Measurement of the shear strength of a charge-density wave

TL;DR

This study measures the shear strength of charge density waves in niobium triselenide, revealing their relatively low shear modulus compared to longitudinal stiffness and providing insights into their coherence properties.

Contribution

It introduces a novel experimental approach to quantify the shear strength of charge density waves using micro-fabricated samples with thickness steps.

Findings

Shear strength of CDWs is approximately 9.5×10^3 N/m^2.

Lower bound for elastic shear modulus is about 2.1×10^4 N/m^2.

Shear modulus is much smaller than the longitudinal modulus but larger than flux-line lattices.

Abstract

We have explored the shear plasticity of charge density waves (CDWs) in niobium triselenide samples with cross-sections having a single micro-fabricated thickness step. Shear stresses along the step result from thickness-dependent CDW pinning. For small thickness differences the CDW depins elastically at the volume average depinning field. For large thickness differences the thicker, more weakly pinned side depins first via plastic shear. A simple model describes the qualitative features of our data, and yields a value for the CDW's shear strength of approximately 9.5*10^3 N/m^2 and a lower bound for the elastic shear modulus of 2.1*10^4 N/m^2. These values are orders of magnitude smaller than the CDW's longitudinal modulus but are much larger than corresponding values for flux-line lattices, and may explain the relative coherence of the CDW response.