arXiv subjects

John N. Moore

Publications and source records attributed to John N. Moore.

9 recordsLinked to original sources

arXiv2026

Direct observation of the transverse near field of an edge excitation in a fractional quantum Hall state

Stroboscopic time-resolved photoluminescence (PL) microscopy and spectroscopy reveal that an electrically launched edge excitation in a $μ= 1/3$ fractional quantum Hall (FQH) state produces an immediate PL response extending more than 30 $μ$m into the bulk transverse to the edge when the edge magnetoplasmon (EMP) passes the mesa boundary. The nearly instantaneous nature and downstream-only appearance of this long-range response identify it as the non-radiative, quasi-electrostatic near field. We also observe a broad delayed response near the mesa boundary that evolves on a much slower time scale and gradually extends into the bulk. The coexistence of the immediate near-field response and this broad delayed response shows that an electrically launched edge excitation cannot be understood solely as a one-dimensional mode propagating along the boundary, but must instead be viewed as a structure extending in both space and time into the surrounding FQH fluid.

cond-mat.mes-hall↗

arXiv2026

Spatiotemporal imaging of gate-controlled multipath dynamics of fractional quantum Hall edge excitations

Quantum Hall edge excitations, whose low-energy behavior admits a chiral conformal-field-theory description, are a promising platform for engineered dynamical experiments, including analog-spacetime proposals. However, establishing their edge dynamics in realistic electrostatic landscapes is essential for controlled dynamical experiments and has remained experimentally challenging. Here we report spatiotemporal imaging of gate-controlled multipath dynamics of edge excitations in a $ν= 1/3$ fractional quantum Hall device using stroboscopic time-resolved photoluminescence microscopy and spectroscopy with $\sim$100-ps resolution. By tuning a control-gate-defined potential landscape, we observe switching between mesa-defined and gate-defined trajectories and identify an intermediate regime in which a single launched excitation accesses multiple pathways. Time-resolved measurements at downstream locations reveal gate-dependent arrival times and pronounced temporal broadening, showing that the propagation dynamics are strongly modified by the local confinement and become increasingly dispersive in a multipath landscape. We further observe a long-range transverse optical response extending tens of micrometers into the bulk and persisting over distances exceeding 200 $μ$m downstream, consistent with the near-field component of an edge magnetoplasmon. These results establish direct experimental access to controllable multipath edge dynamics in the fractional quantum Hall regime and suggest a platform for engineered nonequilibrium and interference-based experiments, as well as future analog-spacetime studies in quantum Hall edge systems.

cond-mat.mes-hall↗

arXiv2022

Dynamics of the fractional quantum Hall edge probed by stroboscope measurements of trions

By using observations from pump-probe stroboscopic confocal microscopy and spectroscopy, we demonstrate the dynamics of trions and the fractional quantum Hall edge on the order of $\sim1$ ps. The propagation of the quantum Hall edge state excited by a voltage pulse is detected as a temporal change in reflectance in the downstream edge probed by optical pulses synchronized with the voltage pulse. The temporal resolution of such stroboscopic pump-probe measurements is as fast as the duration time of the probe pulse ($\sim1$ ps). This ultra-fast stroboscope measurement enables us to distinguish between the normal mode of edge excitation, known as the edge magneto-plasmon or charge density wave, and other high-energy non-linear excitations. This is the only experimental method available to study the ultra-fast dynamics of quantum Hall edges, and makes it possible to derive the metric tensor $g_{μν}$ of the $(1+1)=2$-dimensional curved spacetime in quantum universe and black hole analogs implemented in the quantum Hall edge.

cond-mat.mes-hall↗

arXiv2022

Real-time and -space visualization of excitations of the ν= 1/3 fractional quantum Hall edge

We present scanning optical stroboscopic confocal microscopy and spectroscopy measurements wherein three degrees of freedom, namely energy, real-space, and real-time, are resolvable. The edge-state propagation is detected as a temporal change in the optical response in the downstream edge. We succeeded in visualizing the excited states of the most fundamental fractional quantum Hall (FQH) state and the collective excitations near the edge. The results verify the current understanding of the edge excitation and also point toward further dynamics outside the edge channel.

cond-mat.mes-hall↗

arXiv2020

Ultra-fast calorimetric measurements of the electronic heat capacity of graphene

Heat capacity is an invaluable quantity in condensed matter physics, yet it has been so far experimentally inaccessible in two-dimensional (2D) van der Waals (vdW) materials, owing to their ultra-fast thermal relaxation times and the lack of suitable nano-scale thermometers. Here, we demonstrate a novel thermal relaxation calorimetry scheme that allows the first measurements of the electronic heat capacity of graphene Ce. It is enabled by the grouping of a radio-frequency Johnson noise thermometer, which can measure the electronic temperature Te with a measurement sensitivity of δTe ~ 20 mK, and an ultra-fast photo-mixed optical heater, which can simultaneously modulate Te with a frequency of up to Ω=0.2 THz. This combination allows record sensitive and record fast measurements of the electronic heat capacity Ce < 10^(-19) J/K, with an electronic thermal relaxation time τe < 10^(-13), representing orders of magnitude improvements as compared to previous state-of-the-art calorimeters. These features embody a breakthrough in heat capacity metrology of nano-scale and low-dimensional systems, and provide a new avenue for the investigation of their thermodynamic quantities.

cond-mat.mes-hall↗

arXiv2020

A liquid nitrogen cooled superconducting transition edge sensor with ultra-high responsivity and GHz operation speeds

Photodetectors based on nano-structured superconducting thin films are currently some of the most sensitive quantum sensors and are key enabling technologies in such broad areas as quantum information, quantum computation and radio-astronomy. However, their broader use is held back by the low operation temperatures which require expensive cryostats. Here, we demonstrate a nitrogen cooled superconducting transition edge sensor, which shows orders of magnitude improved performance characteristics of any superconducting detector operated above 77K, with a responsivity of 9.61x10^4 V/W, noise equivalent power of 15.9 fW/Hz-1/2 and operation speeds up to GHz frequencies. It is based on van der Waals heterostructures of the high temperature superconductor Bi2Sr2CaCu2O8, which are shaped into nano-wires with ultra-small form factor. To highlight the versatility of the detector we demonstrate its fabrication and operation on a telecom grade SiN waveguide chip. Our detector significantly relaxes the demands of practical applications of superconducting detectors and displays its huge potential for photonics based quantum applications.

physics.app-ph↗

arXiv2018

Spontaneous Transition to a Correlated Phase of Skyrmions Observed in Real Space

We conduct photoluminescence microscopy that is sensitive to both electron and nuclear spin polarization to investigate the changes that occur in the magnetic ordering in the vicinity of the first integer quantum Hall state in a GaAs 2D electron system (2DES). We observe a discontinuity in the electron spin polarization and nuclear spin longitudinal relaxation time which heralds a spontaneous transition to a phase of magnetic skyrmions. We image in real space the spin phase domains that coexist at this transition, and observe hysteresis in their formation as a function of the 2DES's chemical potential. Based on measurements in a tilted magnetic field orientation, we found that the transition is protected by an energy gap containing the Zeeman energy, and conclude that the skyrmions here have formed as an ensemble.

cond-mat.str-el↗

arXiv2016

Hyperfine-controlled domain-wall motion observed in real space and time

We perform real-space imaging of propagating magnetic domains in the fractional quantum Hall system using spin-sensitive photoluminescence microscopy. The propagation is continuous and proceeds in the direction of the conventional current, i.e. opposite to the electron flow direction. The mechanism of motion is shown to be connected to polarized nuclear spins around the domain walls. The propagation velocity increases when nuclei are depolarized, and decreases when the source-drain current generating this nuclear polarization is increased. We discuss how these phenomena may arise from spin interactions along the domain walls.

cond-mat.mes-hall↗

arXiv2016

Non-equilibrium fractional quantum Hall states visualized by optically detected MRI

Using photoluminescence microscopy enhanced by MRI, we visualize in real space both electron and nuclear polarization occurring in non-equilibrium FQH liquids. We observe stripe-like regions comprising FQH excited states which discretely form when the FQH liquid is excited by a source-drain current. These regions are topologically protected and deformable, and give rise to bidirectionally polarized nuclear spins as spin-resolved electrons flow across their boundaries.

cond-mat.mes-hall↗