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arXiv:2502.04439

Quantum noise spectroscopy of superconducting dynamics in a cuprate thin film

Zhongyuan Liu, Ruotian Gong, Jaewon Kim, Oriana K. Diessel, Jiajie Cheng, Qiaozhi Xu, Zackary Rehfuss, Xinyi Du, Guanghui He, Abhishek Singh, Yun Suk Eo, Erik A. Henriksen, G. D. Gu, Norman Y. Yao, Francisco Machado, Sheng Ran, Shubhayu Chatterjee, Chong Zu

Published Feb 6, 2025• 1 citation
arXivHTMLPDF

Abstract

Characterizing the low-energy dynamics of quantum materials is crucial for understanding strongly correlated electronic states, yet remains experimentally challenging, particularly in two-dimensional systems. Here, we leverage nitrogen-vacancy (NV) centers in diamond as a non-invasive quantum sensor to study thin-film Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$ (BSCCO), revealing several distinct dynamical phenomena across the superconducting phase diagram. At zero magnetic field and low temperatures, NV depolarization ($T_1$) spectroscopy captures GHz-scale noise from nodal quasiparticle excitations, consistent with Bardeen--Cooper--Schrieffer (BCS) mean-field theory. Near the critical temperature $T_c \approx 90$ K, supercurrent-fluctuation-induced noise sharply reduces $T_1$. By analyzing the temperature scaling of $T_1$, we observe clear deviations from mean-field prediction, reflecting the importance of order parameter fluctuations and enabling the determination of critical exponents. Under a small magnetic field, a broad and asymmetric reduction of $T_1$ unveils a liquid-like phase of mobile vortices. NV decoherence ($T_2$) spectroscopy further probes MHz-scale noise and reveals complex vortex-solid fluctuations well below $T_c$. Our results establish quantum noise spectroscopy as a non-invasive probe of superconducting dynamics over frequency and length scales complementary to existing techniques.

DOI
10.48550/arxiv.2502.04439

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The transition between distinct phases of matter is characterized by the nature of fluctuations near the critical point. We demonstrate that noise spectroscopy can not only diagnose the presence of a phase transition, but can also determine fundamental properties of its criticality. In particular, by analyzing a scaling collapse of the decoherence profile, one can directly extract the critical exponents of the transition and identify its universality class. Our approach naturally captures the presence of conservation laws and distinguishes between classical and quantum phase transitions. In the context of quantum magnetism, our proposal complements existing techniques and provides a novel toolset optimized for interrogating two-dimensional magnetic materials.
Abstract Critical parameters are the key to superconductivity research, and reliable instrumentations can facilitate the study. Traditionally, one has to use several different measurement techniques to measure critical parameters separately. In this work, we develop the use of a single species of quantum sensor to determine and estimate several critical parameters with the help of independent simulation data. We utilize the nitrogen-vacancy (NV) center in the diamond, which recently emerged as a promising candidate for probing exotic features in condensed matter physics. The non-invasive and highly stable nature provides extraordinary opportunities to solve scientific problems in various systems. Using a high-quality single-crystalline YBa2Cu4O8 (YBCO) as a platform, we demonstrate the use of diamond particles and a bulk diamond to probe the Meissner effect. The evolution of the vector magnetic field, the H − T phase diagram, and the map of fluorescence contour are studied via NV sensing. Our results reveal different critical parameters, including lower critical field H c 1 , upper critical field H c 2 , and critical current density j c , as well as verifying the unconventional nature of this high-temperature superconductor YBCO. Therefore, NV-based quantum sensing techniques have huge potential in condensed matter research.