Experimental aspects of quantum criticality in het quantum Hall regime

We demonstrate that plasma discharge — in both atmospheric dielectric barrier discharge (DBD) and Hall effect thruster (HET) iodine plasma configurations — constitutes a practical hardware quantum random number generator (QRNG). A $35 atmospheric DBD device using a flyback transformer recovered from a discarded CRT television generates a physical entropy stream satisfying NIST SP 800-90B requirements. A zero-additional-cost iodine plasma QRNG derived from the GHT-1 Hall effect thruster uses its existing INA219 I²C current sensor to harvest quantum entropy from the 200V DC iodine discharge — giving the thruster a dual function as both propulsion system and flight-grade QRNG. Both implementations produce output satisfying NIST SP 800-22. Complete open-hardware designs are provided.We demonstrate that plasma discharge — in both atmospheric dielectric barrier discharge (DBD) and Hall effect thruster (HET) iodine plasma configurations — constitutes a practical hardware quantum random number generator (QRNG). A $35 atmospheric DBD device using a flyback transformer recovered from a discarded CRT television generates a physical entropy stream satisfying NIST SP 800-90B requirements. A zero-additional-cost iodine plasma QRNG derived from the GHT-1 Hall effect thruster uses its existing INA219 I²C current sensor to harvest quantum entropy from the 200V DC iodine discharge — giving the thruster a dual function as both propulsion system and flight-grade QRNG. Both implementations produce output satisfying NIST SP 800-22. Complete open-hardware designs are provided.

Jul 31, 20260 citations

Universality and phase diagram in the quantum Hall effect

L. W. Wong

Jan 1, 19970 citations

Natural anomalous cyclotron response in a hydrodynamic local quantum critical metal in a periodic potential

Nicolas Chagnet, Sam Arend, Floris Balm +3 more

We study DC magnetotransport in a quantum critical metal in the presence of a lattice. In the regime where the transport is hydrodynamical the interplay of the Lorentz force and the lattice gives rise to a natural anomalous contribution to the cyclotron frequency that changes it from its canonical charge-to-mass ratio. The size of this effect is universal as it is determined only by thermodynamic quantities. Remarkably the Drude weight changes in such a way that to first subleading order in the lattice strength the Hall resistivity and Hall coefficient do not change, though the Hall angle does change. We confirm our results with numerical simulations in a holographic model of a strange metal. For weak lattice strength these hydrodynamic effects are shown to be present. The numerical simulations also suggest that strong lattice effects beyond a hydrodynamic regime may provide a resolution to the experimentally observed anomalous Hall response of cuprate strange metals.We study DC magnetotransport in a quantum critical metal in the presence of a lattice. In the regime where the transport is hydrodynamical the interplay of the Lorentz force and the lattice gives rise to a natural anomalous contribution to the cyclotron frequency that changes it from its canonical charge-to-mass ratio. The size of this effect is universal as it is determined only by thermodynamic quantities. Remarkably the Drude weight changes in such a way that to first subleading order in the lattice strength the Hall resistivity and Hall coefficient do not change, though the Hall angle does change. We confirm our results with numerical simulations in a holographic model of a strange metal. For weak lattice strength these hydrodynamic effects are shown to be present. The numerical simulations also suggest that strong lattice effects beyond a hydrodynamic regime may provide a resolution to the experimentally observed anomalous Hall response of cuprate strange metals.

arXiv:2409.11095Sep 17, 20240 citations

Screening-controlled dynamical criticality in the quantum Hall regime

Tanima Chanda, Simrandeep Kaur, Anantbir Virk +5 more

At continuous electronic phase transitions, Coulomb interactions can modify the relation between length, energy, and temperature, but experimentally disentangling their effects on spatial versus dynamical criticality has remained difficult, since finite-temperature scaling alone measures only the combined exponent $κ= 1/(zγ)$ . Here, we introduce two advances that resolve this limitation. First, by combining temperature scaling with independent current scaling, we separately extract the dynamical exponent $z$ and the localization-length exponent $γ$ at the quantum Hall plateau transition -- rather than inferring one from an assumed value of the other. Second, using dual-graphite-gated graphene devices in which the effective Coulomb interaction range is tuned geometrically by the ratio of the magnetic length $l_B$ to the graphite-gate distance $d$ , we track this separation across both screened and unscreened interaction regimes within the same device platform. Temperature scaling gives $κ\simeq 0.21$ in the screened regime and $κ\simeq 0.41$ in the unscreened regime; combining this with current scaling reveals that screening changes $z$ from $\simeq 1$ in the unscreened regime to $\simeq 2$ in the screened regime. In contrast, $γ$ remains close to $2.4$ throughout. Our results establish that gate-controlled screening selectively modifies the interaction-dependent dynamical sector of the quantum Hall transition, leaving the localization-length exponent $γ$ unchanged within experimental uncertainty. More broadly, this work establishes geometric screening as a versatile tool for controlling interactions and disentangling interaction and disorder effects in correlated two-dimensional systems, including fractional quantum Hall states, moiré materials, and other strongly localized electronic phases.At continuous electronic phase transitions, Coulomb interactions can modify the relation between length, energy, and temperature, but experimentally disentangling their effects on spatial versus dynamical criticality has remained difficult, since finite-temperature scaling alone measures only the combined exponent $κ= 1/(zγ)$. Here, we introduce two advances that resolve this limitation. First, by combining temperature scaling with independent current scaling, we separately extract the dynamical exponent $z$ and the localization-length exponent $γ$ at the quantum Hall plateau transition -- rather than inferring one from an assumed value of the other. Second, using dual-graphite-gated graphene devices in which the effective Coulomb interaction range is tuned geometrically by the ratio of the magnetic length $l_B$ to the graphite-gate distance $d$, we track this separation across both screened and unscreened interaction regimes within the same device platform. Temperature scaling gives $κ\simeq 0.21$ in the screened regime and $κ\simeq 0.41$ in the unscreened regime; combining this with current scaling reveals that screening changes $z$ from $\simeq 1$ in the unscreened regime to $\simeq 2$ in the screened regime. In contrast, $γ$ remains close to $2.4$ throughout. Our results establish that gate-controlled screening selectively modifies the interaction-dependent dynamical sector of the quantum Hall transition, leaving the localization-length exponent $γ$ unchanged within experimental uncertainty. More broadly, this work establishes geometric screening as a versatile tool for controlling interactions and disentangling interaction and disorder effects in correlated two-dimensional systems, including fractional quantum Hall states, moiré materials, and other strongly localized electronic phases.

arXiv:2607.09244Jul 10, 20260 citations

κ= 1/(zγ)

. Here, we introduce two advances that resolve this limitation. First, by combining temperature scaling with independent current scaling, we separately extract the dynamical exponent

z

and the localization-length exponent

γ

at the quantum Hall plateau transition -- rather than inferring one from an assumed value of the other. Second, using dual-graphite-gated graphene devices in which the effective Coulomb interaction range is tuned geometrically by the ratio of the magnetic length

l_B

to the graphite-gate distance

d

, we track this separation across both screened and unscreened interaction regimes within the same device platform. Temperature scaling gives

κ\simeq 0.21

in the screened regime and

κ\simeq 0.41

in the unscreened regime; combining this with current scaling reveals that screening changes

z

from

\simeq 1

in the unscreened regime to

\simeq 2

in the screened regime. In contrast,

γ

remains close to

2.4

throughout. Our results establish that gate-controlled screening selectively modifies the interaction-dependent dynamical sector of the quantum Hall transition, leaving the localization-length exponent

γ

unchanged within experimental uncertainty. More broadly, this work establishes geometric screening as a versatile tool for controlling interactions and disentangling interaction and disorder effects in correlated two-dimensional systems, including fractional quantum Hall states, moiré materials, and other strongly localized electronic phases.