Two-Gap Features from Tunneling Studies on Trilayered Cuprates, HgBa_(2)Ca_(2)Cu_(3)O_(8+delta) with T_(C)approx132K

摘要

We present point contact tunneling spectroscopy measured on nearly optimally-doped HgBa_(2)Ca_(2)Cu_(3)O_(y) (Hg1223) with T_(C)approx132K. The tunneling conductances on Hg1223 exhibit two kinds of gaps that originate from crystallographically inequivalent inner four-fold CuO_(2) plane (IP) and outer five-fold CuO_(2) planes (OP). The averaged-gap magnitude at OP, (DELTA)_(av)(OP), is 37.8 meV but that at IP, (DELTA)_(av)(IP), is 55.9 meV. This result shows that in multilayered cuprates such as Hg1223 the superconducting density of states at IP is different from that at OP, suggesting the existence of two Fermi surfaces.