Ultracold Atoms and Molecules
My research is focused on experimental ultracold Atomic, Molecular and Optical (AMO) physics. Cooling atoms and molecules down to nano and micro Kelvin temperatures has paved the way towards coherent manipulation of them. As a result, ultracold atoms and molecules have transformed into a platform with high degree of controllability enabling the advancement of various studies across multiple disciplines, such as precision metrology, condensed matter physics, physical chemistry, and quantum information science. Below I summarize some of the research projects I have worked on within the field.
Synthetic quantum materials - Supersolid
Can we create a state of matter which shows properties of a superfluid flow and long-range spatial periodicity of a solid? Localized nature of the particles inside a solid do not seem to be compatible with the de-localized wave nature of a superfluid. Despite its paradoxical definition, the existence of supersolidity has been postulated for more than half a century. It triggered extensive experimental efforts focused on solid helium in torsion oscillators. However, observation of supersolidity in their system has been elusive due to other complex phenomena, such as quantum plasticity, masking the true effect.
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The concept of supersolidity was then generalized to include other superfluid systems which break the translational symmetry of space. It has been predicted that a Bose-Einstein condensate (BEC) with spin-orbit coupling can host a phase with the same symmetry breaking properties as the supersolids. Using standing waves of light to stabilize the supersolid phase was the key breakthrough we have achieved at MIT. Following the traditional methods used in solid-state physics, we utilized Bragg reflection of light to directly observe the existence of supersolidity.
Quantum simulation of spin-orbit coupling
Spin-orbit coupling is the mechanism for many intriguing new materials and phenomena, including topological insulators, the spin quantum Hall effect, Majorana fermions, and spintronics devices. Realizing spin-orbit coupling with ultracold atoms in a controllable way should make it feasible to illustrate fundamental aspects of topology in physics, and to explore possible applications in quantum computing.
While the new approach holds many promises, the conventional spin-orbit coupling scheme with ultracold atoms relied on driving Raman transitions between two internal hyperfine states of the atoms. For alkali atoms, such process requires near-resonant laser beams, which cause heating by spontaneous light scattering. We have developed a new method, where the Raman process couples two external orbital states to avoid the need for near-resonant laser light. For this, we engineered an asymmetric double-well potential by overlapping two standing waves of light. Pseudospins up and down are realized as the two lowest eigenstates of the double-well potential: localized to the left and right wells, respectively. Our work opens new avenues for probing topological phases of matter mediated by the spin-orbit coupling interaction.
Search for fundamental symmetry violation - electron electric dipole moment
By studying the shape of an electron, can we learn something profound about our Universe? The existence of a permanent electric dipole moment (EDM) of a fundamental particle breaks both parity (P-) and time (T-) reversal symmetry. This can be understood by imagining the coexistence of electric and magnetic dipole moments. As these moments change their directions in different ways under P- and T- reversals, the yet-to-be-discovered electric dipole moment is a powerful probe for symmetry violating effects.
Furthermore, the electron EDM creates a pathway towards testing theories beyond the Standard model. There have been continuous efforts to develop various extensions of the Standard Model – most notably the SuperSymmetry theory (SUSY) – to provide answers to one of the biggest mysteries facing us, the dominance of matter over anti-matter in the Universe. While high energy physicists are testing these theories at large scale particle accelerators, the measure of electron EDM is a cost-efficient way of producing complementary data to look for the symmetry violating effects that each of the theories predict, and can constrain their models. We have identified the X3Δ1 state of tungsten carbide molecule to be a good candidate for the electron EDM search due to its strong internal electric field and the molecular structure allowing for rejection of the systematic effects. Using a buffer gas cooling technique, I have created a low temperature beam of tungsten carbide molecules and performed high precision molecular spectroscopy. The measured molecular constants provided essential information for the electron EDM search.