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Physics Department Colloquia Speakers 2023/24

Here is a list of previous colloquia speakers 2023/24.

Prof Nigel Hussey (University of Bristol, UK and Radboud University, Netherlands)

The allure of linearity: Exploring the link between strange metallicity and high-temperature superconductivity Friday 9 February 2024

In typical metals, the electrical resistivity ρ tends to vanish at the extremes of temperature T and magnetic field strength H, albeit for different reasons. At intermediate temperatures, however, ρ(T) is invariably linear due to the scattering of electrons off phonons – the quantized vibrations of the lattice. Electron-phonon coupling is also responsible for superconductivity in many of these metals. Indeed, a robust correlation exists between the coefficient of the T-linear resistivity α and the superconducting transition temperature Tc; a link enshrined in the old adage “bad metals make good superconductors”.

Despite being discovered almost four decades ago, the high-Tc cuprates still boast the highest ambient-pressure Tc values of all known materials. Intriguingly, a similar correlation betweenα and Tc exists in cuprates too, prompting many in the field to argue that whatever is the cause of this (T-linear) scattering is also the pairing mechanism for high-temperature superconductivity. Despite a prolonged and intense search, however, the origin of this scattering has not been identified. Crucially, the linearity in ρ in cuprates extends over an anomalously broad temperature and field range, implying an unconventional electronic state. Moreover, the magnetoresistance has a linear-in-field slope that also correlates with Tc. In this colloquium, I will discuss the profound implications of these correlations, along with a number of other simple observations linking the (magneto)transport properties of cuprates with their corresponding superconducting properties. Collectively, these observations motivate the search for an entirely new paradigm for high-temperature superconductivity, one in which these T- and H-linearities play a central role.

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