Valley physics in Silicon

We are looking for a motivated candidate for a Phd project preceded by a master’s training on valley physics in silicon. The discovery of the ‘field effect’ was awarded the Nobel prize in Physics in 1956 [1] and has allowed the development of information technologies which have revolutionized our lives with computers and smart phones. The extraordinary interface between silicon and its oxide (SiO2) is at the heart of the field effect. At this interface, it is possible to switch on and off the electrical current flowing parallel to the interface with an electric field perpendicular to the interface. Researchers have recently shown that perpendicular electric field can also alter the valley occupation of silicon[2], a degree of freedom similar in many aspects to electron’s spin. From a fundamental point of view, this has led to the renewal of the study of the metal insulator transition in 2D [3] and the study of spin polarization [4]. From a more applicative perspective, this opens many opportunities to use this degree of freedom for information processing including quantum computing with the valley degree of freedom. Yet, little is known about the mechanisms leading to the lifting of valley degeneracy by electric field. The attendee will therefore be involved in electrical measurements of state of the art silicon MOSFETs under extreme conditions (low temperature and high magnetic fields) with the aim of elucidating the mechanisms and gaining better control of the valley degree of freedom and evaluating its effect on the electrical properties of silicon devices. After the period necessary to discover the subject, the attendee will be able to fully participate in defining his research objectives with more emphasis on device fabrication, electrical measurements or analysis of experimental data and modeling (or all these aspects) depending on his/her skills and preferences. Mentoring will be performed by X. Jehl, R. Maurand and V. Renard and will benefit from existing collaborations outside the group (LNCMI for very high magnetic fields measurements), CEA/Irig/Lsim for the theory.

References:

[1] The Nobel price in Physics 1956, Nobel organization web site.

[2] K. Takashina et al. Phys. Rev. Lett. 96 , 236801 (2006)

[3] K. Takashina et al. Phys. Rev. Lett. 106 , 196403 (2011)

[4] V. Renard et al. Nature Communications 6, 7230 (2015)

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