The search for a Fermi surface in the absence of a conventional Fermi liquid has thus far yielded very few potential candidates. Among promising materials are spin-frustrated Mott insulators near the insulator–metal transition, where theory predicts a Fermi surface associated with neutral low-energy excitations. Here we reveal another route to experimentally realize a Fermi surface in the absence of a Fermi liquid by the experimental study of a Kondo insulator SmB₆ positioned close to the insulator–metal transition. We present experimental signatures down to low temperatures (≪1 K) associated with a Fermi surface in the bulk, including a sizeable linear specific heat coefficient, and on the application of a finite magnetic field, bulk magnetic quantum oscillations, finite quantum oscillatory entropy, and substantial enhancement in thermal conductivity well below the charge gap energy scale. Thus, the weight of evidence indicates that despite an extreme instance of Fermi liquid breakdown in Kondo insulating SmB₆, a Fermi surface arises from novel itinerant low-energy excitations that couple to magnetic fields, but not weak DC electric fields.

迄今为止，在不存在常规费米液体的情况下寻找费米表面的可能性很小。在有前途的材料中，靠近绝缘体-金属过渡层的自旋受挫的Mott绝缘体，据理论预测，费米表面与中性低能激发有关。在这里，我们通过对Kondo绝缘子SmB ₆靠近绝缘子-金属过渡层进行实验研究，揭示了在不存在费米液体的情况下通过实验实现费米表面的另一条途径。我们展示了低温下的实验签名（≪1 K）与主体中的费米表面相关，包括相当大的线性比热系数，并且在施加有限磁场时，主体磁量子振荡，有限量子振荡熵和导热率大大提高，远低于电荷缺口能级。因此，有力的证据表明，尽管在Kondo绝缘SmB _6中发生了费米液体的极端破坏，但费米表面还是由耦合到磁场而不是弱的直流电场的新型流动性低能激发产生的。