Noise and Correlation Study of Quantum Hall Devices

Abstract

We report voltage noise measurements on the cryogenic quantum Hall resistance (QHR) and present two new findings to illustrate the potential of the two-channel instrumentation used. Without applied current, only Johnson-Nyquist noise is present, but at two separate pairs of quantum Hall terminals, it can be cross-correlated via a longitudinal resistance. With applied current, excess noise due to dissipation bursts appears, which increases dramatically with the noninteger fraction of the filling factor.

Nonequilibrium mesoscopic conductance fluctuations as the origin of 1/f noise in epitaxial graphene

“…The current fluctuations caused by the device were obtained by measuring the noise of the voltage drop across a 12.9 k shunt resistor, which was connected to the drain contact of the device and the outer conductor and was cooled to 4 K in a liquid helium storage Dewar. The measured voltage fluctuations were amplified by a low-noise preamplifier [35] (equivalent root mean square input noise voltage: 0.5 nV/ÝHz) and recorded by an analog-to-digital converter model PXI-4461 from National Instruments [36] at a scan rate of 20 000 Hz. Each trace of voltage fluctuations was recorded for 2 sec and subsequently Fourier transformed to obtain a spectrum in the frequency range of 20 to 5000 Hz.…”

Giant Fano factor and bistability in a Corbino disk in the quantum Hall effect breakdown regime

“…Most experiments on QHEBD have been carried out using conventional conductance or resistance measurements in which the time-averaged data are investigated [4,[9][10][11][12][13][14][15][16][17][18]. On the other hand, recently, considerable interest has focused on current noise measurements, which allow electron conduction in the QHEBD state to be investigated in more detail [7,[19][20][21]. Current noise is the fluctuation of the current around its average value over a finite time, which is quantified using the power spectral density, S I .…”

First ac measurements of the quantum Hall effect in epitaxial graphene

“…This is also confirmed by the noise power spectra which are not white but show a 1/f characteristic. The time series look like a random signal, without any indication of burst noise or bi-stable noise as observed at GaAs devices [9]. The excess noise might be related to the onset of the breakdown and it seems to occur mainly in imperfect devices.…”

“…While a low noise figure is essential to precision QHR measurements, this topic has not been studied very much so far. Therefore, we measured the excess noise of a graphene device in a coaxial resistance ratio bridge by means of a lock-in amplifier [14] as well as directly by a digital data acquisition system as described in [9]. Fig.…”

“…In particular, parasitic capacitive effects have to be explored in detail because so far even their magnitude is unknown. Measurements of the magneto capacitance and the associated loss factor [8] as well as noise power measurements [9] of graphene devices may reveal new insights into the quantum Hall effect as well as interesting findings relevant to the application of the quantum Hall effect.…”