Enhancement of maximum superconducting temperature by applying pressure and reducing the charge transfer gap
Abstract
Recent Scanning Tunneling Spectra(STS) measurement on underdoped cuprate discovers the increase of the maximum superconducting transition temperature Tc when the size of charge transfer gap (CTG) is reduced. Applying pressure is another well known method to increase maximum Tc. However, these pressure experiments also found another puzzle that Tc is enhanced in underdoped and optimal doped samples but suppressed in overdoped. Here we present a possible mechanism based on the charge fluctuation to explain both these two effects simultaneously. Starting from 3-band Hubbard model, we retrieve the charge fluctuation(CF) between oxygen 2p6 band and copper 3d10 band which is ignored in the t-J model. This model is studied via variational Monte Carlo method(VMC).