Quantum Griffiths Singularity in a Three-Dimensional Superconductor to Anderson Critical Insulator Transition
Shichao Qi, Yi Liu, Ziqiao Wang, Fucong Chen, Qian Li, Haoran Ji, Rao Li, Yanan Li, Jingchao Fang, Haiwen Liu, Fa Wang, Kui Jin, X. C. Xie, Jian Wang
DOI 10.1103/PhysRevLett.133.226001 · Physical Review Letters
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Abstract
Disorder is ubiquitous in real materials and can have dramatic effects on quantum phase transitions. Originating from the disorder enhanced quantum fluctuation, quantum Griffiths singularity (QGS) has been revealed as a universal phenomenon in quantum criticality of low-dimensional superconductors. However, due to the weak fluctuation effect, QGS is very challenging to detect experimentally in three-dimensional (3D) superconducting systems. Here we report the discovery of QGS associated with the quantum phase transition from 3D superconductor to Anderson critical insulator in a spinel oxide MgTi2O4 (MTO). Under both perpendicular and parallel magnetic field, the dynamical critical exponent diverges when approaching the quantum critical point, demonstrating the existence of 3D QGS. Among 3D superconductors, MTO shows a relatively strong fluctuation effect featured as a wide superconducting transition region. The enhanced fluctuation, which may arise from the mobility edge of Anderson localization, finally leads to the occurrence of 3D quantum phase transition and QGS. Our findings offer a new perspective to understand quantum phase transitions in strongly disordered 3D systems.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| MgTi2O4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 5.6 | Pressure not reported | onset |
| MgTi2O4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 2.88 | Pressure not reported | zero_resistance |
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