In-plane Tunneling Spectrum into a [110]-Oriented High-$T_c$ Superconductor in the Pseudogap Regime

摘要

Both the differential tunneling conductance and the surface local density ofstates (LDOS) of a [110]-oriented high-temperature superconductor in thepseudogap (PG) regime are studied theoretically. As a competing candidate forthe mechanism of PG state, the charge-density wave (CDW), spin-density wave(SDW), $d$-density wave (DDW), and d-wave superconducting (DSC) orderings showdistinct features in the tunneling conductance. For the CDW, SDW, and DSCorderings, the tunneling conductance approaches the surface LDOS as the barrierpotential is increased. For the DDW ordering, we show for the first time thatthere exist midgap states at the [110] surface, manifesting themselves as asharp zero-energy peak in the LDOS, as in the case of DSC ordering. However,due to the particle-hole pair nature of the DDW state, these states do notcarry current, and consequently the one-to-one correspondence between thetunneling conductance and the surface LDOS is absent.