Ultrafast Switching to a Stable Hidden Quantum State in an Electronic Crystal

Abstract

Hidden states of matter may be created if a system out of equilibrium follows a trajectory to a state that is inaccessible or does not exist under normal equilibrium conditions. We found such a hidden (H) electronic state in a layered dichalcogenide crystal of 1T-TaS2 (the trigonal phase of tantalum disulfide) reached as a result of a quench caused by a single 35-femtosecond laser pulse. In comparison to other states of the system, the H state exhibits a large drop of electrical resistance, strongly modified single-particle and collective-mode spectra, and a marked change of optical reflectivity. The H state is stable until a laser pulse, electrical current, or thermal erase procedure is applied, causing it to revert to the thermodynamic ground state.

Towards properties on demand in quantum materials

“…4c 55 . In TaS 2 , 1.55-eV photoexcitation at low temperatures in the commensurate CDW phase results in a decrease in the resistance by three orders of magnitude arising from collective polaron reordering 54 . Similarly, at low temperatures, strained LCMO is a charge-ordered antiferromagnetic insulator where 1.55-eV excitation results in a collapse to a ferromagnetic metallic state, with strong magneto-elastic coupling being of importance 56 .…”

“…Impulsively induced electronic phases are typically short-lived, with lifetimes on the order of the electromagnetic pulse width or the energy relaxation time of the material. Yet, in quantum materials with corrugated free-energy landscapes, impulsive stimulation can trap the system in new phases at auxiliary free-energy minima, separated from the true ground states by a significant kinetic barrier [54][55][56] . These metastable phases persist indefinitely on experimental timescales but can be controllably erased by external parameters such as temperature and magnetic field.…”

Selective scattering between Floquet–Bloch and Volkov states in a topological insulator

“…Moreover, by controlling the light polarization we can negate Volkov states to generate pure Floquet-Bloch states. This work establishes a systematic path for the coherent manipulation of solids via light-matter interaction.The manipulation of solids using ultrafast optical pulses has opened up a new paradigm in condensed matter physics by allowing the study of emergent physical properties that are otherwise inaccessible in equilibrium 1,2,10 . An important example is provided by the Floquet-Bloch states 11 , which emerge in solids owing to a coherent interaction between Bloch states inside the solid and a periodic driving potential.…”

Optical freezing of charge motion in an organic conductor

“…1a) in Mott insulators [4][5][6][7][8][9][10] , chargeordered (CO) systems [11][12][13][14] and charge/spin density wave materials 6,[15][16][17][18][19][20] . Recently, the excitation of coherent phonons has been established as a leading strategy for the melting/ constructing of electronic orders 8,9,[15][16][17][18][19][20] . On the other hand, the development of strong electric fields (4MV cm À 1 ) of few-cycle optical pulses and recent theoretical studies using dynamical mean-field theory suggest that extreme non-equilibrium electronic states, such as Floquet states, negative temperatures and superconducting states 21,22 , can be achieved.…”