Controlling phonon squeezing and correlation via one- and two-phonon interference

Abstract

When ultrafast laser pulse strikes the crystal with a van Hove singularity in the phonon density of states, it can create a pair of anti-correlated in wave-vector phonons. As a result, the atomic fluctuations in either position or momentum become squeezed in such a way that their size might fall below the vacuum level. The ultrafast pulses can also generate a biphonon state in which the constituent phonons are correlated and/or entangled. Here we show that via the interplay between one-and two-phonon interference the bound and squeezed two-phonon state in (110) oriented ZnTe single crystal can be manipulated.

Photon number statistics uncover the fluctuations in non-equilibrium lattice dynamics

“…For this reason, in real materials, in addition to the thermal disorder, the atomic displacements are subject to fluctuations which are intrinsic to their quantum nature. While various evidences suggest that such quantum fluctuations may be of relevance in determining the onset of intriguing material properties, such as quantum para-electricity, charge density waves or even high temperature superconductivity 1 2 3 4 5 6 7 , the possibility of measuring quantum fluctuations in solids is the subject of an intense debate 8 9 10 11 12 13 14 15 16 17 18 19 20 21 .…”

Direct observation of two-phonon bound states in ZnTe

“…By virtue of the conservation principles that govern their creation, the two and phonons interfere destructively resulting in two-phonon coherence. We note in passing that the two phonon state generated by the second order Raman process can result in a squeezed lattice state [17,18].…”

Manipulation of Squeezed Two-Phonon Bound States using Femtosecond Laser Pulses

“…By the coherent control, we can steer the lattice into two opposite states: one corresponds to the situation (∆t = (n+1/2)Tc, n is the integer) when all atoms are almost at equilibrium position (the fluctuation of atomic displacements is small), while their momentum distribution is very broad; the other corresponds to the situation (∆t = nTc) when the atoms are at rest (the velocity distribution is narrow), but the displacement distribution is wide. In such way, we squeezed the uncertainties of either atomic displacement or momentum, depending on the phase delay between two TPBS excited by each pump [8]. In contrast to the amplitude modulation which behaves classically, the observed modulation of lifetime is difficult to explain within a classical interference scheme.…”