BGU Physics Department
Colloquium, Jan. 19th, 2012
Electrically tuned spin-orbit interactions in a semiconductor quantum dot
Yasuhiro Tokura, NTT Research Laboratories
Spin-orbit interaction (SOI) in semiconductors provides a unique knob for
electrical control of the spin qubits in quantum dots (QDs). In contrast to
the effect of SOI on the flying spins, where an effective magnetic field
appears in orthogonal to the electric field and
its momentum, SOI affects localized spins in a QD in a different manner.
Recently, we have systematically studied the SOI matrix elements of weakly
coupled InAs QD depending on the direction of external magnetic field.
Noticing a magic-angle of the in-plane magnetic field where the SOI matrix
element vanishes, we evaluate the symmetry of the relevant electronic
states. For a QD strongly coupled to the leads, the splitting of the Kondo
peak shows the amount of SOI. It is shown that the side gate voltage
controls the SOI matrix element, which enables an efficient coherent control
of spins by electric field. Finally, the electron spin g-tensor is also
shown to be controlled by the side gate, which suggests a possible
realization of g-tensor magneto resonance (g-TMR), which had only been
demonstrated for ensemble spins in a quantum well.
In collaboration with S. Takahashi, R. S. Deacon, A. Oiwa and S. Tarucha,
Dep. of Appl. Phys., Univ. of Tokyo.
 S. Takahashi, R. S. Deacon, K. Yoshida, A. Oiwa, K. Shibata, K. Hirakawa,
Y. Tokura and S. Tarucha,
Phys. Rev. Lett. 104, 246801 (2010).
 Y. Kanai, R. S. Deacon, S. Takahashi, A. Oiwa, K. Yoshida, K. Shibata,
K. Hirakawa, Y. Tokura, and
S. Tarucha, Nature Nanotechnology, 6, 511 (2011).
 R. S. Deacon, Y. Kanai, S. Takahashi, A. Oiwa, K. Yoshida, K. Shibata,
K. Hirakawa, Y. Tokura and
S. Tarucha, Phys. Rev. B 84, 041302(R) (2011).