What is a spin glass? A glimpse via mesoscopic noise

Weissman, M. B.

doi:10.1103/revmodphys.65.829

Cited by 150 publications

(161 citation statements)

References 34 publications

Supporting

Mentioning

148

Contrasting

Unclassified

Order By: Relevance

“…Usually 1/f noise is associated with the onset of a spinglass phase as is believed to account for the many anomalous properties of spin-glasses at low temperatures [10,11]. However recent Monte-Carlo simulations by Chen and Yu [12] have ruled out this out to explain magnetization noise in SQUIDs.…”

Section: Clusters Of Interacting Two-level-systems (Tls)likely Due To Fmentioning

confidence: 99%

“…Since inductance is even under time inversion and flux is odd, their three-point crosscorrelation function must vanish unless time reversal symmetry is broken, which indicates the appearance of long range magnetic order. As this further implies that the mechanism producing both the flux-and inductance noise is the same, it is not clear on why only the associated spectrum (inductance noise) should have a large temperature dependence [5].Usually 1/f noise is associated with the onset of a spinglass phase as is believed to account for the many anomalous properties of spin-glasses at low temperatures [10,11]. However recent Monte-Carlo simulations by Chen and Yu [12] have ruled out this out to explain magnetization noise in SQUIDs.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Ising-Glauber Spin Cluster Model for Temperature-Dependent Magnetization Noise in SQUIDs

2014

Phys. Rev. Lett.

View full text Add to dashboard Cite

Clusters of interacting two-level-systems (TLS),likely due to F+ centers at the metal-insulator interface, are shown to self consistently lead to 1/f α magnetization noise in SQUIDs. By introducing a correlation-function calculation method and without any a priori assumptions on the distribution of fluctuation rates, it is shown why the flux noise is only weakly temperature dependent with α < ∼ 1, while the inductance noise has a huge temperature dependence seen in experiment, even though the mechanism producing both spectra is the same. Though both ferromagnetic-RKKY and short-range-interactions (SRI) lead to strong flux-inductance-noise cross-correlations seen in experiment, the flux noise varies a lot with temperature for SRI. Hence it is unlikely that the TLS's time reversal symmetry is broken by the same mechanism which mediates surface ferromagnetism in nanoparticles and thin films of the same insulator materials. PACS numbers: 85.25.Dq, 03.67.Lx Superconducting quantum interference devices (SQUID) are of considerable interest for quantum information as they can replicate natural qubits, such as electron and nuclear spins, using macroscopic devices. However the performance of superconducting qubits is severely impeded by the presence of 1/f magnetization noise which limits their quantum coherence. This type of noise was first observed in SQUIDs well over two decades ago [1,2], however its origins and many of its features remain unexplained. Recent activity in quantum computing has however revived interests to better understand this magnetization noise. [3,4].Magnetic noise in SQUIDs has several puzzling features. While the flux noise (the first spectrum) is also weakly dependent on temperature, the choice of the superconducting material and the SQUID's area [1,5,6] -the inductance noise (the second spectrum or the noise of the flux noise), surprisingly shows a strong temperature dependence. It decreases with increasing temperature and scales as 1/f α [5] where the temperature dependent (0 < α(T ) < 1) [7]. The flux noise is also known to be only weakly dependent on geometry and the noise scales as l/w, in the limit w/l << 1 (l is the length and w is the width of the superconducting wire) [8]. This along with recent experiments [5] suggests that flux noise arises from unpaired surface spins which reside at the Experimental evidence also suggests that these surface spins are strongly interacting and that there is a net spin polarization [5] as the 1/f inductance noise is highly correlated with the usual 1/f flux noise. This cross-correlation is inversely proportional to the temperature and is about the order of unity roughly below 100mK. Since inductance is even under time inversion and flux is odd, their three-point crosscorrelation function must vanish unless time reversal symmetry is broken, which indicates the appearance of long range magnetic order. As this further implies that the mechanism producing both the flux-and inductance noise is the same, it is not clear on why only the associated spectrum ...

show abstract

Section: Clusters Of Interacting Two-level-systems (Tls)likely Due To Fmentioning

confidence: 99%

mentioning

confidence: 99%

Ising-Glauber Spin Cluster Model for Temperature-Dependent Magnetization Noise in SQUIDs

2014

Phys. Rev. Lett.

View full text Add to dashboard Cite

show abstract

“…1(b)]. In addition, we have also analyzed the so-called second spectrum S 2 (f 2 , f ), which is the power spectrum of the fluctuations of S R (f ) with time [16]. S 2 (f 2 , f ) provides a direct probe of correlations between fluctuators: it is white (independent of f 2 ) for uncorrelated, and S 2 ∝ 1/f 1−β 2 for interacting fluctuators [16].…”

Section: Fig 1: (A)∆r(t)/ Rmentioning

confidence: 99%

“…In addition, we have also analyzed the so-called second spectrum S 2 (f 2 , f ), which is the power spectrum of the fluctuations of S R (f ) with time [16]. S 2 (f 2 , f ) provides a direct probe of correlations between fluctuators: it is white (independent of f 2 ) for uncorrelated, and S 2 ∝ 1/f 1−β 2 for interacting fluctuators [16]. At B = 0, the glass transition in Si MOSFETs was manifested by a sudden and dramatic increase of S R , a rapid rise of α from ≈ 1 to ≈ 1.8 [2,3], and a change of the exponent (1 − β) from a white (zero) to a nonwhite (nonzero) value [3].…”

Section: Fig 1: (A)∆r(t)/ Rmentioning

confidence: 99%

Glassy behavior of a two-dimensional electron system in Si in parallel magnetic fields

2004

View full text Add to dashboard Cite

Studies of low-frequency resistance noise show that the glassy freezing of the two-dimensional electron system (2DES) in Si in the vicinity of the metal-insulator transition (MIT) persists in parallel magnetic fields B of up to 9 T. At low B, both the glass transition density ng and nc, the critical density for the MIT, increase with B such that the width of the metallic glass phase (nc < ns < ng) increases with B. At higher B, where the 2DES is spin polarized, nc and ng no longer depend on B. Our results demonstrate that charge, as opposed to spin, degrees of freedom are responsible for glassy ordering of the 2DES near the MIT.PACS numbers: 71.30.+h, 71.27.+a, 73.40.Qv The fascinating strong correlation physics exhibited by low-density two-dimensional (2D) electron and hole systems [1] remains the subject of intensive research. In the vicinity of the apparent metal-insulator transition (MIT), in particular, both electron-electron interactions and disorder appear to be equally important. [2,3] are consistent with the model of glassy behavior that occurs in the charge sector [5,8,9], it is still an open question whether charge or spin degrees of freedom are responsible for the observed glass transition. Since a sufficiently strong magnetic field is expected to destroy the spin glass order [7,10], experimental studies of glassy dynamics in parallel magnetic fields B [11] should be able to distinguish between the proposed models. Here we present such a study, which shows that the glass transition persists even in B such that the 2D system is spin polarized. These results demonstrate that charge, as opposed to spin, degrees of freedom are responsible for glassy ordering of the 2DES near the MIT.Previous studies carried out at B = 0 employed a combination of transport and low-frequency resistance noise measurements [2,3] to probe the glassy behavior. The glass transition was manifested by a sudden and dramatic slowing down of the electron dynamics and by an abrupt change to the sort of statistics characteristic of complicated multistate systems, consistent with the hierarchical picture of glassy dynamics. It was also found [2] that the glass transition occurs in the metallic phase, i.e. at an electron density n g > n c , where n c is the critical density for the MIT determined from the vanishing of activation energy in the insulating regime [12,13]. The intermediate metallic glass (MG) phase is of considerable width in strongly disordered samples ((n g − n c )/n c ≈ 0.5 [2]), whereas in devices with low disorder n g is only a few percent higher than n c [3], in agreement with theory [9]. In this work, we investigate the glass transition in these same high peak mobility (low disorder) devices using noise spectroscopy in a parallel B. We find that all the signatures of the glass transition in parallel B are qualitatively the same as in B = 0, even when the electrons are spin polarized at high B. We construct a phase diagram in the (n s , B) plane (n s is the electron density), and find that the MG phase is broadene...

show abstract

“…Replica symmetry breaking [1] and droplet theory [2,3] constitute two pictures that were already available in the 80's. It is a debated question to determine which of these two visions of the problem does apply to laboratory experiments (see for instance [4]). Recent "memory and chaos" experiments [5] suggest that a new type of droplet theory is needed but there exists unsolved questions that have been the subject of recent works (see for instance [6,7]).…”

Section: Introductionmentioning

confidence: 99%

Slow relaxation experiments in disordered charge and spin density waves: collective dynamics of randomly distributed solitons

Mélin¹,

Biljaković

Lasjaunias³

et al. 2002

Eur. Phys. J. B

View full text Add to dashboard Cite

We show that the dynamics of disordered charge density waves (CDWs) and spin density waves (SDWs) is a collective phenomenon. The very low temperature specific heat relaxation experiments are characterized by: (i) "interrupted" ageing (meaning that there is a maximal relaxation time); and (ii) a broad power-law spectrum of relaxation times which is the signature of a collective phenomenon. We propose a random energy model that can reproduce these two observations and from which it is possible to obtain an estimate of the glass cross-over temperature (typically Tg ≃ 100 − 200 mK). The broad relaxation time spectrum can also be obtained from the solutions of two microscopic models involving randomly distributed solitons. The collective behavior is similar to domain growth dynamics in the presence of disorder and can be described by the dynamical renormalization group that was proposed recently for the one dimensional random field Ising model [D.S. Fisher, P. Le Doussal and C. Monthus, Phys. Rev. Lett. 80, 3539 (1998)]. The typical relaxation time scales like τ typ ∼ τ0 exp (Tg/T ). The glass cross-over temperature Tg related to correlations among solitons is equal to the average energy barrier and scales like Tg ∼ 2xξ0∆. x is the concentration of defects, ξ0 the correlation length of the CDW or SDW and ∆ the charge or spin gap.

show abstract

What is a spin glass? A glimpse via mesoscopic noise

Cited by 150 publications

References 34 publications

Ising-Glauber Spin Cluster Model for Temperature-Dependent Magnetization Noise in SQUIDs

Ising-Glauber Spin Cluster Model for Temperature-Dependent Magnetization Noise in SQUIDs

Glassy behavior of a two-dimensional electron system in Si in parallel magnetic fields

Slow relaxation experiments in disordered charge and spin density waves: collective dynamics of randomly distributed solitons

Contact Info

Product

Resources

About