Low-Frequency Noise and Resistive Switching in $β$-Na$_{0.33}$V$_2$O$_5$

TL;DR

This work investigates how charge order governs transport and resistive switching in the quasi-one-dimensional oxide beta-Na0.33V2O5. The authors combine electrical transport, low-frequency resistance-noise spectroscopy, and temperature-dependent X-ray diffraction on single crystals to track IO and CO transitions and their impact on carrier dynamics. They find a crossover from small-polaron nearest-neighbor hopping with $E_a ~ 63$ meV above $T_{CO} ~ 125$ K to variable-range hopping below $T_{CO}$, accompanied by a sharp suppression of low-frequency noise in the CO state. An applied electric field destabilizes the CO state, producing volatile switching with $R_{OFF}/R_{ON} ~ 10^2$ and a PSD that shifts toward 1/f^2 near switching, linking charge order, electronic correlations, and non-thermal switching with potential cryogenic memory applications.

Abstract

The interplay between charge ordering and its manifestation in macroscopic electrical transport in low-dimensional materials is crucial for understanding resistive switching mechanisms. In this study, we investigate the electronic transport and switching behavior of single-crystalline $β$-Na$_{0.33}$V$_2$O$_5$, focusing on low-frequency resistance noise dynamics of charge-order-driven resistive switching. Using electrical transport, low frequency noise spectroscopy, and X-ray diffraction, we probe electron dynamics across the Na-ion-ordering (IO) and charge-ordering (CO) transitions. Near room temperature, the weak temperature dependence of the noise spectral density points to a dominance of nearest-neighbor polaron hopping. Below IO transition temperature (\( T_{IO} \sim 240 \, \text{K} \)), structural analysis reveals that Na-ions adopt a zig-zag occupancy pattern, breaking the two-fold rotational symmetry and influencing the electronic ground state. Subsequently, a sharp drop in resistance noise below the CO transition temperature (\( T_{CO} \sim 125 \, \text{K} \)) indicates the emergence of correlated electron behavior. Furthermore, application of sufficient electric field leads to the destabilization of the CO state, and a transition to a high-conducting state. The material exhibits distinct resistive switching between 35~K and 110~K, with a resistance change spanning two orders of magnitude, primarily driven by electronic mechanisms rather than Joule heating. These findings provide new insights into charge-order-induced switching and electronic correlations in quasi-one-dimensional systems, with potential applications in cryogenic memory and neuromorphic computing devices owing to the low noise levels in their stable resistive states.

Figures (6)

• Figure 1: Structure of $\beta$-Na$_{0.33}$V$_2$O$_5$, highlighting the arrangement of Na-sites within a tunnel structure and V-O coordination geometry.
• Figure 2: (a) Temperature dependence of resistivity and noise. Error bars represent the standard deviation from three different measurements. (Inset: The derivative of resistance with respect to temperature, highlighting a transition around 125 K). (b) Fitting of the resistivity data to a small polaron nearest-neighbor hopping (NNH) model in the high-temperature regime. (c) Fitting of the resistivity data to a variable-range hopping (VRH) model in the low-temperature regime. (d) Time series of residual voltage fluctuations from the mean at three distinct temperatures (The plots at 300 K and 100 K are shifted upward and downward, respectively, for clarity). (e) Power spectral density of the residual voltage fluctuations derived from (d), illustrating their frequency-dependent ($1/f^\alpha$) noise.
• Figure 3: Temperature-dependent structure transitions in $\beta$-Na$_{0.33}$V$_2$O$_5$. (a) Structure solutions at 100 K, 170 K, and 290 K, with VO$_x$ polyhedra colored according to bond valence sum. Zig-zag ordering of Na-ions and periodic distortions to V–O local structure contribute respectively to 2- and 6-fold cumulative expansions of the unit cell (dashed lines) along $b$. (b) Detector frame images collected at 100 K and 170 K, with several modulation satellites indicated by arrows. (c) Relative modulation satellite intensity vs. temperature. The discontinuity at 170 K results from crystal orientation differences between separate measurements.
• Figure 4: Current-voltage characteristics, measured at various temperatures from T = 50 K to 200 K, display abrupt resistance switching behavior. A current limit of 5 mA was set to prevent permanent damage to the device. $V_{\text{th}}$ is the threshold voltage and $V_{\text{h}}$ is hold voltage.
• Figure 5: (a-d) Voltage-driven noise behavior at $T = 50$ K: (a) Normalized time series showing the temporal evolution of resistance fluctuations. (b) Normalized power spectral density (PSD) of resistance fluctuations, highlighting $1/f^{\alpha}$ behavior; dashed lines are fits to $1/f^{\alpha}$. (c) Noise magnitude at $f = 10$ mHz as a function of applied voltage. (d) Frequency exponent of the PSD, illustrating changes in the noise spectrum with voltage. (e-h) Voltage-driven noise behavior at $T = 200$ K: (e) Normalized time series showing resistance fluctuations over time. (f) Normalized PSD of resistance fluctuations; dashed lines are fits $1/f^{\alpha}$. (g) Noise magnitude at $f = 10$ mHz as a function of applied voltage. (h) Voltage dependence of the frequency exponent of PSD.