Hen Bar, Shelukhin Victor, Greenberg Eran, Rozenberg Gregory Kh, Kapitulnik Aharon, Palevski Alexander
Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, Tel Aviv 69978, Israel.
Center for Advanced Radiation Sources, University of Chicago, Chicago, IL 60637, United States of America.
J Phys Condens Matter. 2022 Jan 20;34(13). doi: 10.1088/1361-648X/ac48bf.
Experiments investigating magnetic-field-tuned superconductor-insulator transition (HSIT) mostly focus on two-dimensional material systems where the transition and its proximate ground-state phases, often exhibit features that are seemingly at odds with the expected behavior. Here we present a complementary study of a three-dimensional pressure-packed amorphous indium-oxide (InOx) powder where granularity controls the HSIT. Above a low threshold pressure of ∼0.2 GPa, vestiges of superconductivity are detected, although neither a true superconducting transition nor insulating behavior are observed. Instead, a saturation at very high resistivity at low pressure is followed by saturation at very low resistivity at higher pressure. We identify both as different manifestations of anomalous metallic phases dominated by superconducting fluctuations. By analogy with previous identification of the low resistance saturation as a 'failed superconductor', our data suggests that the very high resistance saturation is a manifestation of a 'failed insulator'. Above a threshold pressure of ∼6 GPa, the sample becomes fully packed, and superconductivity is robust, withtunable with pressure. A quantum critical point at∼ 25 GPa marks the complete suppression of superconductivity. For a finite pressure below, a magnetic field is shown to induce a HSIT from a true zero-resistance superconducting state to a weakly insulating behavior. Determining the critical field,, we show that similar to the 2D behavior, the insulating-like state maintains a superconducting character, which is quenched at higher field, above which the magnetoresistance decreases to its fermionic normal state value.
研究磁场调谐超导体-绝缘体转变（HSIT）的实验大多集中在二维材料系统，其中该转变及其邻近的基态相常常表现出与预期行为似乎不一致的特征。在此，我们展示了对三维压力填充非晶氧化铟（InOx）粉末的补充研究，其中粒度控制着HSIT。在约0.2 GPa的低阈值压力以上，检测到超导的痕迹，尽管既未观察到真正的超导转变，也未观察到绝缘行为。相反，在低压下非常高的电阻率处出现饱和，随后在高压下非常低的电阻率处出现饱和。我们将两者都识别为以超导涨落为主导的反常金属相的不同表现形式。通过类比之前将低电阻饱和识别为“失败的超导体”，我们的数据表明非常高的电阻饱和是“失败的绝缘体”的一种表现形式。在约6 GPa的阈值压力以上，样品变得完全致密，并且超导性很强，且可随压力调节。在约25 GPa处的量子临界点标志着超导性的完全抑制。对于低于该值（25 GPa）的有限压力，磁场被证明会诱导从真正的零电阻超导态到弱绝缘行为的HSIT。通过确定临界场，我们表明与二维行为类似，类绝缘态保持超导特性，该特性在更高场强下被淬灭，高于此场强磁阻降至其费米子正常态值。
