arXiv subjects

Akinori Kamiyama

Publications and source records attributed to Akinori Kamiyama.

5 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↗

arXiv2025

Electrically induced bulk and edge excitations in the fractional quantum Hall regime

We apply a voltage pulse to electrically excite the incompressible region of a two-dimensional electron liquid in the $ν=2/3$ fractional quantum Hall state and investigate the collective excitations in both the edge and bulk via photoluminescence spectral energy shifts. Introducing an offset in the voltage pulse significantly enhances the excitation signal. Real-space and time-resolved measurements reveal the dynamics of the bulk excitations, with an estimated group velocity of approximately $3 \times 10^4$ m/s. These bulk excitations align well with the magneto-plasmon model. Our results highlight the topological link between edge and bulk states, providing a novel approach to exploring solid-state analogs of quantum gravity.

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↗