Title: Quantum Griffiths singularities in TiO superconducting thin films with insulating normal states

Abstract

A superconductor–metal transition (SMT) with an unconventional diverging dynamic critical exponent was recently discovered, and it drew tremendous attention because this signature of a quantum Griffiths singularity (QGS) was thought to be a common characteristic of low-disorder crystalline superconductors. However, because the QGS was observed only in limited materials with metallic normal states, the question of whether the QGS exists in other superconducting systems is still unanswered. In this paper, a superconductor–insulator transition (SIT) is observed in TiO thin films with insulating normal states, which offers a more universal platform for investigating the QGS. A thickness-tuned SIT is obtained when the magnetic field is zero. Importantly, a magnetic field-tuned SIT with a diverging dynamic critical exponent, which is direct evidence of a QGS, is observed in TiO thin films with different thicknesses. By constructing a comprehensive phase diagram, it is demonstrated that the critical magnetic fieldH_ctends to saturate as the temperature approaches 0 K, which is different from the upturn trend ofH_cobserved in SMT systems and probably due to the weaker Josephson coupling of the locally ordered superconducting islands (rare regions) in a weakly insulating normal state background. The results extend the QGS scenario from only SMT systems to SITmore » systems, and they provide vital evidence that QGSs are common in crystalline superconducting thin films, which has possible applications in quantum-computing devices.« less

Authors:

Zhang, Chao ^[1]; Fan, Yunjie ^[1]; Chen, Qiaoling ^[1]; Wang, Tianyi ^[2]; Liu, Xiang ^[1]; Li, Qi ^[3]; Yin, Yuewei  ^[1];

• Search DOE PAGES for author "Yin, Yuewei"
• Search DOE PAGES for ORCID "0000-0003-0965-4951"

Li, Xiaoguang ^[4]

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+ Show Author Affiliations

1. Univ. of Science and Technology of China, Hefei (China). Chinese Academy of Sciences (CAS), Key Lab. of Strongly-Coupled Quantum Matter Physics. Dept. of Physics. Hefei National Lab. for Physical Sciences at the Microscale
2. Univ. of Science and Technology of China, Hefei (China). Chinese Academy of Sciences (CAS), Key Lab. of Strongly-Coupled Quantum Matter Physics. Dept. of Physics. Hefei National Lab. for Physical Sciences at the Microscale; Pennsylvania State Univ., University Park, PA (United States). Dept. of Physics
3. Pennsylvania State Univ., University Park, PA (United States). Dept. of Physics
4. Univ. of Science and Technology of China, Hefei (China). Chinese Academy of Sciences (CAS), Key Lab. of Strongly-Coupled Quantum Matter Physics. Dept. of Physics. Hefei National Lab. for Physical Sciences at the Microscale. Inst. of Solid State Physics. Key Lab. of Materials Physics; Collaborative Innovation Center of Advanced Microstructures, Nanjing (China)

Publication Date:

Sun Dec 01 00:00:00 EST 2019

Research Org.:

Pennsylvania State Univ., University Park, PA (United States)

Sponsoring Org.:

USDOE Office of Science (SC)

OSTI Identifier:

1800582

Grant/Contract Number:  

FG02-08ER46531

Resource Type:

Accepted Manuscript

Journal Name:

NPG Asia Materials

Additional Journal Information:

Journal Volume: 11; Journal Issue: 1; Journal ID: ISSN 1884-4049

Publisher:

Nature Publishing Group Asia

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; Materials Science