Noninvasive probes of charge fractionalization in quantum spin Hall insulators

We examine dissipation effects in a multichannel quantum RC circuit, comprising a cavity or single-electron box capacitively coupled to a gate and connected to a reservoir lead via several conducting channels. Depending on the engineering details of the quantum RC circuit, the number of channels contributing to transport varies, as does the form of the interchannel couplings. For low-frequency AC transport, the charge-relaxation resistance (Rq) is a nontrivial function of the parameters of the system. However, in the vicinity of the charge degeneracy points and for weak tunneling, we find as a result of cross-mode mixing or channel asymmetry that Rq becomes universal for a metallic cavity at low temperatures, and equals the unit of quantum resistance. To prove this universality we map the system to an effective one-channel Kondo model, and construct an analogy with the Coulomb gas. Next, we probe the opposite regime of near-perfect transmission using a bosonization approach. Focussing on the two-channel case, we study the effect of backscattering at the lead-dot interface, more specifically, the role of an asymmetry in the backscattering amplitudes, and make a connection with the weak tunneling regime near the charge degeneracy points.

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“…(35). In terms of the new fermionic fields ψ s (x) and the "slave" fermion d, the kinetic part of the spin Hamiltonian becomes…”

Section: B Weak Backscattering and 2-channel Kondo Physicsmentioning

confidence: 99%

Strongly correlated dynamics in multichannel quantum RC circuits

et al. 2013

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“…An upper bound is given by the inelastic mean free path l in . Ballistic transport has been observed up to a few-micrometer-long samples, but further comprehension of the scattering mechanisms [50,51] would allow one to increase the coherence length up to tens of micrometers [34,[52][53][54][55][56][57]. The plot of Fig.…”

Section: Injmentioning

confidence: 99%

“…Our proposal is based on the edge states of two-dimensional (2D) topological insulators [21][22][23], whose properties are described in terms of counterpropagating channels characterized by spin-momentum locking. In the presence of interactions, these are described as helical Luttinger liquids (hLL) [24][25][26][27][28][29][30][31][32][33][34], whose first experimental manifestations have been recently observed [35]. Here, charge and spin sectors are connected and the presence of interactions implies the simultaneous fractionalization of both degrees of freedom [30,36].…”

Section: Introductionmentioning

confidence: 99%

Time-resolved pure spin fractionalization and spin-charge separation in helical Luttinger liquid based devices

et al. 2015

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Helical Luttinger liquids, appearing at the edge of two-dimensional topological insulators, represent a new paradigm of one-dimensional systems, where peculiar quantum phenomena can be investigated. Motivated by recent experiments on charge fractionalization, we propose a setup based on helical Luttinger liquids that allows one to time-resolve, in addition to charge fractionalization, also spin-charge separation and pure spin fractionalization. This is due to the combined presence of spin-momentum locking and interactions. We show that electric time-resolved measurements can reveal both charge and spin properties, avoiding the need of magnetic materials. Although challenging, the proposed setup could be achieved with present-day technologies, promoting helical liquids as interesting playgrounds to explore the effects of interactions in one dimension.

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“…The celebrated Fermi liquid theory dramatically fails and intriguing phenomena appear, such as the fractionalization of the charge [3][4][5][6][7] and the spin [7][8][9][10][11] degrees of freedom. Here, an electron injected into an interacting system splits up, originating two collective excitations that carry a fraction of the electron charge and spin.…”

Section: Introductionmentioning

confidence: 99%

Time-resolved energy dynamics after single electron injection into an interacting helical liquid

et al. 2016

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The possibility of injecting a single electron into ballistic conductors is at the basis of the new field of electron quantum optics. Here, we consider a single electron injection into the helical edge channels of a topological insulator. Their counterpropagating nature and the unavoidable presence of electron-electron interactions dramatically affect the time evolution of the single wave packet. Modeling the injection process from a mesoscopic capacitor in the presence of nonlocal tunneling, we focus on the time-resolved charge and energy packet dynamics. Both quantities split up into counterpropagating contributions whose profiles are strongly affected by the interaction strength. In addition, stronger signatures are found for the injected energy, which is also affected by the finite width of the tunneling region, in contrast to what happens for the charge. Indeed, the energy flow can be controlled by tuning the injection parameters, and we demonstrate that, in the presence of nonlocal tunneling, it is possible to achieve a situation in which charge and energy flow in opposite directions.

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Noninvasive probes of charge fractionalization in quantum spin Hall insulators

Cited by 17 publications

References 41 publications

Strongly correlated dynamics in multichannel quantum RC circuits

Strongly correlated dynamics in multichannel quantum RC circuits

Time-resolved pure spin fractionalization and spin-charge separation in helical Luttinger liquid based devices

Time-resolved energy dynamics after single electron injection into an interacting helical liquid

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