Effect of wire length on quantum coherence in InGaAs wires

Abstract

Quantum phase coherence lengths were experimentally measured in nanolithographic wires to investigate the effects of wire length on quantum decoherence, which can be limited by mechanisms such as coupling to an external classical environment. The work demonstrates that device geometry and coupling to the environment have to be taken into account in quantum coherence, of relevance in quantum technologies using electronic nanostructures. The low-temperature measurements of the quantum phase coherence lengths use quantum transport, specifically antilocalization, on wires fabricated from an InGaAs/InAlAs heterostructure. It is observed that longer wire lengths result in longer quantum phase coherence lengths, tending to an asymptotic value in long wires. The results are understood from the observation that longer wires average out the quantum decoherence introduced at the end sections by coupling to the external environment. The experimental results are quantitatively compatible with a model expressing reduced backscattered amplitude due to quantum interference at the wire ends.

Dynamic Nuclear Spin Polarization Induced by the Edelstein Effect at Bi(111) Surfaces

“…The inhibition of AL is visible in the data as an increase in τ SO with increasing B . Further, AL is a sensitive probe of quantum and spin coherence [27][28][29], and is sensitive to the time-reversal symmetry (TRS) breaking due to B [32,35,36]. The breaking of TRS due to the interplay of Zeeman splitting and SOI results in a quantifiable decrease in τ φ [35] with increasing B , also visible in the data.…”

“…B OH and the NP are in this work quantified by the weaklocalization quantum coherence corrections to the conductance of the Bi(111) surface states, caused by quantum interference between backscattered time-reversed carrier trajectories. At low temperatures T , the quantum coherence corrections lead to a resistance R with a specific dependence on an external magnetic field B ⊥ applied normally to the surface, in the absence of SOI known as weak-localization (WL) and under strong SOI known as (weak-)antilocalization (AL) [27][28][29][30]. The magnetoresistance (MR, R(B ⊥ )) due to AL is here determined by three characteristic times [27,28,30]: the elastic scattering time τ 0 as deduced from the areal surface state density N S and mobility µ, the SOI spin decoherence time τ SO , and the quantum phase decoherence time τ φ .…”

Precision measurement of electron-electron scattering in GaAs/AlGaAs using transverse magnetic focusing

“…The MC scattering time-scale τ MC , as a fundamental quantity in Fermi liquid theory, has been the subject of several calculations 15 – 18 . However, direct measurements of τ MC have been more elusive, only so far achieved at lower temperature T (≲4 K) by loss of quantum interference 19 – 21 , tunneling measurements 22 , or scattering measurements 23 , 24 . At higher T ≳ 4 K, the effect of MC scattering is to impose a local thermal equilibrium, and here experimental measurements of τ MC have only recently been enabled by the hydrodynamic transport regime 11 , 25 .…”