arXiv subjects

Jinchao Mo

Publications and source records attributed to Jinchao Mo.

5 recordsLinked to original sources

arXiv2024

Sub-Doppler cooling, state preparation, and optical trapping of a triel atom

Ultracold gases of atoms from Main Group III (Group 13) of the Periodic Table, also known as "triel elements," have great potential for a new generation of quantum matter experiments. The first magneto-optical trap of a triel element (indium) was recently realized, but more progress is needed before a triel is ready for modern ultracold quantum science experiments in optical traps. Reaching this regime typically requires atoms that are cooled to the 10 uK level or below, prepared in pure quantum states, and confined in a laser field. Here we report the achievement of all three of these milestones in atomic indium. First, we perform polarization gradient cooling of an indium gas to 15 uK. Second, we spin polarize the gas into a single hyperfine sublevel of either the $5P_{1/2}$ indium ground state or the $5P_{3/2}$ metastable state. Third, we trap indium in a 1064 nm optical lattice, achieving a 3 s trap lifetime. With these results, indium is now a candidate for a next generation quantum research platform.

physics.atom-ph↗

arXiv2022

Emergent Topological Superconductor by Charge Density Wave Transition

Many-body instabilities and topological physics are two attractive topics in condensed matter physics. It is intriguing to explore the interplay between these phenomena in a single quantum material. Here, using the prototypical charge density wave (CDW) material monolayer 1H-NbSe$_2$ as an example, we show how momentum-dependent electron-phonon coupling drives the CDW transition from $3\times3$ to $2\times2$ phase under electron doping. More interestingly, we find the coexistence of superconductivity and nontrivial topology in one of the two $2\times2$ CDW phases, the latter of which is identified by the nonzero Z$_2$ invariant with ideal Dirac cone edge states near the Fermi level. A similar CDW transition-induced topological superconductor has also been confirmed in monolayer 1H-TaSe$_2$. Our findings not only reveal a unique and general method to introduce nontrivial topology by CDW transition, but also provide an ideal platform to modulate different quantum orders by electron doping, thus stimulating experimental interest.

cond-mat.supr-con↗

arXiv2022

Decisive role of electron-phonon coupling for phonon and electron instabilities in transition metal dichalcogenides

The origin of the charge density wave (CDW) in transition metal dichalcognides has been in hot debate and no conclusive agreement has been reached. Here, we propose an ab-initio framework for an accurate description of both Fermi surface nesting and electron-phonon coupling (EPC) and systematically investigate their roles in the formation of CDW. Using monolayer 1H-NbSe$_2$ and 1T-VTe$_2$ as representative examples, we show that it is the momentum-dependent EPC softens the phonon frequencies, which become imaginary (phonon instabilities) at CDW vectors (indicating CDW formation). Besides, the distribution of the CDW gap opening (electron instabilities) can be correctly predicted only if EPC is included in the mean-field model. These results emphasize the decisive role of EPC in the CDW formation. Our analytical process is general and can be applied to other CDW systems.

cond-mat.mtrl-sci↗

arXiv2022

Magneto-optical trap of a Group III atom

We realize the first magneto-optical trap of an atom in main group III of the Periodic Table. Our atom of choice (indium) does not have a transition out of its ground state suitable for laser cooling; therefore, laser cooling is performed on the $\lvert 5P_{3/2},F=6 \rangle \rightarrow \lvert 5D_{5/2},F=7 \rangle$ transition, where $\lvert 5P_{3/2},F=6 \rangle$ is a long-lived metastable state. Optimization of our trap parameters results in atoms numbers as large as $5\times10^8$ atoms with temperatures of order 1 mK. Additionally, through trap decay measurements, we infer a one-body trap lifetime of 12.3 s. This lifetime is consistent with background gas collisions and indicates that our repumpers have closed all leakage pathways. We also infer a two-body loss rate of $1.6\times 10^{-11}\ \mathrm{cm^3/s}$, which is comparable to those measured in alkali atoms. The techniques demonstrated in this work can be straightforwardly applied to other group III atoms, and our results pave the way for realizing quantum degenerate gases of these particles.

physics.atom-ph↗

arXiv2022

Zeeman slowing of a Group III atom

We realize the first Zeeman slower of an atom in the Main Group III of the periodic table, otherwise known as the "triel elements". Despite that our atom of choice (namely indium) does not have a ground state cycling transition suitable for laser cooling, slowing is achieved by driving the transition $\lvert 5P_{3/2},F=6 \rangle \rightarrow \lvert 5D_{5/2},F=7 \rangle$, where the lower-energy state is metastable. Using a slower based on permanent magnets in a transverse-field configuration, we observe a bright slowed atomic beam at our design goal velocity of 70 m/s. The techniques presented here can straightforwardly extend to other triel atoms such as thallium, aluminum, and gallium. Furthermore, this work opens the possibility of cooling Group III atoms to ultracold temperatures.

physics.atom-ph↗