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# Special CAMP: Using 'noise' spectroscopy to understand ballistic, diffusive and localization-ridden dynamics in quantum many-body systems

## Main Content

Kartiek Agarwal, Harvard University
When
06 November 2015 from 4:00 PM to 5:00 PM
Where
339 Davey Laboratory
Contact Name
Jainendra Jain
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Noise is traditionally understood to be something of a nuisance: it leads to irregularities in the way our machines work, and it delays our ascendancy into the age of quantum computers. But noise is also an intrinsic property of the system, and by fluctuation-dissipation relations, it is tied to many useful linear-response properties of the system. The main aim of this talk is to highlight how spatially-resolved measurements of noise, especially magnetic noise, can non-invasively determine the complete form of the conductivity and polarizability of the underlying quantum system, thus, largely characterizing the dynamics of the system. I will focus on 3 particular systems of interest: 1) Disordered Heisenberg spin-networks [1,2]. I will discuss a novel real-space RG tool we recently developed to calculate magnetic noise from these systems; we show that these systems, under certain conditions, emit $1/f^\alpha$ noise, which is tied to both anomalous diffusion and many-body-localization in the system. 2) Intrinsic/Doped graphene [3]. I will discuss how magnetic fluctuations above the graphene sample can be measured by an NV center placed at varying distances. These distance-dependence of the noise will be of varying functional form depending on whether transport in the graphene sample is ballistic or diffusive. 3) Spin-orbit coupled 2DEGs [3]. Using similar ideas to that developed for graphene, I will discuss how the localization transition can be inferred from magnetic noise measurements.

[1] K. Agarwal et al., PRL 114, 160401 (2015)

[2] K. Agarwal et al.,ArXiv:1506.00643 (2015)

[3] K. Agarwal et al., in preparation.

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