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Spin-induced optical conductivity in the spin-liquid candidate herbertsmithite
1Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Physical Review Letters
|October 8, 2013
Summary
We measured the low-frequency optical conductivity of herbertsmithite, a spin-liquid candidate. Spin dynamics contribute to conductivity, showing a power-law frequency dependence consistent with theoretical predictions for a gapless U(1) Dirac spin liquid.
Area of Science:
- Condensed Matter Physics
- Quantum Materials Science
Background:
- Herbertsmithite is a key candidate material for realizing a quantum spin liquid state.
- Understanding the low-frequency dynamics of spin liquids is crucial for their characterization.
Purpose of the Study:
- To directly measure the low-frequency optical conductivity of single-crystal herbertsmithite.
- To investigate the contribution of spin degrees of freedom to conductivity.
- To compare experimental results with theoretical predictions for spin liquid behavior.
Main Methods:
- Terahertz time-domain spectroscopy was employed to probe the optical conductivity.
- Measurements were performed on large-area single-crystal herbertsmithite samples.
- Analysis focused on the real part of the in-plane conductivity (σ(ab)(ω)) below 1.4 THz.
Main Results:
- A distinct contribution to the in-plane conductivity from the spin degree of freedom was observed below 1.4 THz.
- This spin-induced conductivity exhibits a power-law frequency dependence, σ(ab)(ω) ~ ω(β), with an exponent β ≈ 1.4.
- The observed behavior aligns with theoretical models of gapless U(1) Dirac spin liquids.
Conclusions:
- The experimental results provide direct evidence for spin-driven conductivity in herbertsmithite.
- The findings support the theoretical framework of emergent gauge fields in gapless U(1) Dirac spin liquids.
- This study advances the understanding and characterization of quantum spin liquid states in materials.
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