Post-graduate theses
Search command : Author="Στεφανίδης"
And Author="Κωνσταντίνος"
Current Record: 4632 of 6695
|
Identifier |
000388256 |
Title |
Thermal diode by quantum magnets |
Alternative Title |
Θερμική δίοδος με κβαντικούς μαγνήτες |
Author
|
Γεωργιλαδάκης, Ανδρέας Α.
|
Thesis advisor
|
Ζώτος, Ξενοφών
|
Reviewer
|
Τσιρώνης, Γιώργος
Φλυτζάνης, Νικόλαος
|
Abstract |
The propagation of heat in magnetic materials, where we have two heat carriers that interact with each other, is studied in one-dimension. We introduced the spin chain and the spin ladder materials, that have an unusually large magnetic contribution to the total thermal conductivity. After that, we present the phenomenon of thermal rectification in which thermal transport along a specific axis is dependent upon the sign of the temperature gradient or heat current and can offer improved thermal management. We examined under which circumstances this phenomenon is observed, concluding that the thermal conductivities of the materials that we ll use must have temperature dependence, otherwise rectification does not occur. We then focused on two cases, the static thermal rectification and the dynamical thermal rectification. In the first case, in order to calculate the rectification factor we used the heat current equation when in the dynamic case we solved numerically the Bloch-Boltzmann-Peierls equation for the lattice and magnetic degrees of freedom. In both cases, we concluded that the highest rectification is observed in a material that is composed of the spin chain Sr2CuO3 and the spin ladder Ca9La5Cu24O41, bounded together. Lastly, we study the case that we adapt a time-dependent heat source at the left surface of our magnetic material (or a composition of magnetic materials) and we observe the temperature response at the opposite surface, trying to conclude in which cases heat propagates ballistically and in which diffusively. We pointed out that if the phonons’ diffusion time is equal or smaller than the period of the heat source then the heat propagates ballistically, otherwise diffusively.
|
Language |
English |
Subject |
Thermal rectification |
|
Κβαντικός μαγνήτης |
Issue date |
2014-11-21 |
Collection
|
School/Department--School of Sciences and Engineering--Department of Physics--Post-graduate theses
|
|
Type of Work--Post-graduate theses
|
Permanent Link |
https://elocus.lib.uoc.gr//dlib/d/c/4/metadata-dlib-1415089954-443170-29272.tkl
|
Views |
593 |