Two-level states in glasses

Phillips, W. A.

doi:10.1088/0034-4885/50/12/003

Cited by 825 publications

(869 citation statements)

References 99 publications

(91 reference statements)

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“…Illuminating the resonator with optical photons, we observe a decrease in its resonance frequency and an increase in loss. We find that this photo-induced loss decreases with increasing rf drive, much as one expects for loss from coupling to an ensemble of TLSs 24 . However, we argue below that the power-dependent loss is actually due to the subtle behavior of nonequilibrium quasiparticles 13 .…”

Section: Introductionsupporting

confidence: 67%

“…However, photoabsorption could also remove TLSs from the bandwidth of the resonator, leading to reduced loss. Since the TLS asymmetry energy is expected to be uniformly distributed 24 , we would not expect photoabsorption to produce a net change in the number of active TLSs in the bandwidth of the resonator. Thus, the net effect of optical illumination should be to reduce the TLS loss.…”

Section: Loss From Two-level Systemsmentioning

confidence: 99%

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Effects of nonequilibrium quasiparticles in a thin-film superconducting microwave resonator under optical illumination

et al. 2016

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We have illuminated a thin-film superconducting Al lumped-element microwave resonator with 780 nm light and observed the resonator quality factor and resonance frequency as a function of illumination and microwave power in the 20 to 300 mK temperature range. The optically-induced microwave loss increases with increasing illumination but decreases with increasing microwave power. Although this behavior may suggest the presence of optically activated two-level systems, we find that the loss is better explained by the presence of nonequilibrium quasiparticles generated by the illumination and excited by the microwave drive. We model the system by assuming that the illumination creates an effective source of phonons with energy higher than double the superconducting gap and solve the coupled quasiparticle-phonon rate equations. We fit the simulation results to our measurements and find good agreement with the observed dependence of the resonator quality factor and frequency shift on temperature, microwave power, and optical illumination. Examination of the model reveals approaches to reducing optically-induced loss and improving the relaxation time of superconducting quantum devices.

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Section: Introductionsupporting

confidence: 67%

Section: Loss From Two-level Systemsmentioning

confidence: 99%

Effects of nonequilibrium quasiparticles in a thin-film superconducting microwave resonator under optical illumination

et al. 2016

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“…Δ can be calculated. A fluctuating Seebeck coefficient with a microscopic origin of fluctuating chemical potential due to two-level defects [36][37][38] in the etched nanostructures is reasonable in the context of an emerging pseudogap at low T. The pseudogap in these QW structures emerges over the same temperature range as the increase in voltage fluctuations, as T is reduced below 20 K. 18 The transfer of states away from the Fermi level during pseudogap formation and the resulting energy dependence of the density of states is both likely to enhance potential fluctuations due to defects and to enhance the Seebeck coefficient. An analogous response has been observed previously in germanium single crystals, where carrier density fluctuations result in a 1/f noise spectrum of the Seebeck coefficient, even without a dc current.…”

Section: Resultsmentioning

confidence: 99%

Potential Fluctuations at Low Temperatures in Mesoscopic-Scale SmTiO₃/SrTiO₃/SmTiO₃ Quantum Well Structures

et al. 2017

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Heterointerfaces of SrTiO 3 with other transition metal oxides make up an intriguing family of systems with a bounty of coexisting and competing physical orders. Some examples, such as LaAlO 3 /SrTiO 3 , support a high carrier density electron gas at the interface whose electronic properties are determined by a combination of lattice distortions, spin-orbit coupling, defects, and various regimes of magnetic and charge ordering. Here, we study electronic transport in mesoscale devices made with heterostructures of SrTiO 3 sandwiched between layers of SmTiO 3 , in which the transport properties can be tuned from a regime of Fermi-liquid like resistivity (ρ ∝ T 2 ) to a non-Fermi liquid (ρ ∝ T 5/3 ) by controlling the SrTiO 3 thickness. In mesoscale devices at low temperatures, we find unexpected voltage fluctuations that grow in magnitude as T is decreased below 20 K, are suppressed with increasing contact electrode size, and are independent of the drive current and contact spacing distance. Magnetoresistance fluctuations are also observed, which are reminiscent of universal conductance fluctuations but not entirely consistent with their conventional properties. Candidate explanations are considered, and a mechanism is suggested based on mesoscopic temporal fluctuations of the Seebeck coefficient.An improved understanding of charge transport in these model systems, especially their quantum coherent properties, may lead to insights into the nature of transport in strongly correlated materials that deviate from Fermi liquid theory. Interest in oxide-based heterostructures has intensified in recent years, in large part due to advances in epitaxial film growth and the discovery of a two-dimensional conductive interface between the insulating perovskite materials LaAlO 3 (LAO) and SrTiO 3 (STO). 1,2 The electron gas at this interface exhibits strong electronic correlations, resulting in competing orders that can be tuned by various external parameters (e.g., temperature, magnetic field, pressure, chemical doping, and electrostatic gating). [3][4][5][6][7][8] Techniques for growing high-quality films and atomically sharp interfaces of these transition metal oxides (TMOs) and their characterization are central to many ongoing research efforts. 9 The possibility for rich interplay between charge, spin, and orbital ordering makes oxide heterostructure systems excellent tools in the study of correlation phenomena with wide-ranging implications, from understanding high-T c superconductivity 10 to engineering materials with desirable functional properties. [11][12][13][14] Many aspects of these and related oxide heterostructures remain, however, only partially understood, including the nature of quantum coherence in transport, and relationship of coherence with other effects such as spinorbit coupling, localization (both weak and strong), and charge and magnetic ordering. KeywordsMotivating the present study is a body of prior work focused on quantum wells (QWs) in epitaxial STO layers sandwiched between layers of eit...

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“…Phenomenally, these two-level systems possess their dipole moments and thus can couple to the around electric fields. Consequently, the dielectric constant of the film could be modified, yielding the change of central resonant frequency [24][25][26]. With such a two-level system model, the temperature-dependent variation of the dielectric constant for the present resonator system can be expressed as [24] …”

Section: Irradiation Saturate Temperatures Of Superconducting Resonatmentioning

confidence: 99%

Microwave Resonators for Weak Light Detection at Telecom Wavelength

Zhou¹,

Wang²,

Wei³

et al. 2014

PIER

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Abstract-We report the experimental measurements of weak light signal at 1550 nm wavelength with a high-quality factor microwave coplanar waveguide (CPW) resonators. The quality factor of this niobium λ/4 CPW resonator is measured as Q = 7.4 × 10 5 at ultra-low temperature (20 mK). With this device, we developed a technique to implement the proper fiber-resonator coupling, and realized the desirable weak light detection at telecommunication wavelength with 35 pW resolution by probing the shift of resonance frequency (f 0 ). We found that the resonator shift increases with the increasing light power (from 11.7 pW to 9.77 nW), similar to the effects of increasing the system temperature (from 20 mK to 800 mK). The observed blue shifts of f 0 (with the increasing of either the temperature and the applied light powers) are thoroughly deviated from the usual Mattis-Bardeen theory prediction, and could be explained by the effects relating to the two-level system existed on surface of the CPW device.

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Two-level states in glasses

Cited by 825 publications

References 99 publications

Effects of nonequilibrium quasiparticles in a thin-film superconducting microwave resonator under optical illumination

Effects of nonequilibrium quasiparticles in a thin-film superconducting microwave resonator under optical illumination

Potential Fluctuations at Low Temperatures in Mesoscopic-Scale SmTiO₃/SrTiO₃/SmTiO₃ Quantum Well Structures

Microwave Resonators for Weak Light Detection at Telecom Wavelength

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Two-level states in glasses

Cited by 825 publications

References 99 publications

Effects of nonequilibrium quasiparticles in a thin-film superconducting microwave resonator under optical illumination

Effects of nonequilibrium quasiparticles in a thin-film superconducting microwave resonator under optical illumination

Potential Fluctuations at Low Temperatures in Mesoscopic-Scale SmTiO3/SrTiO3/SmTiO3 Quantum Well Structures

Microwave Resonators for Weak Light Detection at Telecom Wavelength

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Potential Fluctuations at Low Temperatures in Mesoscopic-Scale SmTiO₃/SrTiO₃/SmTiO₃ Quantum Well Structures