Self-sustained current oscillations in spin-blockaded quantum dots

Hu, B. L.; Wang, Xiang Rong

doi:10.1103/physrevb.87.035311

Cited by 3 publications

(1 citation statement)

References 30 publications

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“…However, the explanation of the unstable region in figure 1(a) and the associated self-sustaining current oscillations may involve a nutation in the electron nuclear space and might necessitate the use of the density matrix approach [24,25]. This aspect still remains elusive with a couple of recently proposed candidates [26,27]. Developing an understanding of non-equilibrium situations that involve coupling with the dynamics of additional baths will form a new and important frontier in the area of nanoscale transport.…”

Section: Discussionmentioning

confidence: 99%

Role of dual nuclear baths on spin blockade leakage current bistabilities

Buddhiraju

Muralidharan²

2014

J. Phys.: Condens. Matter

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Spin-blockaded electronic transport across a double quantum dot (DQD) system represents an important advancement in the area of spin-based quantum information. The basic mechanism underlying the blockade is the formation of a blocking triplet state. The bistability of the leakage current as a function of the applied magnetic field in this regime is believed to arise from the effect of nuclear Overhauser fields on spin-flip transitions between the blocking triplet and the conducting singlet states. The objective of this paper is to present the nuances of considering a two bath model on the experimentally observed current bistability by employing a self consistent simulation of the nuclear spin dynamics coupled with the electronic transport of the DQD set up. In doing so, we first discuss the important subtleties involved in the microscopic derivation of the hyperfine mediated spin flip rates. We then give insights as to how the differences between the two nuclear baths and the resulting difference Overhauser field affect the two-electron states of the DQD and their connection with the experimentally observed current hysteresis curve.

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Section: Discussionmentioning

confidence: 99%

Role of dual nuclear baths on spin blockade leakage current bistabilities

Buddhiraju

Muralidharan²

2014

J. Phys.: Condens. Matter

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Limit-cycle phase in driven-dissipative spin systems

2015

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We explore the phase diagram of interacting spin-1/2 systems in the presence of anisotropic interactions, spontaneous decay and driving. We find a rich phase diagram featuring a limit cycle phase in which the magnetization oscillates in time. We analyze the spatio-temporal fluctuations of this limit cycle phase at the Gaussian level, and show that spatial fluctuations lead to quasi-long-range limit cycle ordering for dimension d = 2. This result can be interpreted in terms of a spatio-temporal Goldstone mode corresponding to phase fluctuations of the limit cycle. We also demonstrate that the limit-cycle phase exhibits an asymmetric power spectrum measurable in fluorescence experiments.PACS numbers: 75.10.Jm, 64.60.Ht A quantum system that is coherently driven and connected to a heat bath eventually reaches a steady state; when the system is macroscopic, this steady state can be ordered in the sense of spontaneously breaking a symmetry [1, 2]. The patterns of steady-state ordering are, in general, qualitatively different from those of the equilibrium phase diagrams: for instance, the interplay between coherent and dissipative dynamics can stabilize staggered phases that are absent in equilibrium [3], and by engineering the dissipative terms one can optically pump a many-body system into a pure state [4, 5]. The forms of steady-state order [6][7][8][9][10][11][12][13][14][15] that have been investigated to date mostly fit into equilibrium paradigms, such as the Landau paradigm of spontaneous symmetry breaking or the paradigm of topological order. However, the departure from equilibrium allows one to realize novel types of order-specifically, limit cycles (LC) [16][17][18][19][20] which break time-translation invariance-that have no obvious equilibrium counterpart. Although previous works have predicted a LC phase within mean-field theory [18][19][20], it is an open question whether such a phase really exists or is an artifact of mean-field theory.In this work, we show that the LC phase exists with long-range order in three and higher dimensions and quasi-long-range order in two dimensions. We study a paradigm model of interacting spins-the anisotropic spin-1/2 Heisenberg model in a transverse field-and find a regime where it exhibits a limit-cycle phase. We discuss the origin of the LC and study the effects of quantum fluctuations to go beyond previous mean-field works. We show by explicit, microscopic calculation that the spontaneous breaking of the continuous time-translation symmetry is reflected in the presence of a gapless "Goldstone" mode, and that this gapless mode prevents global timetranslation-symmetry-breaking in one or two dimensions. We then discuss this LC at a more phenomenological level, noting its unusual implications, e.g., that the temporal ordering of the LC phase gives rise to an asymmetric dynamical power spectrum of emitted photons. These predictions are straightforward to test in experiments with trapped ions [21][22][23] or Rydberg atoms [3,24,25].We want to contrast our paper with rec...

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Temperature-dependent dynamical nuclear polarization bistabilities in double quantum dots in the spin-blockade regime

et al. 2013

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The interplay of dynamical nuclear polarization (DNP) and leakage current through a double quantum dot in the spin-blockade regime is analyzed. A finite DNP is built up due to a competition between hyperfine (HF) spin-flip transitions and another inelastic escape mechanism from the triplets, which block transport. We focus on the temperature dependence of the DNP for zero energy-detuning (i.e. equal electrostatic energy of one electron in each dot and a singlet in the right dot). Our main result is the existence of a transition temperature, below which the DNP is bistable, so a hysteretic leakage current versus external magnetic field B appears. This is studied in two cases: (i) Close to the crossing of the three triplet energy levels near B = 0, where spin-blockade is lifted due to the inhomogeneity of the effective magnetic field from the nuclei. (ii) At higher B-fields, where the two spin-polarized triplets simultaneously cross two different singlet energy levels. We develop simplified models leading to different transition temperatures Tc,tt and Tc,st for the crossing of the triplet levels and the singlet-triplet level crossings, respectively. We find Tc,tt analytically to be given solely by the HF couplings, whereas Tc,st depends on various parameters and Tc,st > Tc,tt. The key idea behind the existence of the transition temperatures at zero energy-detuning is the suppression of energy absorption compared to emission in the inelastic HF transitions. Finally, by comparing the rate equation results with Monte Carlo simulations, we discuss the importance of having both HF interaction and another escape mechanism from the triplets to induce a finite DNP.

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Self-sustained current oscillations in spin-blockaded quantum dots

Cited by 3 publications

References 30 publications

Role of dual nuclear baths on spin blockade leakage current bistabilities

Role of dual nuclear baths on spin blockade leakage current bistabilities

Limit-cycle phase in driven-dissipative spin systems

Temperature-dependent dynamical nuclear polarization bistabilities in double quantum dots in the spin-blockade regime

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