We demonstrate the suppression of nuclear-spin fluctuations in an InAs quantum dot and measure the timescales of the spin narrowing effect. By initializing for tens of milliseconds with two continuous wave diode lasers, fluctuations of the nuclear spins are suppressed via the hole-assisted dynamic nuclear polarization feedback mechanism. The fluctuation narrowed state persists in the dark (abse...

The Jordan-Wigner transformation is known as a powerful tool in condensed matter theory, especially in the theory of low-dimensional quantum spin systems. The aim of this chapter is to review the application of the Jordan-Wigner fermionization technique for calculating dynamic quantities of low-dimensional quantum spin models. After a brief introduction of the Jordan-Wigner transformation for o...

Influence of spin fluctuations on the superconducting transition temperature and resistivity in the t − J model at large N Abstract Spin fluctuations enter the calculation of the superconducting transition temperature T c only in the next-to-leading order (i.e., in O(1/N 2) of the 1/N expansion of the t − J model. We have calculated these terms and show that they have only little influence on t...

General relations for nonequilibrium spin transport at a magnetic junction between normal metal and ferromagnetic insulator are derived from the quantum fluctuation theorem. They include extended Onsager conductance spin-current noise that hold states driven by an external current. These relations, valid general setup of Hall magnetoresistance, provide comprehensive viewpoint understanding unid...