Multi-terminal ballistic transport in one-dimensional wires

Abstract

Recent experiments (Yacoby et al., Phys. Rev. Lett. 77 (1996) 4612; Solid State Commun. 101 (1997) 77; M. Rother et al., ICPS-24, Th-P137) have shown non-universal conductance quantization in one-dimensional wires that are fabricated using the cleaved edge overgrowth technique (L.N. Pfei er et al., Microelectronics J. 28 (1997) 817). In one of the papers (Yacoby et al., Phys. Rev. Lett. 77 (1996) 4612), it was speculated that the origin of the reduced conductance lies in the interface between the one-dimensional wire and the two-dimensional electron gas regions, which serve as ohmic contacts and thermal reservoirs. Here we report the results of a systematic study of such 2D-1D interfaces. By embedding a 2D-1D interaction section region of controllable length inside an otherwise isolated wire, we were able to study the properties of the coupling between these two subsystems. Our results show that 2D-1D interface is in fact the origin of the non-universal conductance. ? 2000 Elsevier Science B.V. All rights reserved. One-dimensional electronic systems, the so-called Luttinger-liquids, are expected to show unique transport properties as a consequence of the Coulomb interaction between carriers [1][2][3][4][5][6][7]. In contrast to Fermi liquid theory [8][9][10][11][12], the Luttinger model predicts that even the weakest impurity embedded in an otherwise perfectly clean 1D wire will completely suppress its conductance at zero temperature. Furthermore, the tunneling conductance into such a perfect wire will also be completely suppressed at zero temperature. * Corresponding author.One of the ÿngerprints of a clean non-interacting 1D conductor is its quantized conductance in multiples of the universal value g 0 = 2e 2 =h. This quantization results from an exact cancellation of the increasing electron velocity and the decreasing density of states as the carrier density increases [13][14][15][16]. Therefore, as subsequent 1D electronic subbands are ÿlled with electrons the conductance increases in a series of plateaus (or steps) with values equal to g 0 multiplied by the number of occupied wire modes. Surprisingly, the inclusion of interactions does not alter this prediction. Early papers [4 -7], considering inÿnitely long wires, did in fact predict quantization 1386-9477/00/$ -see front matter ? 2000 Elsevier Science B.V. All rights reserved. PII: S 1 3 8 6 -9 4 7 7 ( 9 9 ) 0 0 0 9 7 -1

Quantized conductance and intersubband scattering in serially connected quantum wires

“…The higher QWR subbands do not exhibit such resistance, showing that they are much better coupled to the 2DEG. These observations are also consistent with recently published results in T-shaped QWRs [13,14].…”

“…We believe though, that electronphonon interaction could be excluded, due to the low measurement temperature relative to the Debye temperature. It should also be noted that in T-shaped QWRs with much stronger CP [13,14], the deviations from ballistic transport in serially connected 1D regions occur at much longer distances, where the contact to the 2DEG is already established. This is due to the larger subband separation in the QWR, which reduces subband scattering, leading to stronger deviation from n • G 0 values.…”

Adiabatic Edge Channel Transport in a Nanowire Quantum Point Contact Register

“…The impact of dimensional changeover on conductance quantization is critical. De Picciotto et al , and Dwir et al have investigated a series connection of one-dimensional (1D) quantum wires formed by means of epitaxial overgrowth of the cleaved edge of a high-mobility 2DEG and in a V-groove sample, respectively. There, the 2D–1D scattering length between the two-dimensional contact area and the quantum wire was found to determine the emissivity into the 1D channel.…”

Contact block reduction method for ballistic transport and carrier densities of open nanostructures

“…Such a device can be realized by the cleaved edge overgrowth technique 32 and has been investigated experimentally extensively. [33][34][35][36][37] However, the complicated geometry has hampered realistic theoretical studies on transport properties so far. 38,39 To be concrete, we assume the barrier material to be p-doped and analyze the ballistic quantum transport characteristics of holes in the GaAs wells.…”