Pole skipping from universal hydrodynamics of (1+1)d QFTs
https://arxiv.org/abs/2512.11024
Abstract:
(1+1)d QFTs provide a tractable arena for understanding the emergence of hydrodynamics in thermal states. At high temperatures this process is governed by the weak breaking of conformal symmetry, and so in this limit many features of the hydrodynamic theory that emerges have been argued to be universal. In this paper we study aspects of the stress tensor thermal two-point function in holographic QFTs of this kind and show that they are consistent with the universal hydrodynamic theory proposed to apply at late times. Specifically, we identify the locations of the `pole skipping' points in momentum space at which there is an intersection of poles and zeroes of this two-point function in holographic QFTs. Although these points lie outside the regime where the hydrodynamic theory is controlled, we show that their locations are consistent with those found by resumming the hydrodynamic derivative expansion near the lightcone. For example, this resummation of the universal hydrodynamics correctly predicts the butterfly velocity of holographic theories.
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Quantum Hall antidot as a fractional coulombmeter
Nature Physics Springer Nature
Abstract:
The ability to detect 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. 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 tunneling quasiparticles. 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. We derive a theoretical model that indicates that the differences in the measured charges may be attributed to variations in edge re-equilibration arising from a different parity of downstream integer edge modes. 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 broadly applicable platform to study topological materials.Quantum oscillations in the zeroth Landau Level and the serpentine Landau fan
Physical Review Letters American Physical Society