Thermoelectric Transport: Progress in First Principles and Other Approaches, and the Interplay with Experiment
CECAM-HQ-EPFL, Lausanne, Switzerland
Atomistic computation of materials’ properties has achieved a high degree of sophistication. In many cases one can predict properties “ab-initio”, without any adjustable parameters. However, electrothermal and thermoelectric transport phenomena have been lagging behind in this respect. One clear example is the thermal conductivity. Even for such common materials as bulk Si and Ge, ab-initio calculation of their lattice thermal conductivity was first accomplished in 2007  (almost 80 years after Peierls wrote the general quantum mechanical equation governing phonon transport in single crystals. ) Similarly, despite continuous developments in the ab-initio theory of electron-phonon coupling , the study of properties such as the thermopower, or the electrical conductivity of thermoelectric materials, has seldom been approached using ab-initio methods, and even then, this was done in the context of a parameterized relaxation time approximation (thus not really ab-initio.)  One possible reason for this delay in the application of predictive computational methodologies to thermoelectric phenomena is the past disconnect between the broader theoretical condensed matter community, which developed most of these techniques, and the thermoelectrics community. Also, until recently the main focus of micro/nano electronics development was placed on charge transport, while less attention was payed to electrothermal phenomena. The current situation has changed, however, as miniaturization has reached limits where charge conduction can no longer be considered in isolation from its associated energy transport, and the study of the combined flow of electrons and phonons in nanostructured systems is of utmost importance. A resurgence of interest in thermoelectric phenomena has taken place since the late 90’s, motivated by the development of nanoscience. The result is an extremely rich and varied range of new strategies towards thermoelectric efficiency improvement. We have seen the development of complex skutterudite materials , superlattices with figures of merit twice as large as the previous state of the art , the discovery of very high Seebeck coefficients in cobaltates , and many others. New phenomena have been observed that often contradict previously accepted belief, like the reduction of thermal conductivity below the “alloy limit” , or the very recent reports of unexpectedly high ZT in silicon, when it is in the form of rough nanowires [9,10]. New materials based on sintered powder , and on embedded nanoparticles , have appeared which still defy theoretical attempts to understand them. The rapid development and implementation of predictive theoretical studies of thermoelectric transport would provide invaluable guidance to experimental efforts such as those mentioned above, and can as well aid in the design of new materials for thermoelectric applications. We believe that the proposed workshop would facilitate progress on the theoretical front and would therefore be extremely beneficial in advancing the thermoelectrics field.
Description of program
The program will cover a broad array of topics at the forefront of thermoelectrics research. Predicitive theoretical methods (such as first principles, molecular dynamics and monte carlo approaches) will be highlighted and their utility in addressing materials design issues for thermoelectrics will be elucidated. Each day will consist of morning and afternoon sessions with oral presentations. Ample time for discussion will be provided in each session. In addition, there will be a late afternoon poster session on the Day 1 and a late afternoon panel discussion on Day 2. The focus of this panel discussion will be: a) to highlight the major current thermoelectrics challenges, b) to elucidate promising future directions and c) to identify and promote possible collaborative efforts between the international group of workshop participants. A summary of the tentative session workshop organization is provided below: Topic 1: Nanostructured Materials for Thermoelectrics (2 Sessions) Session speakers: Giulia Galli, Takao Mori, Ali Shakouri, Natalio Mingo, Sebastian Volz, Gang Chen, Paul Von Allmen, Shidong Wang, M. Roger. Topic 2: Thermal transport in Nanostructured Materials (1 session) Session speakers: Giovanni Cuniberti, Ravi Prasher, Ivana Savic Topic 3: Thermal Transport across Interfaces (1 Session) Session speakers: Keivan Esfarjani, Derek Stewart Topic 4: Materials by Design (2 sessions) Session speakers: Gerald Mahan, Artem Oganov, Joseph Heremans, David Broido, Nathalie Vast, P. Kratzer. Panel Discussion: "Beating the ZT Barrier: Issues and Future Directions"
Natalio Mingo ( French Atomic Energy Commission (CEA), Grenoble ) - Organiser
Nathalie VAST ( CEA - Ecole Polytechnique Palaiseau ) - Organiser
David Broido ( Boston College ) - Organiser
Derek Stewart ( Cornell University ) - Organiser