arXiv subjects

S. Y. Chou

Publications and source records attributed to S. Y. Chou.

6 recordsLinked to original sources

arXiv2001

Coherent electron transport in a Si quantum dot dimer

We show that the coherence of charge transfer through a weakly coupled double-dot dimer can be determined by analyzing the statistics of the conductance pattern, and does not require large phase coherence length in the host material. We present an experimental study of the charge transport through a small Si nanostructure, which contains two quantum dots. The transport through the dimer is shown to be coherent. At the same time, one of the dots is strongly coupled to the leads, and the overall transport is dominated by inelastic co-tunneling processes.

cond-mat.mes-hall↗

arXiv2001

Magnetically-induced reconstructions of the ground state in a few-electron Si quantum dot

We report unexpected fluctuations in the positions of Coulomb blockade peaks at high magnetic fields in a small Si quantum dot. The fluctuations have a distinctive saw-tooth pattern: as a function of magnetic field, linear shifts of peak positions are compensated by abrupt jumps in the opposite direction. The linear shifts have large slopes, suggesting formation of the ground state with a non-zero angular momentum. The value of the momentum is found to be well defined, despite the absence of the rotational symmetry in the dot.

cond-mat.mes-hall↗

arXiv2001

Spin-related transport in ultra small Si quantum dots

We investigated electron transport through ultra small Si quantum dots. We found that the $B$-dependence of energy levels is dominated by the Zeeman shift, allowing us to measure the spin difference between two successive ground states directly. In some dots the number of electrons N in the dot can be tuned starting from zero, and the total spin of the dot can be mapped as a function of N and B. For one of the dots we deduced that the dot becomes spontaneously polarized at N=6 with a large spin change ΔS=3/2, demonstrating the essential features of spin blockade. Surprisingly, for N>20, the transitions with ΔS>1/2 do not lead to the suppression of the corresponding peaks at low temperatures.

cond-mat.mes-hall↗

arXiv2000

Spin transitions in a small Si quantum dot

We have studied the magnetic field dependence of the ground state energies in a small Si quantum dot. At low fields the first five electrons are added in a spin-up -- spin-down sequence minimizing the total spin. This sequence does not hold for larger number of electrons in the dot. At high fields the dot undergoes transitions between states with different spins driven entirely by Zeeman energy. We identify some features that can be attributed to transitions between different spin configurations preserving the total spin of the dot. For a few peaks we observed large linear shifts that correspond to the change of the spin of the dot by 3/2. Such a change requires that an electron in the dot flips its spin during every tunneling event.

cond-mat.mes-hall↗

arXiv2000

Double-dot charge transport in Si single electron/hole transistors

We studied transport through ultra-small Si quantum dot transistors fabricated from silicon-on-insulator wafers. At high temperatures, 4K<T<100K, the devices show single-electron or single-hole transport through the lithographically defined dot. At T<4K, current through the devices is characterized by multidot transport. From the analysis of the transport in samples with double-dot characteristics, we conclude that extra dots are formed inside the thermally grown gate oxide which surrounds the lithographically defined dot.

cond-mat.mes-hall↗

arXiv1999

Non-Kondo zero bias anomaly in electronic transport through an ultra-small Si quantum dot

We have studied low-temperature single electron transport through ultra-small Si quantum dots. We find that at low temperatures Coulomb blockade is partially lifted at certain gate voltages. Furthermore, we observed an enhancement of differential conductance at zero bias. The magnetic field dependence of this zero bias anomaly is very different from the one reported in GaAs quantum dots, inconsistent with predictions for the Kondo effect.

cond-mat.mes-hall↗