标题： 基于间接隧穿的自发时间反演对称性破缺和约瑟夫森二极管效应在TiN/Al$_2$O$_3$/Hf$_{0.8}$Zr$_{0.2}$O$_2$/Nb隧道结中的研究 显示英文标题

标题： Indirect Tunneling Enabled Spontaneous Time-Reversal Symmetry Breaking and Josephson Diode Effect in TiN/Al$_2$O$_3$/Hf$_{0.8}$Zr$_{0.2}$O$_2$/Nb tunnel junctions

摘要： 约瑟夫森二极管（JD）效应在约瑟夫森隧道结（JTJ）中的发现引起了广泛关注，因为它对于基于超导电路的量子技术的发展具有重要意义。 迄今为止，在半导体工业技术制备的任何JTJ中，尚未实现高度期望的JD效应的电学控制。 我们报告了采用互补金属氧化物半导体（CMOS）兼容的原子层沉积（ALD）技术制备的具有Al$_2$O$_3$和 Hf$_{\mathrm{0.8}}$Zr$_\mathrm{0.2}$O$_2$复合隧道势垒的JTJ的制造。 这些JTJ在名义零磁场下被发现表现出JD效应，并且通过电训练电流可以控制非互易性，产生出乎意料的大二极管效率，这一效率之前未曾实现。 研究发现，通过准粒子隧穿建立JTJ中的约瑟夫森耦合并未显示出非互易性。 我们将这些观察归因于同时存在正负约瑟夫森耦合，其中后者源于间接隧穿。 结果显示，自发的时间反演对称性破缺以及电阻和电容分流结（RCSJ）模型中相位差的双井势垒图能够完全解释实验观测到的JD效应。 显示英文摘要

摘要： Josephson diode (JD) effect found in Josephson tunnel junctions (JTJs) has attracted a great deal of attention due to its importance for developing superconducting circuitry based quantum technologies. So far, the highly desirable electrical control of the JD effect has not been demonstrated in any JTJ prepared by techniques used in semiconductor industry. We report the fabrication of JTJs featuring a composite tunnel barrier of Al$_2$O$_3$ and Hf$_{\mathrm{0.8}}$Zr$_\mathrm{0.2}$O$_2$ prepared by complementary-metal-oxide-semiconductor (CMOS) compatible atomic layer deposition (ALD). These JTJs were found to show the JD effect in nominally zero magnetic fields with the nonreciprocity controllable using an electric training current, yielding a surprisingly large diode efficiency not achieved previously. The quasiparticle tunneling, through which the Josephson coupling in a JTJ is established, was found to show no nonreciprocity. We attribute these observations to the simultaneous presence of positive and negative Josephson couplings, with the latter originating from indirect tunneling. The resulted spontaneous time-reversal symmetry breaking and the double-minima washboard potential for the ensemble averaged phase difference in the resistively and capacitively shunted junction (RCSJ) model are shown to fully account for the experimentally observed JD effect.