Bulletin of the American Physical Society
2024 APS March Meeting
Monday–Friday, March 4–8, 2024; Minneapolis & Virtual
Session N14: Quantum Quenches and Heat Transport 
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Sponsoring Units: DCMP Chair: Mihir Pendharkar, Stanford University Room: M100E 
Wednesday, March 6, 2024 11:30AM  11:42AM 
N14.00001: Exceptions to Fourier's Law at the Macroscale Kaikai Zheng, Shankar Ghosh, Steve Granick For the past two centuries, heat conduction within materials has been widely described as diffusion according to Fourier's law, with exceptions only observed at the nanoscale. However, this study aims to challenge the prevailing understanding of heat conduction by investigating its limitations at the macroscale. To achieve this, a homebuilt VacuThermoStretch IR System is utilized to conduct steady and pulse heating experiments. The results reveal anomalous temperature distributions and thermal energy propagation that cannot be explained by the classical Fourier's Law. These anomalies are observed across a range of materials, including slow amorphous polymer glass, crosslinked polymer rubber, and semicrystalline polymers, as well as fast metals. This suggests new strategies of heat transfer design. 
Wednesday, March 6, 2024 11:42AM  11:54AM 
N14.00002: Non Equilibrium Green's Function Approach for Modeling Carbon Nanotube Devices Pranav Vaidhyanathan, Natalia Ares, Kushagra Aggarwal, Mark T Mitchison, Juliette Monsel We introduce a comprehensive theoretical framework to explore a nonequilibrium nanoelectromechanical system (NEMS) based on a fully suspended carbon nanotube (CNT) device. This complex system presents several significant modeling challenges, most notably: (1) the lifetime broadening of the electronic energy level; (2) Coulomb interactions; (3) the mechanical motion of the CNT and its influence on electronic states; and (4) operation away from equilibrium. 
Wednesday, March 6, 2024 11:54AM  12:06PM 
N14.00003: Scaling of energy and power in a large quantum batterycharger model Lei Gao, Chen Cheng, WenBin He, Rubem Mondaini, XiWen Guan, HaiQing Lin We investigate a theoretical quantum batterycharger model, focusing on its potential emulation on concrete experimental platforms. Using a largespin representation, we first obtain the analytical form of the energy E_{B}(t) and power P_{B}(t), and their maximum values E^{max}_{B }and P^{max}_{B}, of the battery part by means of the antiferromagnetic HolsteinPrimakoff transformation within the lowenergy approximation. In this case, our results show that superextensive scaling behavior of P^{max}_{B }ensues. By further combining these with the ones obtained via exact diagonalization, we classify the dynamics of various physical quantities, including the entanglement between the battery and charger parts for system sizes encompassing over 10 000 qubits. Finally, by checking a diverse set of system configurations, including either a fixed battery size with a growing number of charger qubits or when both parts simultaneously grow, we classify the system size scalings of E^{max}_{B }and P^{max}_{B}, relating it with the entanglement entropy in the system. In agreement with the analytical results, robust superextensive behavior of P^{max}_{B} is also observed in this case. Our work provides an overall guide for expected features in experiments of quantum batteries emulated in multiqubit platforms, in particular ones that exhibit longrange couplings. 
Wednesday, March 6, 2024 12:06PM  12:18PM 
N14.00004: Harnessing synthetic axions to probe a cosmological axion Shuyang Cao, Daniel Boyanovsky Synthetic axions in topological insulators and Weyl semimetals couple to electromagnetism via a topological ChernSimons term, and so do cosmological axions which are compelling dark matter candidates. Therefore, synthetic and cosmological axions couple indirectly via intermediate states of two photons. We introduce a nonequilibrium effective field theory description of their hybridization or mixing in a medium. We find that a cosmological axion condensate may induce a synthetic axion condensate, and either condensate will induce a topological ChernSimons condensate in the intermediate photon states. Furthermore, the axion(s) twopoint correlation function features an emergent coherence, and displays quantum beats akin to a three level "V" system from a "whichpath" interference between the (quasi) normal modes. We analyzed the correlation functions of the intermediate twophoton state and highlighted distinct features that indicate the existence of ChernSimons condensate. These results may suggest the possibility of harnessing emergent axion quasiparticles in condensed matter systems to probe the cosmological axion as well as new tools to characterize properties of materials with axionic excitations. 
Wednesday, March 6, 2024 12:18PM  12:30PM 
N14.00005: Memory effects in the energy dissipation of anharmonic solids Cristobal I Vallejos, Jorge O Sofo Dissipation is commonly described by a systembath coupling. However, in systems with a macroscopic number of degrees of freedom, the bath can be the system itself, i.e., for excitations that only involve a subset of degrees of freedom, the dissipation and decoherence is produced by interactions with the remaining degrees of freedom. We use a simple model of coupled harmonic oscillators to explore the effects of local dissipation that can arise from large isolated systems, without the need to invoke a bath. When the oscillator potentials are purely harmonic, the energy of the system is transmitted by ballistic phonons that can propagate through the crystal lattice without scattering. Impurities and anharmonicities introduce memory effects in the time evolution of the phonons with the consequent loss of coherence. The energy transmission goes from ballistic to diffusive. We use a MoriZwanzig projection to encode anharmonic terms to all orders into the memory function. The result is an analytical expression for energy dissipation from a localized initial perturbation that describes the transition from ballistic to diffusive. A thermal conductivity coefficient can be extracted from the analysis. 
Wednesday, March 6, 2024 12:30PM  12:42PM 
N14.00006: Theoretical Investigation of nonMarkovian Dynamics of an Optomechanical System Acting as an Autonomous Quantum Heat Engine Miika Rasola, Vasilii Vadimov, Mikko Möttönen While new quantum technologies are being developed at an accelerating pace, the field of quantum thermodynamics [1] is attracting a lot of attention, as researchers are discovering a plethora of phenomena in quantum systems subjected to thermal fluctuations. The key example of such a quantum device is the quantum heat engine (QHE) [2]  a device operating at the quantum level, designed to interact with heat reservoirs and extract work from heat flow. We propose utilizing a wellknown quantum device, the optomechanical system, in a novel manner to realize an autonomous QHE. 
Wednesday, March 6, 2024 12:42PM  12:54PM 
N14.00007: Nonequilibrium Quantum Field Theory for Thermal Inhomogeneity in Thermoelectric Devices Yuan Gao, Khandker A Muttalib We generalized the standard nonequilibrium field theory framework to incorporate a temperature gradient across a thermoelectric device. The framework uses a temperaturedependent pseudoHamiltonian generated from the exact density matrix in the presence of nonuniform temperatures. We proposed a perturbation theory for otherwise free particles with small temperature gradients in long wires and obtained the Fermi and Boson distribution functions to first order accuracy. In addition, nonlinear thermal conductivity as a function of temperature difference is calculated. The framework should be adaptable to more general cases of temperature inhomogeneities in either fermionic or bosonic systems. 
Wednesday, March 6, 2024 12:54PM  1:06PM 
N14.00008: Inhomogeneous charge density wave states induced by quantum quenches Lingyu Yang, GiaWei Chern We study the postquench dynamics of the chargedensitywave (CDW) orders in the tV model. The ground state of the system is characterized by a checkerboard modulation of fermion numbers due to a perfect nesting of the Fermi surface at halffilling. An efficient realspace von Neumann equation method is employed to investigate the quench dynamics of an initially perfect CDW state. Our largescale simulations reproduce the three distinct postquench behaviors, the phaselocked coherent oscillation, Landaudamped, and overdamped oscillations. Moreover, we observe the emergence of intriguing inhomogeneous CDW states for quenches with particularly large increase of interaction strength. We perform quantitative characterizations of the quenchinduced inhomogeneity, and its relationship with the depth of quenched interactions. Our results demonstrate the spatial inhomogeneity in the quench dynamics of Isingtype order, which is perhaps one of the simplest examples of symmetry breaking, and underscore the importance of dynamical inhomogeneity in quantum quenches of manybody systems with more complex orders. 
Wednesday, March 6, 2024 1:06PM  1:18PM 
N14.00009: Quantum Interference Enhancement of the Spindependent Thermoelectric Response Justin P Bergfield, Joshua R Hendrickson, Runa X Bennett We investigate the influence of quantum interference and broken spinsymmetry on the thermoelectric response of nodepossessing junctions, finding a dramatic enhancement of the spinthermopower (S_{s}), figureofmerit (Z_{s}T), and maximum thermodynamic efficiency (η_{s}^{max}) caused by destructive quantum interference. Using manybody and singleparticle methods, we calculate the response of 1,3benzenedithiol and crossconjugated moleculebased junctions subject to an applied magnetic field, finding nearly universal behavior over a broad range of junction parameters withS_{s}, Z_{s}T, and η_{s}^{max} reaching peak values of 2π/√3 (k/e), 1.51, and 28% of Carnot efficiency, respectively. The influence of offresonant thermal channels (e.g. phonon heat transport) on the quantum interferenceenhanced spinresponse is also investigated. 
Wednesday, March 6, 2024 1:18PM  1:30PM 
N14.00010: Ultrafast transient absorption spectroscopy of strongly correlated Mott insulators Youngjae Kim We applied timeresolved transient absorption spectroscopy to systematically investigate the ultrafast optical responses of condensed matter systems. Under an intense pump pulse, absorption spectra indicate that the noninteracting electrons of band insulators produce a fieldinduced redshift, known as the dynamical FranzKeldysh effect, as commonly expected. In contrast to band insulators, in Mott insulators, unconventional spectra are observed which do not fully reflect the dynamical FranzKeldysh effect. While the spectra still exhibit fishbonelike structures mimicking the dynamical FranzKeldysh effect, they show a negative difference absorption below the band edge, rendering a blueshift. In addition, the decomposed calculation reveals that the negative difference absorption is mainly contributed from the creation and the annihilation of transient double occupancy, implying that the unconventional spectra are purely driven by the electron correlations. These demonstrated unconventional responses can guide us to better understanding of the correlationoriginated ultrafast electron dynamics in condensed matter systems. 
Wednesday, March 6, 2024 1:30PM  1:42PM 
N14.00011: Thermal transport in nanoelectronic devices in the zerotemperature limit Samuli Autti, Francis C Bettsworth, Kestutis Grigoras, David Gunnarsson, Richard P Haley, Alexander T Jones, Yuri A Pashkin, Jonathan R Prance, Mika Prunnila, Michael D Thompson, Dmitry E Zmeev Onchip demagnetization refrigeration has recently emerged as a powerful tool for reaching submK temperatures in nanoscale electronic devices, and other miniaturized cooling techniques are being actively investigated. In the zerotemperature limit, the thermal subsystems in a device are decoupled from one another, and the resulting slow dynamics have remained largely unexplained. We study a Coulomb blockade thermometer, made from arrays of tunnel junctions with integrated onchip copper refrigerant, both experimentally and numerically [1]. Comparing the two we show that dynamics in a multiinterface device cooled down to this temperature range are fully explained by a firstprinciples model. We can thus predict thermal dynamics in a generic device down to microkelvin temperatures. Our work outlines a lowinvestment recipe for bringing quantum technologies and fundamental nanoscience into this novel temperature range.
1. Autti et al., Phys. Rev. Lett. 131, 077001 (2023)

Wednesday, March 6, 2024 1:42PM  1:54PM 
N14.00012: Quantum refrigeration powered by dephasing in a superconducting circuit Simon Sundelin, Aamir Mohammed Ali, Claudia Castillo Moreno, Vyom Kulkarni, Simone Gasparinetti While dephasing noise frequently presents obstacles for quantum devices, it can become an asset in the context of quantum refrigerators. Quantum thermal machines have in recent years garnered more attention, but their implementation is hindered by the difficulties in measuring tiny heat flows. Here we demonstrate a novel quantum thermal machine that leverages dephasing noise to fuel a cooling engine in steady state. The device exploits symmetry selective couplings between a superconducting artificial molecule, comprised of two strongly flux tunable transmon qubits, and two microwave waveguides. These waveguides act as thermal reservoirs of different temperatures, which are regulated by employing synthesized thermal fields. The dephasing is controlled by injecting white noise through a third channel that is longitudinally coupled to the molecule. The interplay between individual thermalization to the baths and dephasing noise produces a heat current between the two baths, which we measure with a resolution below 1 aW using interleaved power spectral density measurements. By varying the temperature ratio of the thermal reservoirs, we demonstrated that the device can be operated as a quantum heat engine, thermal accelerator, and refrigerator. Our findings show the successful operation of a Brownian refrigerator and the simultaneous measurement of heat flows to multiple baths, opening new avenues for investigating quantum thermal machines in circuit quantum electrodynamics. 
Wednesday, March 6, 2024 1:54PM  2:06PM 
N14.00013: Nonequilibrium variable range hopping under DC bias in disordered electronic systems. Kunal Mozumdar, Jong E Han, Herbert F Fotso Variable range hopping is a mechanism of transport of electrons in a disordered electronic system which typically behave as insulators due to Anderson localization. In this study, we develop a theory of field assisted variable range hopping as a mechanism for insulatormetal transition in disordered systems. We develop a quantum mechanical model consisting of a 1D disordered insulating tight binding chain coupled to a dissipative fermionic bath and apply electric field across the chain. Our model shows the Mott 1/2law in equilibrium. Under electric field we compute the IV characteristics using nonequilibrium green's function method which shows us a nonlinear increase in the conductance with electric field. Our study indicates a disorder range in which the system shows variable range hopping and then goes into a transition from an typically insulator behavior to a metallic behavior. 
Wednesday, March 6, 2024 2:06PM  2:18PM 
N14.00014: Boundary Kondo Impurity with PTsymmetry and Beyond: a Bethe Ansatz approach Yicheng Tang, Natan Andrei, Pradip Kattel, Patrick Azaria, Parameshwar R Pasnoori The development of cold atom experimental techniques and superconducting quantum computers allows the experimental study of dissipative 1D quantum manybody systems. These dissipative systems are often modeled by nonHermitian Hamiltonians that typically arise when one wishes to provide an effective description of an open system coupled to an external environment. 
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