Cuprate diamagnetism in the presence of a pseudogap: Beyond the standard fluctuation formalism

It is often claimed that among the strongest evidence for preformed-pair physics in the cuprates are the experimentally observed large values for the diamagnetic susceptibility and Nernst coefficient. These findings are most apparent in the underdoped regime, where a pseudogap is also evident. While the conventional (Gaussian) fluctuation picture has been applied to address these results, this preformed-pair approach omits the crucial effects of a pseudogap. In this paper we remedy this omission by computing the diamagnetic susceptibility and Nernst coefficient in the presence of a normal state gap. We find a large diamagnetic response for a range of temperatures much higher than the transition temperature. In particular, we report semi-quantitative agreement with the measured diamagnetic susceptibility onset temperatures, over the entire range of hole dopings. Notable is the fact that at the lower critical doping of the superconducting dome, where the transition temperature vanishes and the pseudogap onset temperature remains large, the onset temperature for both diamagnetic and transverse thermoelectric transport coefficients tends to zero. Due to the importance attributed to the cuprate diamagnetic susceptibility and Nernst coefficient, this work helps to clarify the extent to which pairing fluctuations are a component of the cuprate pseudogap.