Quantized Conductance in an InSb Nanowire

Abstract

Ballistic one-dimensional transport in semiconductor nanowires plays a central role in creating topological and helical states. The hallmark of such one-dimensional transport is conductance quantization. Here we show conductance quantization in InSb nanowires at nonzero magnetic fields. Conductance plateaus are studied as a function of source-drain bias and magnetic field, enabling extraction of the Landég factor and the subband spacing. KEYWORDS:Conductance quantization, ballistic transport, quantum point contact, subband, nanowire, InSb S emiconductor nanowires are the starting point of recently proposed topological systems. 1−3 A topological superconducting region arises in a one-dimensional (1D) semiconductor wire in the presence of a strong spin−orbit coupling when it is brought in contact with a superconducting material. On the boundary of the topological and nontopological wire regions Majorana fermions (MFs) are expected. 4 The MFs in a nanowire, quasi-particles that are an equal superposition of an electron and a hole, are candidate building blocks for faulttolerant quantum computation. 4,5 Moreover, 1D semiconductor wires with strong spin−orbit coupling have also been identified as a suitable platform for creation of a helical state. 6−8 In such a state spin and momentum of an electron are perfectly correlated, thereby creating spin polarization and allowing spin filtering, key themes in the field of spintronics. 9−11 InSb nanowires, alongside InAs and Si/Ge core−shell nanowires, are promising for study of topological and helical states, as they have a strong spin−orbit interaction, 12 and superconductivity can be induced in the nanowires. 13 Indeed signatures of MFs have been reported in hybrid semiconductor−superconductor InSb nanowire devices. 14 While in InSb nanowires the basic properties of spin−orbit interaction and induced superconductivity have each been separately investigated, the degree of fulfillment of the third requirement for creation of MFs, the 1D semiconductor wire, is not as well understood. In a 1D wire transport takes place in subbands, of which the occupation is controlled by an external gate voltage. While first schemes for detection of MFs required occupation of only a single subband near the superconducting contacts where the MFs form, 1,2 later proposals extended this condition to the multisubband regime. 15−17 Information about the energy spectrum of InSb nanowires needed to answer questions of subband occupation is however lacking. Moreover, MFs are affected by disorder in the wire, 17−19 of which the extent is unknown. Such disorder creates diffusive transport, instead of the ballistic transport implied in the 1D requirement. Subband occupation and disorder are also key issues in creation of helical states in InSb nanowires.The formation of subbands in (ballistic) 1D wires is shown in transport measurements by quantization of conductance, where each spin-degenerate subband contributes a conductance of g Q = 2e 2 /h. 20,21 In semiconductor nanowires conductan...

Surface-Guided Core–Shell ZnSe@ZnTe Nanowires as Radial p–n Heterojunctions with Photovoltaic Behavior

“…Past studies have shown that nanowires can grow along nanosteps and nanogrooves on nanofaceted sapphire substrate. 23,24,[40][41][42] This mode of guided growth, which we refer to as graphoepitaxy, has proven to be dominant over epitaxial growth, and essentially overrules the epitaxial relations between the sapphire and the nanowire. 28,29,40,41,44 This was the case also for the core-shell guided nanowires, as can be seen in figure 3.…”

Hybrid superconductor-quantum point contact devices using InSb nanowires

“…[4][5][6][7] However, preliminary experiments probing Majorana bound states in nanowires were marked by disorder and a soft superconducting gap in the tunneling regime. [4][5][6][7][8] Disorder in nanowire systems is known to break up ballistic transport 9,10 , which is a crucial ingredient for developing 1D topological superconductivity. 1,2,4,9 Additionally, disorder can produce zero-bias conductance signatures similar to Majorana bound states.…”

“…[4][5][6][7][8] Disorder in nanowire systems is known to break up ballistic transport 9,10 , which is a crucial ingredient for developing 1D topological superconductivity. 1,2,4,9 Additionally, disorder can produce zero-bias conductance signatures similar to Majorana bound states. 11 While the typical signature of ballistic 1D transport-quantized conductance-has been observed in InSb nanowires at high magnetic field 9 and more recently at zero-field, 19 clear demonstrations of ballistic transport at lower fields (< 1T, i.e., before the expected onset of topological superconductivity) in hybrid nanowire-superconductor systems are lacking.…”

“…1,2,4,9 Additionally, disorder can produce zero-bias conductance signatures similar to Majorana bound states. 11 While the typical signature of ballistic 1D transport-quantized conductance-has been observed in InSb nanowires at high magnetic field 9 and more recently at zero-field, 19 clear demonstrations of ballistic transport at lower fields (< 1T, i.e., before the expected onset of topological superconductivity) in hybrid nanowire-superconductor systems are lacking. Hence, in order to clearly demonstrate topological superconductivity and remove alternative mechanisms for observing zero bias conduction peaks, quantized conductance should be observed at zero magnetic field in NWs proximity coupled to superconductors.…”

Dynamic Transport in a Quantum Wire Driven by Spin–Orbit Interaction

“…The velocity of the excitations is strongly renormalized by SOI, which opens a way to fine-tune the charge and spin response of 1D electrons by changing the gate potential. One of the modes softens upon increasing the gate potential to enhance the current response as well as the power dissipated in the system.Introduction.-Today we are witnessing the burst of interest in the ballistic electron transport in quantum wires [1][2][3][4][5]. For the last three decades the quantum wires formed by electrostatic gating of a high-mobility two-dimensional (2D) electron gas have been the favorite playground to study quantum many-body effects in one-dimensional (1D) electron systems [6], where a strongly correlated state known as the Tomonaga-Luttinger liquid emerges as a result of the electron-electron (e-e) interaction [7].…”