COHERENT ELECTRICAL CONTROL OF A SINGLE HIGH-SPIN NUCLEUS IN SILICON
Nuclear magnetic resonance is a key analytical tool for physics, chemistry and medicine. It relies upon applying a combination of a static magnetic field to split the nuclear energy levels, and an oscillating magnetic field to induce transitions between them. Alternatively, for nuclei with quantum number I > 1/2 placed in crystals of low symmetry, the static energy splitting can be provided the nuclear quadrupole interaction, but transitions between the levels are always induced by oscillating magnetic fields.
Some recent experiments have shown electrical control of nuclear spins by modulating the electron-nuclear hyperfine tensor, thus using the electron as a transducer from the external electric field to the microscopic (magnetic) hyperfine field. Therefore, they represent a form of electrically-driven magnetic resonance.
Is it possible to induce nuclear transition using only pure electric fields?
I will present the experimental demonstration of coherent electrical control of a single 123Sb nuclear spin in silicon. The microscopic mechanism that underpins this demonstration is the coherent version of what was known since the 1960s as the Linear Quadrupole Stark Effect. It consists of a time-dependent modulation of the quadrupole coupling tensor, caused by the effect of the electric field on the bond orbitals around the atom. The bond orbital distortion, in turn, results in a local modulation of the electric field gradient at the nuclear site, which affects the quadrupole coupling and induces nuclear transitions. We observed coherent transitions for both 1 and 2 quanta of angular momentum, and demonstrated the ability to shift the nuclear resonance with static electric fields. A microscopic density functional theory provides quantitative agreement with the data, and insights into the delicate interplay between strain, electric fields and bond orbitals around the nucleus.