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Sharp transition for single polarons in the one-dimensional Su-Schrieffer-Heeger model
D J J Marchand1, G De Filippis, V Cataudella
1Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada.
Physical Review Letters
|January 15, 2011
Summary
We investigated polarons in the Su-Schrieffer-Heeger (SSH) model, finding a sharp transition in ground-state momentum at critical electron-phonon coupling. This contrasts with smooth transitions seen in other models.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Theoretical Physics
Background:
- Polarons are fundamental quasiparticles in condensed matter systems.
- Understanding polaron behavior is crucial for explaining material properties like conductivity.
- The Su-Schrieffer-Heeger (SSH) model provides a framework for studying electron-phonon interactions.
Purpose of the Study:
- To investigate the behavior of a single polaron within the SSH model.
- To analyze the impact of electron-phonon coupling strength and momentum dependence on polaron properties.
- To identify critical transitions in polaron ground states.
Main Methods:
- Employed four distinct techniques: three numerical and one analytical.
- Studied the polaron in the context of the SSH model, where coupling depends on both electron (k) and phonon (q) momentum.
- Analyzed the crossover from weak to strong electron-phonon coupling (λ).
Main Results:
- Observed a smooth crossover in polaron behavior for coupling dependent only on phonon momentum (q).
- Discovered a sharp, critical transition (at λ(c)) in the SSH model where ground-state momentum shifts from zero to nonzero.
- Found singularities in other polaron properties at this critical coupling strength.
Conclusions:
- The SSH model exhibits a unique critical transition for polarons due to momentum-dependent coupling.
- This finding is generalizable to polarons with coupling dependent on both k and q.
- Results have significant implications for experimental techniques like ARPES and conductivity measurements.
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