Diamond is an excellent wide-bandgap electrical insulator. However, boron (B) doping is known to induce superconductivity in diamonds. We have performed electrical transport and magnetic measurements under pressure with doping concentrations of (1.4 and 2.6) × 10²¹ cm⁻³, in a temperature range 2 - 10 K and present two interesting effects in superconducting B doped diamond (BDD) thin films: (i) Wohlleben effect (paramagnetic Meissner effect, PME) and (ii) pressure-induced spin glass-like susceptibility anomaly. PME, a low field anomaly in inhomogeneous superconductors, could arise from flux trapping, flux compression, or for non-trivial reason such as emergent Josephson π junctions. The joint occurrence of PME and spin glass type anomalies points to the possible emergence of π junctions. BDD is a disordered s-wave superconductor; and π junctions could be produced by spin-flip scattering of spin ½ moments when present at weak superconducting regions. A frustrated network of 0 and π junctions will result in a distribution of spontaneous equilibrium supercurrents, a spin glass (phase glass) state. Anderson localized spin ½ spinons embedded in a metallic fluid (two-fluid model) could create π junction by spin-flip scattering. Our findings are consistent with the presence of π junctions, invoked to explain the observation of certain resistance anomaly in BDD.

金刚石是一种优良的宽带隙电绝缘体。然而，已知硼 (B) 掺杂会在金刚石中诱导超导性。我们在掺杂浓度为（1.4 和 2.6）×10 ²¹ cm ^{-3的压力下进行了电传输和磁测量}，在 2 - 10 K 的温度范围内，并在超导 B 掺杂金刚石 (BDD) 薄膜中呈现出两个有趣的效应：(i) Wohlleben 效应（顺磁迈斯纳效应，PME）和 (ii) 压力诱导的自旋玻璃样磁化率异常. PME 是非均匀超导体中的一种低场异常，可能由通量俘获、通量压缩或非平凡原因（例如出现的约瑟夫森 π 结）引起。PME 和自旋玻璃型异常的共同出现表明可能出现 π 结。BDD是无序的s波超导体；当存在于弱超导区域时，可以通过自旋 ½ 矩的自旋翻转散射产生 π 结。0 和 π 结的受挫网络将导致自发平衡超电流的分布，即自旋玻璃（相玻璃）状态。嵌入金属流体（双流体模型）中的安德森局部自旋 ½ 旋子可以通过自旋翻转散射产生 π 结。我们的发现与 π 结的存在一致，被用来解释在 BDD 中观察到某些电阻异常。