by josh perry, editor
[email protected]

researchers at north carolina state university (raleigh, n.c.) have published a study that demonstrates the process for creating a liquid of electrons and electron holes at room temperature by perturbing monolayer transition metal dichalcogenides (tmdc).

monolayer mos₂. (nc state university)

according to an article on the nc state website, the researchers perturb semiconductors by exciting the material’s electrons with light. this creates a high density of electrons and holes, which are the spaces that electrons in higher states leave behind. if these excited electrons live long enough and the interaction is strong enough then an electron-hole liquid forms.

typically, this process happens around -150°c, which has limited the potential for this be applied to various technologies.

“tmdcs are semiconductors with properties that are of interest to anyone looking to make electronics operate more quickly and efficiently,” the article explained. “monolayer tmdcs are thin semiconductors, referred to as 2d because they are about one atomic layer thick. when materials are this thin, new physical properties emerge.”

the tmdc studied at nc state was molybdenum disulfide (mos₂). researchers mapped a phase diagram for the transition of the material from a gas to a liquid of electron holes. this diagram can be a blueprint for further studies.

the research was recently published in nano letters. the abstract stated:

“strong correlations between electrons and holes can drive the existence of an electron–hole liquid (ehl) state, typically at high carrier densities and low temperatures. the recent emergence of quasi-two-dimensional (2d) monolayer transition metal dichalcogenides (tmdcs) provides ideal systems to explore the ehl state since ineffective screening of the out-of-plane field lines in these quasi-2d systems allows for stronger charge carrier correlations in contrast to conventional 3d bulk semiconductors and enables the existence of the ehl at high temperatures.

“here we construct the phase diagram for the photoinduced first-order phase transition from a plasma of electron–hole pairs to a correlated ehl state in suspended monolayer mos₂.

“we show that the quasi-2d nature of monolayer tmdcs and the ineffective screening of the out-of-plane field lines allow for this phase transition to occur at and above room temperature, thereby opening avenues for studying many-body phenomena without the constraint of cryogenics.”