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Self-sustained oscillators (SSOs) is a commonly used method to generate classical clock signals and SSOs using delayed feedback have been developed commercially which possess ultra-low phase noise and drift. Research into the development of quantum self-oscillation, where one can also have a periodic and regular output tick , that can be used to control quantum and classical devices has received much interest and quantum SSOs so far studied suffer from phase diffusion which leads to the smearing out of the quantum oscillator over the entire limit cycle in phase space seriously degrading the system’s ability to perform as a self-oscillation. In this paper, we explore quantum versions of time-delayed SSOs, which has the potentials to develop a ticking quantum clock. We first design a linear quantum SSO which exhibits perfect oscillation without phase diffusion. We then explore a nonlinear delayed quantum SSO but find it exhibits dephasing similar to previously studied non-delayed systems.

Quantum oscillation (QO) measurements constitute a powerful method to measure the Fermi surface (FS) properties of metals. The observation of QOs is usually taken as strong evidence for the existence of extremal cross‐sectional areas of the FS according to the famous Onsager relation. Here, mechanisms that generate QO frequencies that defy the Onsager relation are reviewed and material candidates are discussed. These include magnetic breakdown, magnetic interaction, chemical potential oscillations, and Stark quantum interference, most of which lead to signals occurring at combinations of “parent” Onsager frequencies. A special emphasis is put on the recently discovered mechanism of quasi‐particle lifetime oscillations (QPLOs). This work aims to provide a field guide that allows, on the one hand, to distinguish such non‐Onsager QOs from conventional QOs arising from extremal cross sections and, on the other hand, to distinguish the various non‐Onsager mechanisms from each other. A practical classification of non‐Onsager QOs is given in terms of the prerequisites for their occurrence and their characteristics. It is shown that, in particular, the recently discovered QPLOs may pose significant challenges for the interpretation of QO spectra, as they may occur quite generically as frequency differences in multi‐orbit systems, without the necessity of visible “parent” frequencies in the spectrum, owing to a strongly suppressed temperature dephasing of QPLOs. An extensive list of material candidates is presented where QPLOs may represent an alternative explanation for the observation of unexpected QO frequencies. The observation of quantum oscillations is usually taken as strong evidence for the existence of a Fermi surface according to the famous Onsager relation. The article reviews mechanisms that generate quantum oscillation frequencies that defy the Onsager relation where special emphasis is put on the recently discovered quasi‐particle lifetime oscillations. An extensive list of material candidates is presented.

A central question in the underdoped cuprates pertains to the nature of the pseudogap ground state. A conventional metallic ground state of the pseudogap region has been argued to host quantum oscillations upon destruction of the superconducting order parameter by modest magnetic fields. Here, we use low applied measurement currents and millikelvin temperatures on ultrapure single crystals of underdoped YBa₂Cu₃O6+x to unearth an unconventional quantum vortex matter ground state characterized by vanishing electrical resistivity, magnetic hysteresis, and nonohmic electrical transport characteristics beyond the highest laboratory-accessible static fields. A model of the pseudogap ground state is now required to explain quantum oscillations that are hosted by the bulk quantum vortex matter state without experiencing sizable additional damping in the presence of a large maximum superconducting gap; possibilities include a pair density wave.

SignificanceTopological materials exhibit a nontrivial Berry phase, experimental determination of which heavily relies on a straightforward phase analysis of quantum oscillations. We report the observation of a striking spin-zero effect in quantum oscillations of topological materials. The concomitant phase inversion underlines a largely overlooked phase factor in previous oscillation analysis of topological materials. Moreover, our results indicate that the Berry phase in ZrTe5 remains nontrivial in the presence of a magnetic field and support a field-driven line node phase. One of the characteristics of topological materials is their nontrivial Berry phase. Experimental determination of this phase largely relies on a phase analysis of quantum oscillations. We study the angular dependence of the oscillations in a Dirac material ZrTe5 and observe a striking spin-zero effect (i.e., vanishing oscillations accompanied with a phase inversion). This indicates that the Berry phase in ZrTe5 remains nontrivial for arbitrary field direction, in contrast with previous reports. The Zeeman splitting is found to be proportional to the magnetic field based on the condition for the spin-zero effect in a Dirac band. Moreover, it is suggested that the Dirac band in ZrTe5 is likely transformed into a line node other than Weyl points for the field directions at which the spin zero occurs. The results underline a largely overlooked spin factor when determining the Berry phase from quantum oscillations.

The observation of 1/B-periodic behavior in Kondo insulators and semiconductor quantum wells challenges the conventional wisdom that quantum oscillations (QOs) necessarily arise from Fermi surfaces in metals.We revisit recently proposed theories for this phenomenon, focusing on a minimal model of an insulator with a hybridization gap between two opposite-parity light and heavy mass bands with an inverted band structure.We show that there are characteristic differences between the QO frequencies in the magnetization and the low-energy density of states (LE-DOS) of these insulators, in marked contrast to metals where all observables exhibit oscillations at the same frequency. The magnetization oscillations arising from occupied Landau levels occur at the same frequency that would exist in the unhybridized case.The LE-DOS oscillations in a disorder-free system are dominated by gap-edge states and exhibit a beat pattern between two distinct frequencies at low temperature. Disorder-induced in-gap states lead to an additional contribution to the DOS at the unhybridized frequency. The temperature dependence of the amplitude and phase of the magnetization and DOS oscillations are also qualitatively different and show marked deviations fromthe Lifshitz—Kosevich form well known inmetals.We also compute transport to ensure that we are probing a regime with insulating upturns in the direct current (DC) resistivity.

There has been growing speculation that a pair density wave state is a key component of the phenomenology of the pseudogap phase in the cuprates. Recently, direct evidence for such a state has emerged from an analysis of scanning tunneling microscopy data in halos around the vortex cores. By extrapolation, these vortex halos would then overlap at a magnetic-field scale where quantum oscillations have been observed. Here, we show that a biaxial pair density wave state gives a unique description of the quantum oscillation data, bolstering the case that the pseudogap phase in the cuprates may be a pair density wave state.

Whereas the discovery of Dirac- and Weyl-type excitations in electronic systems is a major breakthrough in recent condensed matter physics, finding appropriate materials for fundamental physics and technological applications is an experimental challenge. In all of the reported materials, linear dispersion survives only up to a few hundred millielectronvolts from the Dirac or Weyl nodes. On the other hand, real materials are subject to uncontrolled doping during preparation and thermal effect near room temperature can hinder the rich physics. In ZrSiS, angle-resolved photoemission spectroscopy measurements have shown an unusually robust linear dispersion (up to ∼2 eV) with multiple nondegenerate Dirac nodes. In this context, we present the magnetotransport study on ZrSiS crystal, which represents a large family of materials (WHM with W = Zr, Hf; H = Si, Ge, Sn; M = O, S, Se, Te) with identical band topology. Along with extremely large and nonsaturating magnetoresistance (MR), ∼1.4 × 10⁵% at 2 K and 9 T, it shows strong anisotropy, depending on the direction of the magnetic field. Quantum oscillation and Hall effect measurements have revealed large hole and small electron Fermi pockets. A nontrivial π Berry phase confirms the Dirac fermionic nature for both types of charge carriers. The long-sought relativistic phenomenon of massless Dirac fermions, known as the Adler–Bell–Jackiw chiral anomaly, has also been observed.

The security of digital information is one of the most unavoidable issue in current digital world. The existing world facing number of digital information breaches due to weak utilization of confidentiality preserving techniques. In this article, we have designed a new mechanism for the security of secret digital information for instance digital images. The proposed image encryption scheme is based on quantum harmonic oscillator and Schrodinger paradox. Moreover, suggested technique is further authenticated by utilizing security performance analysis and compared the obtained results with existing benchmarks schemes.

The magnetotransport behavior inside the nematic phase of bulk FeSe reveals unusual multiband effects that cannot be reconciled with a simple two-band approximation proposed by surface-sensitive spectroscopic probes. In order to understand the role played by the multiband electronic structure and the degree of two-dimensionality, we have investigated the electronic properties of exfoliated flakes of FeSe by reducing their thickness. Based on magnetotransport and Hall resistivity measurements, we assess the mobility spectrum that suggests an unusual asymmetry between the mobilities of the electrons and holes, with the electron carriers becoming localized inside the nematic phase. Quantum oscillations in magnetic fields up to 38 T indicate the presence of a hole-like quasiparticle with a lighter effective mass and a quantum scattering time three times shorter, as compared with bulk FeSe.The observed localization of negative charge carriers by reducing dimensionality can be driven by orbitally dependent correlation effects, enhanced interband spin fluctuations, or a Lifshitz-like transition, which affect mainly the electron bands. The electronic localization leads to a fragile two-dimensional superconductivity in thin flakes of FeSe, in contrast to the two-dimensional high-T c induced with electron doping via dosing or using a suitable interface.

An enduring question in correlated systems concerns whether superconductivity is favored at a quantum critical point (QCP) characterized by a divergent quasiparticle effective mass. Despite such a scenario being widely postulated in high Tc cuprates and invoked to explain non-Fermi liquid transport signatures, experimental evidence is lacking for a critical divergence under the superconducting dome. We use ultrastrong magnetic fields to measure quantum oscillations in underdoped YBa₂Cu₃O₆₊x, revealing a dramatic doping-dependent upturn in quasiparticle effective mass at a critical metal-insulator transition beneath the superconducting dome. Given the location of this QCP under a plateau in Tc in addition to a postulated QCP at optimal doping, we discuss the intriguing possibility of two intersecting superconducting subdomes, each centered at a critical Fermi surface instability.