论文标题
C轴外延丘陵连接处的隧道光谱
Tunneling spectroscopy of c-axis epitaxial cuprate junctions
论文作者
论文摘要
原子上精确的外延结构是最小化疾病外在影响的隧道光谱的独特系统。我们介绍了在外在c轴上进行的一项系统的隧道光谱研究，该研究在广泛的掺杂，温度和偏置范围内la $ _ {2-x} $ sr $ _ {x} $ cuo $ _ {4} $/la $ _ {2} $ cuo $ _ {4} $/la $ _ {2-x} $ _ {2-x} $ sr $ _ {x} $ _ {x} $ cuo $ _ {4} $ _ {4} $ _ {4} $ {4} $ HETEROSURS。这些超导体/绝缘体/超导体（SIS）设备的行为是不寻常的。降至20 MK，完全抑制了C轴约瑟夫森的临界电流，其屏障仅为2 nm $ _ {2} $ cuo $ _ {4} $，零偏置电导率仍为正常状态的20-30％，这意味着实质的人口含量为gap状态。隧道光谱显示出极大的抑制连贯峰。随着温度的升高，超导间隙填充而不是以$ t_ {c} $关闭。对于所有掺杂级别，光谱以$ \ sim $ 80 meV显示了一个非弹性隧道功能，被压制为$ t $超过$ t_ {c} $。这些名义上简单的外延丘陵连接处明显偏离基于标准的Bardeen-Cooper-Schrieffer（BCS）理论的期望。
Atomically precise epitaxial structures are unique systems for tunneling spectroscopy that minimize extrinsic effects of disorder. We present a systematic tunneling spectroscopy study, over a broad doping, temperature, and bias range, in epitaxial c-axis La$_{2-x}$Sr$_{x}$CuO$_{4}$/La$_{2}$CuO$_{4}$/La$_{2-x}$Sr$_{x}$CuO$_{4}$ heterostructures. The behavior of these superconductor/insulator/superconductor (SIS) devices is unusual. Down to 20 mK there is complete suppression of c-axis Josephson critical current with a barrier of only 2 nm of La$_{2}$CuO$_{4}$, and the zero-bias conductance remains at 20-30% of the normal-state conductance, implying a substantial population of in-gap states. Tunneling spectra show greatly suppressed coherence peaks. As the temperature is raised, the superconducting gap fills in rather than closing at $T_{c}$. For all doping levels, the spectra show an inelastic tunneling feature at $\sim$ 80 meV, suppressed as $T$ exceeds $T_{c}$. These nominally simple epitaxial cuprate junctions deviate markedly from expectations based on the standard Bardeen-Cooper-Schrieffer (BCS) theory.
