We study interaction between two magnetic impurities on top of a two dimensional insulator in the presence of chiral phonons by second-order perturbation theory. We show that this exchange interaction arises from angular momentum of phonons through spin-chiral phonon interaction of the form of spin-orbit coupling. Analytical expressions of the interaction for acoustic and optical phonons are obtained. The exchange interactions are always positive due to the bosonic nature of phonons. We find that the exchange interactions for acoustic and optical phonons show power-law decay with respect to the distance between the two magnetic impurities and are proportional to the temperature of the system at high temperature.
We explore phonon-mediated quantum transport through electronic noise characterization of a commercial CMOS transistor. The device behaves as a single electron transistor thanks to a single impurity atom in the channel. A low noise cryogenic CMOS transimpedance amplifier is exploited to perform low-frequency noise characterization down to the single electron, single donor and single phonon regime simultaneously, not otherwise visible through standard stability diagrams. Single electron tunneling as well as phonon-mediated features emerges in rms-noise measurements. Phonons are emitted at high …
Phonon-mediated spin dynamics in a two-electron double quantum dot under a phonon temperature gradient
Institute of Industrial Science, The University of Tokyo（东京大学工业科学研究所）；Center for Emergent Materials Science (CEMS), RIKEN（理化学研究所新兴材料科学中心）；RIKEN Center for Quantum Computing (RQC), RIKEN（理化学研究所量子计算中心）；Pure and Applied Sciences, University of Tsukuba（筑波大学自然系统工学研究科）
In contradictin to the common concept that acoustic phonons can only travel inside a material medium, they can in fact "tunnel" across a vacuum gap with the help of piezoelectricity, transmitting a significantly stronger heat flux than that of blackbody radiation. Here, we present a theoretical formulation for the heat flux of such piezoelectrically mediated heat transfer, applicable to any anisotropic piezoelectric crystals with an arbitrary orientation. A few numerical results are demonstrated and compared to heat transfer driven by other close-range mechanisms, including near-field radiativ…
Phonon mediated drag in double layer two dimensional electron systems
报道了在双层二维电子气系统中研究声子介导阻力的实验结果。详细测量的温度，层间距，密度比，和匹配密度的阻力的依赖关系进行了讨论。并与理论结果作了比较[M. C. Bonsager等人，Phys.Rev.B57，7085（1998）]，其提出了新的耦合电子-声子集体模式的存在。层间距和密度的依赖性在匹配的密度与层间距低于2600 A的样品不支持这种模式的存在，表现出预期的独立的电子和声子系统的行为。然而，阻力的大小表明了另一种极限，即电子和声子强耦合的极限。对于更大的层间距，结果显示出与任一极限的预期行为的显著差异。
Metal-intercalated graphene on Ir(111) exhibits phonon signatures in inelastic elec- tron tunneling spectroscopy with strengths that depend on the intercalant. Extraor- dinarily strong graphene phonon signals are observed for Cs intercalation. Li interca- lation likewise induces clearly discriminable phonon signatures, albeit less pronounced than observed for Cs. The signal can be finely tuned by the alkali metal coverage and gradually disappears upon increasing the junction conductance from tunneling to con- tact ranges. In contrast to Cs and Li, for Ni-intercalated graphene the phonon signal…
In bilayer CrI3, experimental and theoretical studies suggest that the magnetic order is closely related to the layer staking configuration. In this work, we study the effect of dynamical lattice distortions, induced by non-linear phonon coupling, in the magnetic order of the bilayer system. We use density functional theory to determine the phonon properties and group theory to obtain the allowed phonon-phonon interactions. We find that the bilayer structure possesses low-frequency Raman modes that can be non-linearly activated upon the coherent photo-excitation of a suitable infrared phonon m…
In semiconductor materials, hot exciton cooling is the process by which highly excited carriers nonradiatively relax to form a band edge exciton. While cooling plays an important role in determining the thermal losses and quantum yield of a system, the timescales and mechanism of cooling are not well understood in confined semiconductor nanocrystals (NCs). A mismatch between electronic energy gaps and phonon frequencies in NCs has led to the hypothesis of a phonon bottleneck, in which cooling would be extremely slow, while enhanced electron-hole interactions in NCs have been used to explain co…
Localized excitons play a vital role in the optical response of monolayers of transition metal dichalcogenides and can be exploited as single photon sources for quantum information technology. While the optical properties of such localized excitons are vastly studied, the ultrafast capture process of delocalized excitons into localized potentials is largely unexplored. We perform quantum kinetic calculations of exciton capture via acoustic and optical phonons showing that efficient capture takes place on an ultrafast time scale. The polaron formation in the low-temperature limit leads to highe…
Organic semiconductor crystals stand out as an efficient, cheap and diverse platform for realising optoelectronic applications. The optical response of these crystals is governed by a rich tapestry of exciton physics. So far, little is known on the phonon-driven singlet exciton dynamics in this class of materials. In this joint theory-experiment work, we combine the fabrication of a high-quality oligoacene semiconductor crystal and characterization via photoluminescence measurements with a sophisticated approach to the microscopic modeling in these crystals. This allows us to investigate singl…
Unlike the chirality of electrons, the intrinsic chirality of phonons has only surfaced in recent years. Here we report on the effects of the interaction between electrons and chiral phonons in two-dimensional materials by using a non-perturbative solution. We show that chiral phonons introduce inelastic \textit{Umklapp} processes resulting in copropagating edge states which coexist with a continuum. Transport simulations further reveal the robustness of the edge states. Our results hint on the possibility of having a metal embedded with hybrid electron-phonon states of matter.
We theoretically study the non-equilibrium correlations and entanglement between distant semiconductor qubits in a one-dimensional coupled-mechanical-resonator chain. Each qubit is defined by a double quantum dot (DQD) and embedded in a mechanical resonator. The two qubits can be coupled, correlated and entangled through phonon transfer along the resonator chain. We calculate the non-equilibrium correlations and steady-state entanglement at different phonon-phonon coupling rates, and find a maximal steady entanglement induced by a population inversion. The results suggest that highly tunable c…
When dressed particles (polarons) exchange quantum phonons, the resulting interactions are generally attractive. If the particles have hard-core statistics and the coupling to phonons is through the kinetic energy terms, phonon-mediated interactions are repulsive. Here, we show that such repulsive phonon-mediated interactions bind dressed particles into bipolarons with unique properties. These bipolaron states appear in the gap between phonon excitations, above the two-polaron continuum. While thermodynamically unstable, the bipolaron is protected by energy and momentum conservation and repres…
Pure dephasing is widely used in the literature to explain experimental observations on quantum dots in cavities. In many cases, its use is not enough and extra terms need to be "fictitiously" added to accomplish with the observed data as it is the case of cavity pumping of an unknown source. Here we controvert the validity of the pure dephasing mechanism as a source of decoherence and present a theoretical study based on the phonon-mediated coupling that can explain the emission spectrum and photon auto- and cross-correlation results in recent experiments without the need of any artificial as…
We propose and demonstrate a versatile technique to measure the lifetime of the one-phonon Fock state using two-color pump-probe Raman scattering and spectrally-resolved, time-correlated photon counting. Following pulsed laser excitation, the $n=1$ phonon Fock state is probabilistically prepared by projective measurement of a single Stokes photon. The detection of an anti-Stokes photon generated by a second, time-delayed laser pulse probes the phonon population with sub-picosecond time resolution. We observe strongly non-classical Stokes--anti-Stokes correlations, whose decay maps the single p…
We present a systematic theory of acoustic-phonon-mediated superconductivity, which incorporates Coulomb repulsion, explaining the recent experiment in Bernal bilayer graphene under a large displacement field. The acoustic-phonon mechanism predicts that $s$-wave spin-singlet and $f$-wave spin-triplet pairings are degenerate and dominant. Assuming a spin-polarized valley-unpolarized normal state, we obtain $f$-wave spin-triplet superconductivity with a $T_c\sim 20$ mK near $n_e=-0.6\times 10^{12}$ cm$^{-2}$ for hole doping, in approximate agreement with the experiment. We further predict the ex…
We investigate the electric response of chiral phonons on the low-buckled group-IVA monolayers by performing first-principles calculations. The vertical electric field breaks the degeneracy of phonon modes at high-symmetry $\pm K$ points of the phonon Brillouin zone, and the size of the phononic gap is proportional to the strength of the electric field. The gapped phonon modes at $\pm K$ possess chiralities with considerable phonon circular polarizations and discrete phonon pseudoangular momenta. The chiralities of phonons are robust against the variation of the field strength, but reversed by…
We develop a two-dimensional stochastic dissipative theory for the description of the transport of exciton polaritons accounting for their interaction with the environment of acoustic phonons. Our approach is based on the explicit modeling of the corresponding microscopic processes using a Monte Carlo framework rather than modeling from phenomenological principles. We show the dynamic formation of a condensate and investigate its characteristics, including threshold-like behavior in populations and the formation of spatial and temporal coherence at different temperatures of the environment and…
Understanding the origin of electron-phonon coupling in lead-halide perovskites (LHP) is key to interpreting and leveraging their optical and electronic properties. Here we perform femtosecond-resolved, optical-pump, electron-diffraction-probe measurements to quantify the lattice reorganization occurring as a result of photoexcitation in LHP nanocrystals. Photoexcitation is found to drive a reduction in lead-halide octahedra tilts and distortions in the lattice, a result of deformation potential coupling to low energy optical phonons. Our results indicate particularly strong coupling in FAPbBr…
We investigate the competition between acoustic-phonon-mediated superconductivity and the long-range Coulomb interaction in moiréless graphene multilayers, specifically, Bernal bilayer graphene, rhombohedral trilayer graphene, and ABCA-stacked tetralayer graphene. In these graphene multilayers, the acoustic phonons can realize, through electron-phonon coupling, both spin-singlet and spin-triplet pairings, and the intra-sublattice pairings ($s$-wave spin-singlet and $f$-wave spin-triplet) are the dominant channels. Our theory naturally explains the distinct recent experimental findings in Berna…
Phonon-mediated mid-infrared photoresponse of graphene
石墨烯在中红外频率下的光响应具有很高的技术兴趣，并且与可见光频率下的光响应相比，由根本不同的基础物理决定，因为所涉及的光子和基底声子的能量具有可比的能量。在这里，我们通过在宽频率范围（1000-1600 cm $^{-1}$）内测量空间分辨光电流来对石墨烯对中红外线的光响应进行光谱分辨研究。我们揭示了不同的机制，引起光电流产生的极性基板上的石墨烯。特别是，我们发现当光激发体或表面声子的SiO $_2$基板的光响应的增强。该工作为石墨烯基中红外热传感技术的发展奠定了基础。
Superconducting transition temperature of Pb nanofilms: Impact of the thickness-dependent oscillations of the phonon mediated electron-electron coupling
We investigate the chirality of phonon modes in twisted bilayer WSe2 and demonstrate distinct chiral behavior of the $K/K^\prime$ valley phonons for twist angles close to $0^{\circ}$ and close to $60^{\circ}$. In particular, multiple chiral non-degenerate $K/K^\prime$ valley phonons are found for twist angles near $60^{\circ}$ whereas no non-degenerate chiral modes are found for twist angles close to $0^\circ$. Moreover, we discover two sets of emergent chiral valley modes that originate from an inversion symmetry breaking at the moiré scale and find similar modes in moiré patterns of strain-e…
Topological phononic insulators are the counterpart of three-dimensional quantum spin Hall insulators in phononic systems and, as such, their topological surfaces are characterized by Dirac cone-shaped gapless edge states arising as a consequence of a bulk-boundary correspondence. We propose a theoretical framework for the possible superconducting phase in these materials, where the attractive interaction between electrons is mediated by topological phonons in nontrivial boundary modes. Within the BCS limit, we develop a self-consistent two-band gap equation, whose solutions show that the supe…
