Tuning Coherent-Phonon Heat Transport in LaCoO₃/SrTiO₃ Superlattices

Abstract

Accessing the regime of coherent phonon propagation in nanostructures opens enormous possibilities to control the thermal conductivity in energy harvesting devices, phononic circuits, etc. In this paper we show that coherent phonons contribute substantially to the thermal conductivity of LaCoO 3 /SrTiO 3 oxide superlattices, up to room temperature. We show that their contribution can be tuned through small variations of the superlattice periodicity, without changing the total superlattice thickness. Using this strategy, we tuned the thermal conductivity by 20% at room temperature. We also discuss the role of interface mixing and epitaxial relaxation as an extrinsic, material dependent key parameter for understanding the thermal conductivity of oxide superlattices.

Interfacial Thermal Resistive Switching in (Pt,Cr)/SrTiO3 Devices

“…Strategies for controlling the heat flow in solids comprise the use of artificial interfaces, − domain walls in ferromagnets and ferroelectrics, − anisotropic mass distribution in nanowires, or point defects in crystalline solids, − among others . On the other hand, achieving a dynamic manipulation of heat transport implies the design of reconfigurable thermal states, − which poses a much bigger challenge, but it is essential for dealing with thermal energy management in electronics and other energy-demanding technologies .…”

GaAs/GaP Superlattice Nanowires for Tailoring Phononic Properties at the Nanoscale: Implications for Thermal Engineering

“…SLs with atomically clean interfaces have proven to be ideal systems for studying the crossover from particle to wave nature of phonons. , Indeed, several studies have demonstrated that this crossover can be obtained by controlling the SL periodicity, showing that a distinctive minimum in the lattice thermal conductivity can be achieved. ,, By taking advantage of wave interference phenomena of phonons, SLs can also serve as an ideal platform for creating phonon bandgap materials by selectively allowing (blocking) phonons with certain energies to propagate through them. Moreover, studies have shown that we can have control over coherent and incoherent phonon transport in SLs by means of band folding produced by the larger periodicity of the SL and the related changes in the phonon density of states and velocities. ,,, The understanding of particle-wave duality of fundamental excitations like electrons and photons has revolutionized modern electronics and optics.…”

“…SLs with atomically clean interfaces have proven to be ideal systems for studying the crossover from particle to wave nature of phonons. 10 , 25 Indeed, several studies have demonstrated that this crossover can be obtained by controlling the SL periodicity, showing that a distinctive minimum in the lattice thermal conductivity can be achieved. 11 , 26 , 27 By taking advantage of wave interference phenomena of phonons, SLs can also serve as an ideal platform for creating phonon bandgap materials by selectively allowing (blocking) phonons with certain energies to propagate through them.…”

Octahedra-Tilted Control of Displacement Disorder and Dielectric Relaxation in Mn-Doped SrTiO3 Single Crystals

“…Strontium titanate SrTiO 3 (STO) is a perovskite-type material that demonstrates incipient ferroelectric behavior and a quantum paraelectric low-temperature state. , It is believed that zero-point quantum fluctuations preclude the condensation of the polar soft mode and a macroscopic ferroelectric state does not form down to the millikelvin range. , At the same time, the dielectric permittivity reaches ∼10 4 without significant dispersion in the microwave frequency range, which is attractive for application in various types of tunable electronic devices, , nanotechnology, , and photocatalysis. , At ∼105–110 K, STO undergoes an antiferrodistortive transition to a nonferroelectric tetragonal phase formed by out-of-phase tilts of oxygen octahedra. , This improper ferroelastic Pm 3̅ m → I 4/ mcm phase transition has an intermediate nature between second-order and tricritical and is characterized by ultralow values of the order parameter (tilting angle of ∼2° at 1.5 K). , Despite this, the symmetry lowering through the phase transition leads to splitting of the polar soft mode (F 1u ) into two components (E u and A 2u ) and to the appearance of locally polar ferroelastic twin walls , remaining highly mobile down to low temperatures . Moreover, the competition between ferroelectric and antiferrodistortive instabilities (and accompanying strains) can have an even greater impact on the suppression of the polar state than quantum fluctuations. , …”

“…1,2 It is believed that zero-point quantum fluctuations preclude the condensation of the polar soft mode and a macroscopic ferroelectric state does not form down to the millikelvin range. 1,2 At the same time, the dielectric permittivity reaches ∼10 4 without significant dispersion in the microwave frequency range, 3 which is attractive for application in various types of tunable electronic devices, 4,5 nanotechnology, 6,7 and photocatalysis. 8,9 At ∼105−110 K, STO undergoes an antiferrodistortive transition to a nonferroelectric tetragonal phase formed by out-of-phase tilts of oxygen octahedra.…”