Abstract
Recent transport experiments in spatially modulated quasi-1D structures created on top of LaAlO_33/SrTiO_33 interfaces have revealed some interesting features, including phenomena conspicuously absent without the modulation. In this work, we focus on two of these remarkable features and provide theoretical analysis allowing their interpretation. The first one is the appearance of two-terminal conductance plateaus at rational fractions of e^2/he2/h. We explain how this phenomenon, previously believed to be possible only in systems with strong repulsive interactions, can be stabilized in a system with attraction in the presence of the modulation. Using our theoretical framework we find the plateau amplitude and shape, and characterize the correlated phase which develops in the system due to the partial gap, namely a Luttinger liquid of electronic trions. The second observation is a sharp conductance dip below a conductance of 1\times e^2/h1×e2/h, which changes its value over a wide range when tuning the system. We theorize that it is due to resonant backscattering caused by a periodic spin-orbit field. The behavior of this dip can be reliably accounted for by considering the finite length of the electronic waveguides, as well as the interactions therein. The phenomena discussed in this work exemplify the intricate interplay of strong interactions and spatial modulations, and reveal the potential for novel strongly correlated phases of matter in systems which prominently feature both.
Highlights
Low dimensional electronic systems with strong interactions present unique opportunities for the implementation and study of highly correlated quantum matter
Recent experiments in these quasi-1D structures have explored the introduction of an additional feature, namely spatially periodic modulation of the waveguide. This may be done in a “vertical” way, i.e., by modulating the voltage applied by the atomic force microscopy (AFM) tip during the patterning of the wire, which creates an effective Kronig–Penney landscape for the electrons [19]
It is worth pointing out that the expressions we have found for the Luttinger parameters [see Eq (18)], and their dependence on the interaction matrix elements are correct only for weak coupling, i.e., when the typical bandwidth of the two modes W is sufficiently larger than the size of the elements comprising the interaction matrix U
Summary
Low dimensional electronic systems with strong interactions present unique opportunities for the implementation and study of highly correlated quantum matter. Electric conductance experiments in these heterostructures have revealed ballistic transport, and apparent strong attractive interactions between the charge carriers which lead to formation of composite few-electron particles [17, 18]. Recent experiments in these quasi-1D structures have explored the introduction of an additional feature, namely spatially periodic modulation of the waveguide. Transport measurements in the vertical case have revealed a regime in which a plateau in the two-terminal conductance appears at rational fractions of the quantum of conductance [19] Such phenomena have been previously observed in 1D constrictions [21], yet it was commonly believed strong repulsion is needed to stabilize the fractional phase [22]. We explain how this feature can be used as a powerful probe on the strength of the interactions in the system
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