Optical Spectroscopy of Spin Noise

Abstract

Spontaneous fluctuations of the magnetization of a spin system in thermodynamic equilibrium (spin noise) manifest themselves as noise in the Faraday rotation of probe light. We show that the correlation properties of this noise over the optical spectrum can provide clear information about the composition of the spin system that is largely inaccessible for conventional linear optics. Such optical spectroscopy of spin noise, e.g., allows us to clearly distinguish between optical transitions associated with different spin subsystems, to resolve optical transitions that are unresolvable in the usual optical spectra, to unambiguously distinguish between homogeneously and inhomogeneously broadened optical bands, and to evaluate the degree of inhomogeneous broadening. These new possibilities are illustrated by theoretical calculations and by experiments on paramagnets with different degrees of inhomogeneous broadening of optical transitions [atomic vapors of 41K and singly charged (In,Ga)As quantum dots].

Effect of the Pauli principle on photoelectron spin transport inp+GaAs

“…These phenomena are of interest in-and-of themselves and also because they may affect the operation of a large number of proposed semiconductor spintronic devices [1,[5][6][7]. Experimental investigations including the use of novel techniques such as spin gratings [8] or spin noise [9] reveal that these phenomena arise from one of two possible coupling mechanisms, either spin-charge or spin-spin couplings. In the former, the spin-orbit interaction plays a central role and gives rise to the extrinsic spin Hall effect and the spin helix, as well as providing the basis for the electrical manipulation of spin [10][11][12].…”

Squeezed-light spin noise spectroscopy

“…SNS has allowed measurement of g-factors, nuclear spin, isotope abundance ratios and relaxation rates of alkali atoms [5,6], g-factors, relaxation times and doping concentration of electrons in semiconductors [7][8][9][10][11] and localized holes in quantum dot ensembles [12,13] including single hole spin detection [14]. Recently, SNS has been used to study complex optical transitions and broadening processes [15,16], coherent phenomena beyond linear response [17] and cross-correlations of heterogeneous spin systems [18,19].…”

“…SNS has allowed measurement of g-factors, nuclear spin, isotope abundance ratios and relaxation rates of alkali atoms [5,6], g-factors, relaxation times and doping concentration of electrons in semiconductors [7][8][9][10][11] and localized holes in quantum dot ensembles [12,13] including single hole spin detection [14]. Recently, SNS has been used to study complex optical transitions and broadening processes [15,16], coherent phenomena beyond linear response [17] and cross-correlations of heterogeneous spin systems [18,19].Spin noise has been measured with nuclear magnetic resonance [20,21] and magnetic force microscopy [22][23][24], but the most sensitive and widely used detection technique is Faraday rotation (FR) [2,5,6], in which the spin noise is mapped onto the polarization of an off-resonant probe. In FR-SNS, spin noise near the Larmor frequency competes with quantum noise [25] of the detected photons, i.e., the optical shot noise.…”

Sensitivity, quantum limits, and quantum enhancement of noise spectroscopies

“…We illustrate and test the results using spin noise spectroscopy (SNS), a versatile technique that measures magnetic resonance features from thermal spin fluctations [18]. Non-optical SNS based on resonance force microscopy [19,20] and NV-center magnetometry [21][22][23] have recently emerged, but still the most widely used technique is optical Faraday rotation (FR) to detect spin orientation [24].…”

“…Understanding the statistical sensitivity of noise spectroscopy is essential for rigorous use of the technique in any of these fields. We study this problem from the perspective of parameter estimation theory, to derive the covariance matrix for spectral parameters obtained by fitting experimental spectra.We illustrate and test the results using spin noise spectroscopy (SNS), a versatile technique that measures magnetic resonance features from thermal spin fluctations [18]. Non-optical SNS based on resonance force microscopy [19,20] Quantum statistical fluctuations such as shot noise are often limiting in noise spectroscopies [6,27,34], making it important to understand quantum limits and techniques to overcome them.…”