Sondheimer oscillations as a probe of non-ohmic flow in type-II Weyl semimetal WP${}_2$

Abstract

As conductors in electronic applications shrink, microscopic conduction processes lead to strong deviations from Ohm's law. Depending on the length scales of momentum conserving ($l_{MC}$) and relaxing ($l_{MR}$) electron scattering, and the device size ($d$), current flows may shift from ohmic to ballistic to hydrodynamic regimes and more exotic mixtures thereof. So far, an in situ, in-operando methodology to obtain these parameters self-consistently within a micro/nanodevice, and thereby identify its conduction regime, is critically lacking. In this context, we exploit Sondheimer oscillations, semi-classical magnetoresistance oscillations due to helical electronic motion, as a method to obtain $l_{MR}$ in micro-devices even when $l_{MR}\gg d$. This gives information on the bulk $l_{MR}$ complementary to quantum oscillations, which are sensitive to all scattering processes. We extract $l_{MR}$ from the Sondheimer amplitude in the topological semi-metal WP${}_2$, at elevated temperatures up to $T\sim 50$~K, in a range most relevant for hydrodynamic transport phenomena. Our data on micrometer-sized devices are in excellent agreement with experimental reports of the large bulk $l_{MR}$ and thus confirm that WP${}_2$ can be microfabricated without degradation. Indeed, the measured scattering rates match well with those of theoretically predicted electron-phonon scattering, thus supporting the notion of strong momentum exchange between electrons and phonons in WP${}_2$ at these temperatures. These results conclusively establish Sondheimer oscillations as a quantitative probe of $l_{MR}$ in micro-devices in studying non-ohmic electron flow.

14 pages with 4 figures

References in corpus (6)

• Restoring the density-gradient expansion for exchange in solids and surfaces
• Generalized gradient approximation for solids and their surfaces
• JDFTx: software for joint density-functional theory
• Electron scattering in tantalum monoarsenide
• Evidence for dominant phonon-electron scattering in Weyl semimetal WP${}_2$
• Fermi surface of the Weyl type-II metallic candidate WP2

Cited by in corpus (7)

• Hydrodynamic approach to two-dimensional electron systems
• From low-field Sondheimer oscillations to high-field very large and linear magnetoresistance in a SrTiO${}_3$-based two-dimensional electron gas
• Generalized Design Principles for Hydrodynamic Electron Transport in Anisotropic Metals
• Linear colossal magnetoresistance driven by magnetic textures in LaTiO3 thin films on SrTiO3
• Deep-lying semi-Dirac fermions in hexagonal close-packed cadmium
• Viscoelastic response and anisotropic hydrodynamics in Weyl semimetals
• Scalable Sondheimer oscillations driven by commensurability between two quantizations