Enhanced Zeeman splitting in Ga0.25In0.75As quantum point contacts

Abstract

The strength of the Zeeman splitting induced by an applied magnetic field is an important factor for the realization of spin-resolved transport in mesoscopic devices. We measure the Zeeman splitting for a quantum point contact etched into a Ga0.25In0.75As quantum well, with the field oriented parallel to the transport direction. We observe an enhancement of the Lande g-factor from |g*|=3.8 +/- 0.2 for the third subband to |g*|=5.8 +/- 0.6 for the first subband, six times larger than in GaAs. We report subband spacings in excess of 10 meV, which facilitates quantum transport at higher temperatures.Comment: [Version 2] Revtex4, 11 pages, 3 figures, accepted for publication in Applied Physics Letter

On‐Chip Andreev Devices: Hard Superconducting Gap and Quantum Transport in Ballistic Nb–In0.75Ga0.25As‐Quantum‐Well–Nb Josephson Junctions

“…This critical field is significantly smaller than the critical field of the Nb superconductor ≈3 T. If we assume that B c * is due to the Zeeman energy surpassing the induced superconductivity gap, i.e., gµ Β Β = Δ ind , our system with Δ ind ≈ 100 µeV will have a g-factor ≈3.4. This is consistent with the earlier report [20] and the recent experimental measurements of the g-factor in In 0.75 Ga 0.25 As based devices. [21] Our results together with the large g-factor and Rashba spin-orbit coupling in In 0.75 Ga 0.25 As quantum wells, which indeed can be varied by the indium composition, suggest that the Nb-2DEG-Nb system could be an excellent candidate to realize hybrid topological superconducting devices and to possible detection of Majorana modes.…”

“…[22] Design and fabrication of gated Nb-In 0.75 Ga 0.25 As-Nb junctions and formation of 1D systems may help to facilitate the detection of these modes in our devices. In S-Sm devices containing gated 1D channels, the g-factor in In 0.75 Ga 0.25 As can be increased from ≈3.6 for wide wires (nearly 2D) to >6 for narrow wires [20] so would allow lower B-field observation of Majorana modes. Further development of such devices, i.e., scaling the number of junctions up to 256, [23] provides the possibility for realizing real quantum devices applicable for quantum technology.…”

Field-orientation dependence of the Zeeman spin splitting in (In,Ga)As quantum point contacts

“…1 The strong spin-orbit interaction arises due to the narrow-band gap of InGaAs, which leads to a significantly higher Landé g factor compared to more conventional materials, such as GaAs, that are commonly used for realizing quantum devices. [2][3][4][5][6] Additionally, it has recently been shown in both experimental [7][8][9][10][11][12] and theoretical [13][14][15][16] studies that further enhancement in the g factor can be achieved by confining the carriers to a quasi-one-dimensional ͑quasi-1D͒ system such as a quantum wire or quantum point contact ͑QPC͒. This extra enhancement is due to the dominance of the exchange energy over the kinetic energy in low dimensions and at low electron densities.…”

“…[13][14][15] The g factor has been observed to be maximal when only a single subband is occupied and transport through the QPC is strictly 1D. 8,11 The quasi-1D g factor is not necessarily isotropic, depending both on the orientation of the field with respect to the QPC, and in some cases, the orientation with respect to crystallographic axes. Despite some studies of the anisotropy of the Zeeman splitting in quasi-1D hole systems in GaAs, 10,16,17 the directional dependence of the Zeeman splitting in quasi-1D electron systems in InGaAs has not been fully explored.…”

Interplay of fractional quantum Hall states and localization in quantum point contacts

“…Despite their simplicity, complex many-particle phenomena like g-factor enhancement [30][31][32] or the 0.7 anomaly [33][34][35][36][37][38] are observed. Furthermore, they offer the possibility of locally probing a physical system, which is for example used in charge detection experiments [39][40][41][42] or tunneling experiments in the quantum Hall regime [43][44][45] .…”