Spin and phase coherence lengths in InAs wires with diffusive boundary scattering

J. Phys.: Condens. Matter

2016

Low-temperature quantum phase coherence lengths were experimentally measured in mesoscopic circular arenas fabricated on InGaAs quantum wells. The arenas are connected to wide sample regions by short side-wires, to investigate the effects of geometry in comparison to intrinsic materials properties on quantum decoherence. Universal conductance fluctuations were used to quantify the phase coherence lengths as a function of temperature and geometry. The experimental data show a dependence of phase coherence lengths on side-wire length and width-to-length ratio, which is accounted for by the competing effects of decoherence by coupling to the classical environment and Nyquist decoherence in ergodic wires. The observed decay of phase coherence lengths with the increasing temperature is consistent with expectations. The work demonstrates that geometrical effects influence the measured mesoscopic quantum decoherence.

Section: Introductionmentioning

confidence: 99%

Geometrical dependence of quantum decoherence in circular arenas with side-wires

Xie

Priol

J. Phys.: Condens. Matter

2016

“…Fourier spectra (below) will bear out this identification. The WAL [14,22,26,29,30] background extends to B ≈ 15 mT. In the array, WAL is observed to yield a stronger positive magnetoresistance signal than in unconfined macroscopic regions of the same 2DES.…”

Section: Results and Analysismentioning

confidence: 96%

Determination of time-reversal symmetry breaking lengths in an InGaAs interferometer array

Ren

J. Phys.: Condens. Matter

Vijeyaragunathan

et al. 2015

Quantum interference oscillations due to the Aharonov-Bohm phase were measured in a ring interferometer array fabricated on a two-dimensional electron system in an InGaAs/InAlAs heterostructure. Coexisting oscillations with magnetic flux periodicity h/e and h/2e were observed and their amplitudes compared as function of applied magnetic field. The h/2e oscillations originate in time-reversed trajectories with the ring interferometers operating in Sagnac-type mode, while the h/e oscillations result from Mach-Zehnder operation. The h/2e oscillations require time-reversal symmetry and hence can be used to quantify time-reversal symmetry breaking, more particularly the fundamental mesoscopic dephasing length associated with time-reversal symmetry breaking under applied magnetic field, an effective magnetic length. The oscillation amplitudes were investigated over magnetic fields spanning 2.2 T, using Fourier transforms over short segments of 40 mT. As the magnetic field increased, the h/2e oscillation amplitude decreased due to time-reversal symmetry breaking by the local magnetic flux in the interferometer arms. A dephasing model for quantum-coherent arrays was used to experimentally quantify effective magnetic lengths. The data was then compared with analytical expressions for diffusive, ballistic and confined systems.

“…The pairing of time-reversed trajectories (Cooperons) then leads to singlet and triplet contributions to the quantum correction δσ 2D . Under SOI L φ is thus replaced by a combination of length scales categorized as singlet and triplet lengths 19,21,[47][48][49][50][51][52] . The singlet length scale L 0,0 is expressed as:…”

Section: Materials and Sample Propertiesmentioning

confidence: 99%

“…The present work demonstrates the general importance of device geometry -particularly wire length-and of environmental coupling decoherence in studying and using quantum-coherence phenomena, among others in the characterization of new quantum states of matter realized in nanoscale systems. Previous studies relating to the dependence of quantum decoherence on device geometry and size have been performed in quantum wires [16][17][18][19][20][21][22][23][24] , quantum rings [25][26][27] , quantum ring arrays or cylinders 3,[28][29][30] , and quantum dots 9,12,[31][32][33] .…”

Section: Introductionmentioning

confidence: 99%

“…Each wire array consists of 20 parallel quasi-one-dimensional (Q1D) wires of given wire length L. Q1D denotes that the conducting wire width W is shorter than the mobility mean-freepath and than L φ , but substantially larger than the Fermi wavelength λ F such that lateral quantization and subband transport physics can be neglected. L φ as a measure of quantum coherence is in this work extracted as function of L and T by the quantum interference effect of weak antilocalization (WAL) 19,21,[34][35][36][37] . As a quantum interference effect, WAL is a sensitive probe of quantum coherence and originates in quantum coherence corrections to the conductance, caused by interference between backscattered time-reversed electron trajectories.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Effect of wire length on quantum coherence in InGaAs wires

Xie

2018

Phys. Rev. B

Self Cite

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.