Free at last: Bose metal uncaged

Phillips, Philip

doi:10.1126/science.aaz9902

Cited by 10 publications

(6 citation statements)

References 15 publications

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“…[123] Also as shown in Figure 4e, the observed h/2e quantum oscillations in nanopatterned YBCO thin films clearly demonstrate that the charge carriers are bosons. [121,124] The oscillation amplitude of conductance grows in the superconducting state, saturates in the metal, and decreases in the insulator as shown in Figure 4f, corresponding to a divergent phase coherent length in the superconductor, a finite size in the quantum metallic state, and no phase coherence in the insulator. Very recently, anomalous metallic state was also observed in MBE-grown PdTe 2 thin films under a perpendicular magnetic field; the detection was convincing since more than 99.999% of high-frequency noise power was reduced by the high-quality filter.…”

Section: Quantum Metallic Statementioning

confidence: 99%

Recent Advances in 2D Superconductors

et al. 2021

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The emergence of superconductivity in 2D materials has attracted much attention and there has been rapid development in recent years because of their fruitful physical properties, such as high transition temperature (Tc), continuous phase transition, and enhanced parallel critical magnetic field (Bc). Tremendous efforts have been devoted to exploring different physical parameters to figure out the mechanisms behind the unexpected superconductivity phenomena, including adjusting the thickness of samples, fabricating various heterostructures, tuning the carrier density by electric field and chemical doping, and so on. Here, different types of 2D superconductivity with their unique characteristics are introduced, including the conventional Bardeen–Cooper–Schrieffer superconductivity in ultrathin films, high‐Tc superconductivity in Fe‐based and Cu‐based 2D superconductors, unconventional superconductivity in newly discovered twist‐angle bilayer graphene, superconductivity with enhanced Bc, and topological superconductivity. A perspective toward this field is then proposed based on academic knowledge from the recently reported literature. The aim is to provide researchers with a clear and comprehensive understanding about the newly developed 2D superconductivity and promote the development of this field much further.

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Section: Quantum Metallic Statementioning

confidence: 99%

Recent Advances in 2D Superconductors

et al. 2021

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“…[146,147] The vanishing Hall resistance [136] and absence of cyclotron resonance [140,141] have suggested an emergent particle-hole symmetry in the anomalous metal state. In nanopatterned YBCO films, the observation of charge-2e quantum oscillations demonstrates the bosonic nature of the anomalous metal state, which is considered as solid evidence to end the long-standing debate on whether bosons can exist as a metal [172]. Multiple physical scenarios have been developed to describe the anomalous metal behavior, such as the Bose metal [129,173,174], the quantum fluctuation of superconducting order parameter [175][176][177], the coupling to dissipative heat bath [148,178,179], and the composite Fermi liquid [180].…”

Section: Mos 2 Nanoflakesmentioning

confidence: 99%

Quantum phase transitions in two-dimensional superconductors: a review on recent experimental progress

Wang,

Liu,

et al. 2023

Rep. Prog. Phys.

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Superconductor–insulator/metal transition (SMT) as a paradigm of quantum phase transition has been a research highlight over the last three decades. Benefit from recent developments in the fabrication and measurements of two-dimensional (2D) superconducting films and nanodevices, unprecedented quantum phenomena have been revealed in the quantum phase transitions of 2D superconductors. In this review, we introduce the recent progress on quantum phase transitions in 2D superconductors, focusing on the quantum Griffiths singularity (QGS) and anomalous metal state. Characterized by a divergent critical exponent when approaching zero temperature, QGS of SMT is discovered in ultrathin crystalline Ga films and subsequently detected in various 2D superconductors. The universality of QGS indicates the profound influence of quenched disorder on quantum phase transitions. Besides, in a 2D superconducting system, whether a metallic ground state can exist is a long-sought mystery. Early experimental studies indicate an intermediate metallic state in the quantum phase transition of 2D superconductors. Recently, in high-temperature superconducting films with patterned nanopores, a robust anomalous metal state (i.e. quantum metal or Bose metal) has been detected, featured as the saturated resistance in the low temperature regime. Moreover, the charge-2e quantum oscillations are observed in nanopatterned films, indicating the bosonic nature of the anomalous metal state and ending the debate on whether bosons can exist as a metal. The evidences of the anomalous metal states have also been reported in crystalline epitaxial thin films and exfoliated nanoflakes, as well as granular composite films. High quality filters are used in these works to exclude the influence of external high frequency noises in ultralow temperature measurements. The observations of QGS and metallic ground states in 2D superconductors not only reveal the prominent role of quantum fluctuations and dissipations but also provide new perspective to explore quantum phase transitions in superconducting systems.

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“…Even more interestingly, in recent times there have been reports of magnetic field induced 'Bose metal' state [162,[182][183][184][185][186], where the Cooper pairs are believed to be in a phase-incoherent dissipative state. However, there are debates on whether this is an intrinsic state of the system or one caused by the exposure of the fragile superconducting state to external electromagnetic radiation [187][188][189][190]. While detailed discussion of these rapidly evolving topics is beyond the purview of this article, before ending we would like to make one cautionary remark on the analysis of penetration depth data in magnetic field.…”

Section: Possible Role Of Phase Fluctuations In Other Two-dimensional...mentioning

confidence: 99%

Phase fluctuations in conventional superconductors

Raychaudhuri

Dutta

2021

J. Phys.: Condens. Matter

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Within the Bardeen–Cooper–Schrieffer (BCS) theory, superconductivity is entirely governed by the pairing energy scale, which gives rise to the superconducting energy gap, Δ. However, another important energy scale, the superfluid phase stiffness, J, which determines the resilience of the superconductor to phase-fluctuations is normally ignored. The spectacular success of BCS theory owes to the fact that in conventional superconductors J is normally several orders of magnitude larger than Δ and thus an irrelevant energy scale. However, in certain situations such as in the presence of low carrier density, strong disorder, at low-dimensions or in granular superconductors, J can drastically come down and even become smaller than Δ. In such situations, the temperature and magnetic field evolution of superconducting properties is governed by phase fluctuations, which gives rise to novel electronic states where signatures of electronic pairing continue to exist even when the zero resistance state is destroyed. In this article, we will review the recent experimental developments on the study of phase fluctuations in conventional superconductors.

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Free at last: Bose metal uncaged

Abstract: A Bose metallic phase disrupts the classic two-state superconductor-insulator picture. arXiv:1912.10051v1 [cond-mat.supr-con]

Cited by 10 publications

References 15 publications

Recent Advances in 2D Superconductors

Recent Advances in 2D Superconductors

Quantum phase transitions in two-dimensional superconductors: a review on recent experimental progress

Phase fluctuations in conventional superconductors

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