The metallic ground state in two-dimensional (2D) superconductors has attracted much attention but is still under intense scrutiny. Especially, the measurements in the ultralow temperature region are challenging for 2D superconductors due to the sensitivity to external perturbations. In this work, the resistance saturation induced by external noise, named as the “extrinsic anomalous metallic state”, is observed in 2D transition metal dichalcogenide (TMD) superconductor 4Ha-TaSe₂ nanodevices. However, with further decreasing temperature, credible evidence of the intrinsic anomalous metallic state is obtained by adequately filtering external radiation. Our work indicates that, at ultralow temperatures, the anomalous metallic state can be experimentally revealed as the quantum ground state in 2D crystalline TMD superconductors. Besides, Ising superconductivity revealed by ultrahigh in-plane critical field (B_c2∥) going beyond the Pauli paramagnetic limit (B_p) is detected in 4Ha-TaSe₂, from the one-unit-cell device to the bulk situation, which might be due to the weak coupling between the TaSe₂ submonolayers.

中文翻译：

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过渡金属二硫属化物超导体中的外在和内在异常金属态

二维 (2D) 超导体中的金属基态引起了很多关注，但仍受到严格审查。特别是，由于对外部扰动的敏感性，超低温区域的测量对于二维超导体来说具有挑战性。在这项工作中，在二维过渡金属二硫属化物 (TMD) 超导体 4 Ha -TaSe _{2 中}观察到由外部噪声引起的电阻饱和，称为“外在异常金属态”纳米器件。然而，随着温度的进一步降低，通过充分过滤外部辐射可以获得内在异常金属状态的可信证据。我们的工作表明，在超低温下，异常金属态可以通过实验揭示为二维晶体 TMD 超导体中的量子基态。此外，在 4 Ha -TaSe _{2 中}，从单单元器件到块体情况，都检测到了超出泡利顺磁极限 ( B _p )的超高面内临界场 ( B _c2∥ ) 所揭示的 Ising 超导性，这表明可能是由于 TaSe ₂亚单层之间的弱耦合。