Magnetoresistance Oscillations in Few-Layer NbSe2 in Superconducting Fluctuation Regime

Abstract

Quantum interference phenomena in superconductors, such as Josephson interference and Little-Parks oscillations, serve as powerful probes of phase coherence, symmetry breaking and vortex dynamics. However, they are typically observed in well-defined mesoscopic structures, and their behavior in the two-dimensional limit remains largely unexplored. Here, we report periodic magnetoresistance oscillations, superconducting interference patterns, and interfering diode effect in unpatterned few-layer NbSe2. These phenomena emerge exclusively within the superconducting fluctuation regime of thin samples, consistent with the enhanced anomalous metallic behavior of atomically thin NbSe2. The non-monotonic temperature dependence of both the oscillation amplitude and the diode efficiency can be captured by a model in which thermally activated vortices traverse intrinsic supercurrent loops. Our results reveal that the observed interference phenomena originate from the lost of global phase coherence, providing a new route to accessing interference effects in unpatterned superconductors.

Figures (4)

• Figure 1: (a) Temperature dependence of the normalized resistance of NbSe2 devices of varying thicknesses. The inset shows a schematic of a typical few-layer NbSe2 device. (b) Temperature dependence of the upper critical field for S1, S2, S4 and S5. The orange shaded area marks the region where magnetoresistance oscillations are observed. Inset shows the normalized temperature dependence of $R$ and $d R / d T$ for S2, with the orange shaded region indicating the temperature range where oscillations appear. (c) Temperature-dependent resistance of S1 under different perpendicular magnetic fields shown as Arrhenius plot. (d) Resistance oscillations as a function of perpendicular magnetic field (top panel) and the corresponding background-subtracted resistance $\Delta{R}$ (bottom panel) for S2. (e) Fast Fourier transform of the $\Delta{R}$ versus B in (d). (f) Resistance oscillations as a function of perpendicular magnetic field component $B \cdot \cos (\theta)$ for S3, where $\theta$ is the angle between the magnetic field and the direction perpendicular to the sample plane.
• Figure 2: Thickness dependence of the magnetoresistance oscillation. (a-d) Resistance oscillations as a function of perpendicular magnetic field for a trilayer (a), four-layer (b), six-layer (c) and bulk (d) NbSe2 device at various temperatures.
• Figure 3: (a) Colour maps of the background-subtracted resistance for S2 (4L) as a function of temperature and perpendicular magnetic field. (b) Oscillation amplitude as a function of temperature for device S2. The dashed curve represents five times the amplitude expected from the Little–Parks effect. (c) Colour maps of the differential resistance ($dV/dI$) of S2 as a function of magnetic field and DC bias current at different temperatures. (d) The upper panel shows the field dependence of $I_c^{+}$ and $\left|I_c^{-}\right|$, where the critical currents are defined at $\sim 0.5 \%$ of the normal resistance. The lower panel presents the calculated flux-dependent critical currents $I_c^{+}$ and $\left|I_c^{-}\right|$. (e) Temperature dependence of $I_c^{+}$, $\left|I_c^{-}\right|$, $\Delta I_c$ and $\eta$ for S1 at magnetic field $B=5 \mathrm{mT}$.
• Figure 4: Non-monotonic temperature dependence of the oscillation amplitude for four devices (S1, S2, S3, S4), plotted as $\Delta R / R_n \cdot\left(2 k_B T / E_0\right)^2$ versus $(E_v + E_0/4)/(2k_B T)$. The experimental data for each device are distinguished by different symbols, while the solid black line represents the theoretical model.