagrams and gaining fundamental insights into the mechanisms that underlie them, as they permit controlled manipulation of electronic properties. Magic-angle twisted trilayer graphene has emerged as a key platform for exploring moiré superconductivity due to the robustness of its superconducting order and the ability to tune its energy bands with an electric field. Here we report the direct observation of two domes of superconductivity in the phase diagram of magic-angle twisted trilayer graphene. The dependence of the superconductivity of doped holes on the temperature, magnetic field and bias current shows that it is suppressed near a specific filling of the moiré flat band, leading to a double dome in the phase diagram within a finite range of the displacement field. The transport properties are also indicative of a phase transition and the potentially distinct nature of superconductivity in the two domes. Hartree–Fock calculations incorporating mild strain yield an incommensurate Kekulé spiral state whose effective spin polarization peaks in the regime where superconductivity is suppressed in the experiments.

Quantum Hall Antidot as a Fractional Coulombmeter

preprint, arXiv:2509.04209

Authors:

Mario Di Luca, Emily Hajigeorgiou, Zekang Zhou, Tevž Lotrič, Tengyan Feng, Kenji Watanabe, Takashi Taniguchi, Steven H. Simon, Mitali Banerjee

Abstract:

The detection of fractionally charged quasiparticles, which arise in the fractional quantum Hall regime, is of fundamental importance for probing their exotic quantum properties. While electronic interferometers have been central to probe their statistical properties, their interpretation is often complicated by bulk-edge interactions. Antidots, potential hills in the quantum Hall regime, are particularly valuable in this context, as they overcome the geometric limitations of conventional designs and act as controlled impurities within a quantum point contact. Furthermore, antidots allow for quasiparticle charge detection through straightforward conductance measurements, replacing the need for more demanding techniques. In this work, we employ a gate-defined bilayer graphene antidot operating in the Coulomb-dominated regime to study quasiparticle tunneling in both integer and fractional quantum Hall states. We show that the gate-voltage period and the oscillation slope directly reveal the charge of the tunneling quasiparticles, providing a practical method to measure fractional charge in graphene. We report direct measurements of fractional charge, finding q=e/3 at ν=4/3, 5/3 and 7/3, q=2e/3 at ν=2/3 and q=3e/5 at ν=3/5, while at ν=8/3 we observe signatures of both e/3 and 2e/3 tunneling charge. The simplicity and tunability of this design open a pathway to extend antidot-based charge measurements to other van der Waals materials, establishing antidots as a powerful and broadly applicable platform to study the quantum Hall effect.

Hydrodynamic memory and Quincke rotation

Physical Review Fluids American Physical Society (APS) 10:9 (2025) 093701

Authors:

Jason K Kabarowski, Aditya S Khair, Rahil N Valani

Active sorting to boundaries in active nematic–passive isotropic fluid mixtures

Soft Matter Royal Society of Chemistry (2025)

Authors:

Saraswat Bhattacharyya, Julia M Yeomans

Abstract:

We use a two-fluid model to study a confined mixture of an active nematic fluid and a passive isotropic fluid. We find that an extensile active fluid preferentially accumulates at a boundary if the anchoring is planar, whereas its boundary concentration decreases for homeotropic anchoring. These tendencies are reversed if the active fluid is contractile. We argue that the sorting results from gradients in the nematic order, and show that the behaviour can be driven by either imposed boundary anchoring or spontaneous anchoring induced by active flows. Our results can be tested by experiments on microtubule-kinesin motor networks, and may be relevant to sorting to the boundary in cell colonies or cancer spheroids.

Nonreciprocal Mixtures in Suspension: The Role of Hydrodynamic Interactions

Physical Review Letters American Physical Society (APS) 135:10 (2025) 108301

Authors:

Giulia Pisegna, Navdeep Rana, Ramin Golestanian, Suropriya Saha

Abstract:

The collective chasing dynamics of nonreciprocally coupled densities leads to stable traveling waves which can be mapped to a model for emergent flocking. In this Letter, we couple the nonreciprocal Cahn-Hilliard model to a fluid to minimally describe scalar active mixtures in a suspension, with the aim to explore the stability of the waves, i.e., the emergent flock in the presence of self-generated fluid flows. We show that the emergent polarity is linearly unstable to perturbations for a specific sign of the active stress recalling instabilities of orientational order in a fluid. Using numerical simulations, we find, however, that nonreciprocity stabilizes the waves against the linear instability in a large region of the phase space.