Investigating the finite temperature behaviour of polarons through the Momentum Average method and the Generalized Green’s function Cluster Explansion method.

The description of solid state systems form an intractable many-body problem as every particle is pushed and pulled due to Coulomb’s law by the other particles. It is almost impossible to directly describe every particle in a macroscopic system (with 10^24 particles). A clever solution involves simplifying the many-body problem into a problem of hypothetical non-interacting or weakly interacting ‘quasiparticles’ .

One such quasiparticle is the phonon, which represents the quantised vibrations of the lattices sites. When electrons propagate through the lattice, it interacts with phonons. The composite system (i.e the electron dressed by a cloud of phonons) has particle-like properties and are known as polarons. This leads to important consequences in electrical and thermodynamic properties of materials. However, describing the behaviour of polarons has remained one of the most challenging problems in quantum matter. Furthermore, at non-zero temperatures, there is an arbitrary number of thermal phonons in the system which further complicates the study of polarons.

Using a method known as the MA approximation and GGCE, we seek to advance our present understanding of polarons at finite temperature. Outcomes from this study have broad ranging consequences from understanding decoherence in solid-state quantum computing hardware to engineering the materials of tomorrow.

Faculty Supervisor:

Mona Berciu

Student:

Partner:

Yale University

Discipline:

Physics

Sector:

Education

University:

The University of British Columbia

Program: