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arXiv 2205.05087cond-mat.supr-concond-mat.mtrl-scicond-mat.str-el
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Bernal双层石墨烯的自旋轨道增强超导电性

Spin-Orbit Enhanced Superconductivity in Bernal Bilayer Graphene

Yiran Zhang, Robert Polski, Alex Thomson, Étienne Lantagne-Hurtubise, Cyprian Lewandowski, Haoxin Zhou, Kenji Watanabe, Takashi Taniguchi, Jason Alicea, Stevan Nadj-Perge

摘要:

在大的垂直电场存在下,Bernal堆叠双层石墨烯(BLG)具有几种对称性破缺的金属相以及磁场诱导的超导电性。然而,超导态是相当脆弱的,只出现在一个狭窄的密度窗口和最大临界温度$T_c\approx30$ ~mK。在这里,我们表明,放置单层钨二硒化物(WSe $_{2}$)的BLG促进库珀配对到一个非凡的程度:超导性出现在零磁场,表现出一个数量级的增强$T_c$,并发生在一个密度范围更宽的8倍。通过映射量子振荡在BLG-WSe $_2$作为电场和掺杂的函数,我们建立了超导性出现在整个区域的正常状态是极化的,与四个自旋谷味占主导地位。面内磁场测量进一步揭示了临界场对掺杂的显著依赖性,超导圆顶的一端大致遵守Pauli极限,而另一端则严重违反。此外,超导电性只出现在垂直电场中,将BLG空穴波函数推向WSe $_2$ -这表明邻近诱导(伊辛)自旋轨道耦合在增强配对中起着关键作用。我们的研究结果为工程坚固,高度可调和超清洁的石墨烯基超导体铺平了道路。

英文摘要:

In the presence of a large perpendicular electric field, Bernal-stacked bilayer graphene (BLG) features several broken-symmetry metallic phases as well as magnetic-field-induced superconductivity. The superconducting state is quite fragile, however, appearing only in a narrow window of density and with a maximum critical temperature $T_c\approx30$~mK. Here, we show that placing monolayer tungsten diselenide (WSe$_{2}$) on BLG promotes Cooper pairing to an extraordinary degree: superconductivity appears at zero magnetic field, exhibits an order of magnitude enhancement in $T_c$, and occurs over a density range that is wider by a factor of eight. By mapping quantum oscillations in BLG-WSe$_2$ as a function of electric field and doping, we establish that superconductivity emerges throughout a region whose normal state is polarized, with two out of four spin-valley flavours predominantly populated. In-plane magnetic field measurements further reveal a striking dependence of the critical field on doping, with the Chandrasekhar-Clogston (Pauli) limit roughly obeyed on one end of the superconducting dome yet sharply violated on the other. Moreover, the superconductivity arises only for perpendicular electric fields that push BLG hole wavefunctions towards WSe$_2$ -- suggesting that proximity-induced (Ising) spin-orbit coupling plays a key role in enhancing the pairing. Our results pave the way for engineering robust, highly tunable, and ultra-clean graphene-based superconductors.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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