Speaker: Dimitri Veras (University of Cambridge)

Title: The Great Escape from Dying Binary Stars and White Dwarfs

Abstract: Extrasolar planets and belts of debris orbiting post-main-sequence single stars may become unbound as the evolving star loses mass. The presence of a binary companion significantly complicates the prospects for orbital excitation and escape. Here, I explore planetary evolution during the post-main sequence, with an emphasis on circumbinary systems. I discuss the implications for the vast free-floating planet population estimated to exist in the Milky Way, the potential pollution of white dwarfs, and the future of the Solar System.

Phasing Out The F Gas Fridge, Wednesday 23rd May, Dept of Physics

Karl G. Sandeman

Department of Physics, Imperial College London, United Kingdom

The fundamental understanding of solid-state phase transitions is crucial to technological innovation. To the most well-known phase transition technologies – colossal magnetoresistance, shape memory, phase change memory, and thermochromic coatings – we need to add magnetic cooling. In the last ten years, research on magnetic phase changes at room temperature has exploded as materials physicists have been drawn to the problem of developing efficient solid-state gas-free refrigeration [1].

This talk will outline the most significant advances in the physics of magnetic refrigerants and will show that the question of what makes an ideal material naturally leads to an investigation of tricritical magneto-elastic phase transitions [2]. By using Mn-based helical metamagnets as a test case, ab initio material modeling and advanced characterisation tools can be shown to provide ways of controlling and optimising magnetic phase transitions for future application [3].

The research leading to these results has received funding from the European Community’s 7th Framework Programme under grant agreement No. 214864 ("SSEEC"). KGS acknowledges financial support from the Royal Society.

References 

[1] A. Turley, Chemistry World 9 48 (2012).

[2] K.G. Sandeman, Scripta Materialia in press (2012) doi: 10.1016/j.scriptamat.2012.02.045

[3] A. Barcza et al., Phys. Rev. Lett. 104 247202 (2010).

Speaker biography

Karl Sandeman is a Lecturer and Royal Society University Research Fellow in the Department of Physics at Imperial College London. He received his undergraduate degree (Natural Sciences) and PhD (Low Temperature Condensed Matter Theory) from the University of Cambridge and
researches room temperature phase transitions. He is currently co-editing a book, Magnetic Cooling: From Fundamentals to High Efficiency Refrigeration, with Oliver Gutfleisch (Wiley, 2012).

Electronic transport in carbon nanotube quantum dots

The talk will focus on aspects of electronic transport in CNT quantum dots -- theoretically, but set firmly in an experimental context. Particular emphasis will be given to zero-bias transport, and the evolution of conductance as a function of gate voltage, temperature and dot-lead tunnel couplings. The symmetry-breaking role of spin-orbit coupling will also be discussed; in particular its interplay with the two regimes of SU(4) Kondo physics towards the centres of the Coulomb blockade valleys, which has rather striking implications for experiment.

Sally Bridgwater, Galbadrakh Dagvadorj and Stepan Ruzicka