Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY, 14853, USA.
Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.
Nat Commun. 2018 Jun 7;9(1):2217. doi: 10.1038/s41467-018-04542-9.
Weyl fermions are a recently discovered ingredient for correlated states of electronic matter. A key difficulty has been that real materials also contain non-Weyl quasiparticles, and disentangling the experimental signatures has proven challenging. Here we use magnetic fields up to 95 T to drive the Weyl semimetal TaAs far into its quantum limit, where only the purely chiral 0th Landau levels of the Weyl fermions are occupied. We find the electrical resistivity to be nearly independent of magnetic field up to 50 T: unusual for conventional metals but consistent with the chiral anomaly for Weyl fermions. Above 50 T we observe a two-order-of-magnitude increase in resistivity, indicating that a gap opens in the chiral Landau levels. Above 80 T we observe strong ultrasonic attenuation below 2 K, suggesting a mesoscopically textured state of matter. These results point the way to inducing new correlated states of matter in the quantum limit of Weyl semimetals.
外尔费米子是最近发现的电子物质关联态的一种成分。一个关键的难题是，实际材料中也包含非外尔准粒子，而厘清实验特征一直具有挑战性。在这里，我们使用高达 95T 的磁场将 Weyl 半金属 TaAs 推至其量子极限，此时仅占据外尔费米子的纯手性 0 阶朗道能级。我们发现，在 50T 以内，电阻率几乎与磁场无关：这对于传统金属来说是不寻常的，但与 Weyl 费米子的手征反常一致。在 50T 以上，我们观察到电阻率呈两个数量级的增加，表明手征朗道能级出现了能隙。在 80T 以上，我们在 2K 以下观察到强烈的超声衰减，表明物质处于介观织构状态。这些结果为在 Weyl 半金属的量子极限中诱导新的关联态物质指明了方向。
