New avenues to computational technology: novel spin transport effects at the nanoscale – Ewelina Hankiewicz

Date: Mon. April 2nd, 2007, 12:30 pm-1:30 pm
Location: Rockefeller 221

The exponential increase of computational speed over time through miniaturization, known as Moore’s law, is now a thing of the past. This increase in speed is no longer due to our ability to make smaller devices, but in the control of heat dissipation. This is the so called problem 2020 when the temperature of a miniaturized computer, based on current power consumption trends, would be equal to the temperature of the sun. Clearly, this would be hazardous to the health of the consumer. Manipulation of electron spins through electric fields (so called spintronics) is one of the avenues sought for a new generation of devices. It combines standard nano/micro-electronics with spin-dependent effects and the advantage of lower power consumption. In this talk, I will discuss my recent research concerning two novel phenomena under this umbrella: the spin-Hall effect and the Aharonov-Casher effect. The spin-Hall effect is the generation of a steady spin current perpendicular to an externally imposed d.c. electric field. So far the spin-Hall effect has been measured by optical pump-probe experiments [1], and I will address the question how to distinguish between different processes contributing to this effect. Further, I will discuss our theoretical proposal to detect the spin-Hall effect in transport by using purely electrical means (the so called H-probe structure) [2]. The Aharonov-Casher effect is the quantum interference effect induced by an electric field. I will discuss my work performed in close collaborations with experimentalists concerning the observation of the Aharonov-Casher effect in HgTe/HgCdTe mesoscopic rings [3]. Our experiments and calculations have shown that the change of quantum mechanical phase of electron can be detected and manipulated directly.
[1] E. M. Hankiewicz, G. Vignale and M. Flatté, Phys. Rev. Lett. 97, 266601 (2006).
[2] E. M. Hankiewicz et al., Phys. Rev. B 70, 241301(R) (2004).
[3] M. König et al., Phys. Rev. Lett. 96, 076804 (2006).