Quantum criticality and tunable Griffiths phase in superconducting twisted trilayer graphene

Abstract When dimensionality is reduced, enhanced quantum fluctuations can destroy long-range phase coherence, driving a superconductor–insulator transition (SIT), where disorder and electronic correlations give rise to novel many-body states. Here, we report the first observation of a magnetic field–tuned SIT in mirror-symmetric twisted trilayer graphene (TTG). Remarkably, signatures of quantum criticality persist over an exceptionally broad range of magnetic fields and are well described by the formation of a quantum Griffiths phase, a regime in which rare spatially extended regions develop local order within a globally disordered phase. This leads to a quantum phase transition governed by an infinite-randomness fixed point and characterized by ultraslow relaxation dynamics. Near the quantum critical region, transport measurements reveal strongly nonlinear electrical behavior, including a current-driven reentrant transition from insulating to superconducting transport, providing direct evidence of local superconducting order. By tilting the magnetic field, we are able to collapse the broad Griffiths regime into a single quantum critical point (QCP), demonstrating a striking level of control over disorder-induced quantum dynamics. Our results further show that TTG strongly violates the Pauli limit and establishes twisted trilayer graphene as a tunable platform for exploring quantum phase fluctuations, Cooper pair localization, and unconventional superconductivity.