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Ning Kang - Laboratoire de Physique des Solides d’Orsay

Non-equilibrium quantum criticality on the verge of charge order transition in the 1/4-filled organic conductors


Quantum phase transitions in a variety of strongly correlated systems have been intensively investigated recently. It has become possible to promote the formation of new quantum phases by tuning systems towards low-temperature quantum critical points. While quantum phase transitions in equilibrium systems have been the subject of extensive study, phase transitions caused by non-equilibrium drives have been studied much less extensively.

 

Phenomena of charge ordering in quarter-filled organic materials have been of renewed interest in the light of non-linear response in correlated electron systems. Here we show that the collapse of charge-ordered state in [EDT-TTF-CONMe2]2Br can be achieved not only by pressure, but also by an electrical field. A first-order phase transition in charge-ordered state can be turned toward zero with use of electric field and pressure as a control parameter, producing a quantum critical end point. In the close vicinity of melting line of charge-ordered state, this compound exhibits a strong non-linear current-voltage characteristic together with striking voltage oscillation. The phase diagram contains a transition that bifurcates to enclose a region with anomalous oscillation behavior. Our result suggest that this unconventional response of the system can be attributed to the formation of an inhomogeneous phase around the quantum critical point.

 

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