Browsing by Author "Kolodrubetz, Michael"
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Item Absence of Thermalization in Finite Isolated Interacting Floquet Systems(Amer Physical Soc, 2018-10-22) Seetharam, Karthik; Titum, Paraj; Kolodrubetz, Michael; Refael, Gil; Kolodrubetz, MichaelConventional wisdom suggests that the long-time behavior of isolated interacting periodically driven (Floquet) systems is a featureless maximal-entropy state characterized by an infinite temperature. Efforts to thwart this uninteresting fixed point include adding sufficient disorder to realize a Floquet many-body localized phase or working in a narrow region of drive frequencies to achieve glassy nonthermal behavior at long time. Here we show that in clean systems the Floquet eigenstates can exhibit nonthermal behavior due to finite system size. We consider a one-dimensional system of spinless fermions with nearest-neighbor interactions where the interaction term is driven. Interestingly, even with no static component of the interaction, the quasienergy spectrum contains gaps and a significant fraction of the Floquet eigenstates, at all quasienergies, have nonthermal average doublon densities. We show that this nonthermal behavior arises due to emergent integrability at large interaction strength and discuss how the integrability breaks down with power-law dependence on system size.Item Chronic IL-1 Exposure Drives Prostate Cancer Progression(May 2023) Dahl, Haley C 03/03/1993-; Delk, Nikki; Kolodrubetz, Michael; Palmer, Kelli; Kim, Tae Hoon; Winkler, Duane D.Prostate cancer (PCa) is the second most common cause of cancer-related deaths among American men. Androgen Receptor (AR) transcriptional activity is required for PCa tumor growth. Androgens regulate normal prostate tissue growth and differentiation via androgen receptor (AR) activation. Due to the role of androgens in prostate cancer, androgen-deprivation therapy (ADT), either through chemical or surgical castration or the use of anti-androgens, has become the standard therapy. However, ~10-20% of PCa patients will develop treatment resistance, referred to as castration-resistant PCa (CRPC). One mechanism of CRPC is the loss of dependence on AR for cell growth and survival. As such, over 84% of CRPC patients will develop incurable, lethal bone metastasis. Thus, it is important to uncover the mechanisms that drive CPRC. IL-1 is elevated in PCa patient tissue and serum and is associated with disease progression and metastasis. IL-1 is clinically relevant, but the role of IL-1 in CRPC development is not fully elucidated. Chronic inflammation is a known hallmark of cancer initiation and progression. Therefore, we exposed the cancer cells to IL-1 for several months to make the chronic IL-1 sublines, LNas1 and LNbs1. The chronic IL-1 sublines restore AR and AR activity but evolve AR independence and acquire a constitutive p62-KEAP1 interaction. p62 is a multi-domain, multifunctional pro-survival protein that mediates autophagic turnover of damaged proteins and organelles, promotes NF-κB inflammatory signaling and induces NRF2 antioxidant signaling through its binding to and sequestering of KEAP1 from NRF2. Despite constitutive p62- KEAP1 binding, the chronic IL-1 sublines only show elevated NRF2 signaling in the NRF2 target genes, HMOX1 and GCLC. Furthermore, the chronic IL-1 sublines evolve insensitivity to IL-1 extracellular signaling and, thus, do not activate NF-κB nor NRF2 signaling. Thus, the regulation and function of the constitutive p62-KEAP1 interaction in the chronic IL-1 sublines is novel. To investigate the regulation and function of the constitutive p62-KEAP1 interaction in PCa cells chronically exposed to IL-1, I dissected p62-KEAP1 regulation and function under the oxidative stress-inducing stimulus, androgen deprivation. Under androgen deplete conditions, there is attenuation of HMOX1 and overexpression of GCLC in the chronic IL-1 sublines. This suggests that there is active but aberrant NRF2 signaling that may allow these cells to be primed to withstand oxidative stress. Furthermore, knockdown of KEAP1 results in upregulation of HMOX1 suggesting that KEAP1 negatively regulates HMOX1. Both HMOX1 and GCLC function as an antioxidant to attenuate iron-induced lipid ROS and thus regulate iron- dependent cell death known as ferroptosis. Based on what we have found, we hypothesize that the sublines activate a novel pathway that primes them to withstand ferroptosis-induced cell death.Item Floquet Quantum Criticality(National Academy of Sciences) Berdanier, W.; Kolodrubetz, Michael; Parameswaran, S. A.; Vasseur, R.; 0000-0001-5628-3300 (Kolodrubetz, M); Kolodrubetz, MichaelWe study transitions between distinct phases of one-dimensional periodically driven (Floquet) systems. We argue that these are generically controlled by infinite-randomness fixed points of a strong-disorder renormalization group procedure. Working in the fermionic representation of the prototypical Floquet Ising chain, we leverage infinite randomness physics to provide a simple description of Floquet (multi)criticality in terms of a distinct type of domain wall associated with time translational symmetry-breaking and the formation of “Floquet time crystals.” We validate our analysis via numerical simulations of free-fermion models sufficient to capture the critical physics.Item Inversion Asymmetry, Flavortronics, and Nonlinear Optics in Two-dimensional Materials(August 2022) Cheung, Patrick; Zhang, Fan; Stern, Robert; Gartstein, Yuri; King, Lindsay J.; Kolodrubetz, Michael; Zhang, ChuanweiInterests in two-dimensional (2D) materials have grown tremendously after the successful isolation of a single layer graphene. The properties of 2D materials are often very different from their 3D counterparts. They offer great flexibilities in tuning their electronic and optical properties through numerous ways. For example, electronic properties not only greatly vary with the number of layers in the materials, they can also depend strongly on the relative twists among different layers. Besides scientific advances and discoveries, these findings have led to enormous efforts being put in band gap engineering and the more recent moir ́e engineering to ensure that they fulfill their unprecedented potential in technological applications. In this dissertation, we study this emerging and exciting platform. Our era of electronics is made possible through advances in semiconductor technology based on the precise manipulation of electronic charge degree of freedom. However, there are additional degrees of freedom, such as spin, layer and valley, that electrons in materials may possess. Methods to fabricate workable devices based on the manipulation of these degrees of freedom to process and store information have been extensively studied in the literature. Here, we take a step further. We consider another degree of freedom, SU(3) flavor, that exists in the so-called Q-valleys of n-type few-layer transition metal dichalcogenides. In the quantum Hall regime, Landau levels form triplets that are each three-fold degenerate. When each Landau level triplet is one-third filled or empty, we predict that a pure flavor nematic phase and a flavorless charge-density-wave phase will occur respectively below and above a critical magnetic field. Electrons carry flavor-dependent electric dipole moments even at zero magnetic field, giving rise to a nematic ferroelectric state. We further show that the flavor degree of freedom can be manipulated by an electric field, leading to a new concept: flavortronics. The local density of states of electrons in materials will be modified when they are scattered off impurities. This results in quasiparticle interference (QPI) that can be probed by scanning tunneling spectroscopy. We then study QPI of Q-valley electrons scattering off localized non- magnetic and magnetic impurities. More importantly, we propose that QPI provides a way to observe the above predicted nematic ferroelectric state. Finally, we study a moir ́e metamaterial, namely twisted double bilayer graphene (TDBG). The electronic and optical properties in twisted multilayer systems are very different from the single layer counterpart. The highly tunable quantum geometric properties of TDBG give rise to tunable photoresponses that are closely related to the polarization states, power and wavelength of the incident light. This close relationship enables us to generate a set of photovoltage maps that can be used to train a convolutional neural network to decode the properties of an unknown incoming light from its unique photovoltage map. This enables an unprecedented intelligent light sensing in an extremely compact, on-chip manner.Item Light-emitting Electrochemical Cells: Temperature Dependence and Host-guest-systems(2022-05-01T05:00:00.000Z) Bowler, Melanie; Slinker, Jason D; Chiou, Sy Han Steven; Lv, Bing; Goeckner, Matthew J; Smaldone, Ronald A; Kolodrubetz, MichaelLight-emitting electrochemical cells (LECs) yield high efficiency and long-lasting performance in a simple device architecture. Due to the ionic nature of these devices, electric double layer formation occurs at the electrodes in response to an applied field, producing efficient charge injection and recombination for light emission. LECs from perovskites, nanoparticles, or organic small molecules have potential as thin, conformable, lost-cost solutions for seamless integration in light-emitting applications. Understanding the interplay of electronic and ionic processes of LECs is necessary to improve the luminance, efficiency, stability, and lifetimes for this potential to be actualized. This dissertation focuses on temperature-dependent studies of ionic, electronic, and optical properties of LECs and host-guest systems to improve stability, increase efficiency, and control color. We established that iridium LECs show superior temperature stability to their ubiquitous ruthenium counterparts, resisting radiant flux loss until 67 °C (152 °F). To understand the mechanistic origin of this superior stability, the temperature-dependence of the photoluminescence of iridium and ruthenium complexes was measured. Although textbooks have asserted that iridium complex stability superiority is due to energetic suppression of non-luminescent and antibonding states, it was alternatively found that this superiority was due to favorable radiative recombination rates relative to nonradiative transitions. We implemented novel small-molecule ionic hosts based on carbazole derivatives with ionic transitional metal complex (iTMC) guestsfor use in LECs. These hosts demonstrated wide, tunable bandgaps and accessible oxidation and reduction features, consistent with our design parameters. LECs with a PBI-CzH host demonstrated superior performance, where PBI is 4- bromophenylbenzimidazole, and CzH is an unsubstituted carbazole unit. These LECs achieved 624 cd/m2 luminance at 3.80% external quantum efficiency, competitive in the field of iTMCs. Xray diffraction suggested that host packing caused the superior performance of the PBI-CzH host and offered a key design insight for future LEC hosts. A novel ionic iridium complex guest was prepared to be used in conjunction with a CsPbBr3 perovskite host and a polyelectrolyte to achieve high performance in a perovskite light-emitting device with a single-layer structure. Maximum luminance (10600 cd/m2 ), current efficiency (11.6 cd/A), and power efficiency (9.04 Lm/W) were achieved at a 14% weight fraction of the guest, and voltage-tunable color was demonstrated. These results show improvement for all reported metrics for perovskite host devices, demonstrating the potential for a host-guest approach with radiationally designed ionic emitters in perovskite LECs. Finally, we followed the low-temperature performance of current, electroluminescence, and photoluminescence of perovskite LECs to reveal the effects on ionic transport, electronic transport, and optical properties. Initially, lowering the temperature increased device efficiency. However, the efficiency was found to decrease as the temperature decreased from 240 K and below. Differential scanning calorimetry was used to assess morphological changes induced by the polyelectrolyte. Ultimately, it was revealed that the interplay of these factors greatly depends on the mechanical properties of the polyethylene oxide electrolyte, and the suppression of the glass transition could substantially improve low-temperature device performance.Item Low-Temperature and Photoactivated CVD on Organic Substrates(2021-12-01T06:00:00.000Z) Salazar, Bryan G.; Walker, Amy V.; Kolodrubetz, Michael; Balkus Jr., Kenneth J.; Gelb, Lev D.; Smaldone, Ronald A.Chemical vapor deposition (CVD) is an attractive technique for depositing metallic thin films on organic substrates. However, CVD often uses temperatures > 500 °C to initiate precursor decomposition and generate highly reactive species. This can be problematic when using attempting to deposit on organic thin films as they can degrade at temperatures < 200 °C. Here we offer an alternative to thermal activation by using photolysis to generate reactive species at room temperature. In this work we monitor decomposition pathways of photoactivated precursors by employing TOF SIMS to identify molecular species remaining on the surface as well as test the integrity of the surface post-deposition. XPS is used to identify organic surface- metal interactions, and finally RGA is used to identify gas-phased decomposition products to further identify photolytic pathways. In identifying the decomposition pathway, we aim to use this understanding to further improve the deposition of metal on organic substrates.Item Modeling Fill Factor Losses in Organic Solar Cells(2022-08-01T05:00:00.000Z) Kramer, Aaron A; Vandenberghe, William G; Kolodrubetz, Michael; Dieckmann, Gregg R; Hsu, Julia W P; Zhang, Fan; Izen, Joseph M.Determining how certain electronic devices can outperform other devices is of immense interest in the modern world. Many advance experimental characterization techniques have been applied such as X-ray diffraction, scanning electron microscopy, and transmission electron microscopy to aid in the understanding of device performance. However, simulations often offer a more effective complementary to experiments in discovering the physics governing new materials. First principles or ab initio simulations offer a big advantage since they require no experimental information at all. Empirical methods, on the other hand, need previously determined experimental values to match the experiment. In this thesis, I explain how I further simplify the present understanding of emerging materials from a theoretical perspective. I first discussed why experiments observed fill factor losses in dilute-donor organic solar cells by performing kinetic Monte Carlo simulations. From my kinetic Monte Carlo simulations, I discovered a linear relation between the fill factor and the fraction of donors touching the anode and concluded that fill factor losses are due to donors not touching the anode. In addition to studying the fill factor losses, I studied solvent effects on the highest occupied molecular orbital energy of solute molecules by implementing a first solvation shell method. A first solvation shell is a mix between implicit solvent methods and explicit solvent methods. I found that present implicit solvent methods are not sensitive to solvent choice because those methods cannot discern how solvents and ambient temperature perturb the solute geometries. Finally, I also studied how the bandgap of Tellurium becomes more suitable as a channel material when scaled to extremely small sizes (~1-3 nm).Item Paths to Non-ergodic Quantum Dynamics: From Cavity QED to Strong Zero Modes(December 2022) Rahmanian Koshkaki, Saeed; Pereira, Luis Felipe; Kolodrubetz, Michael; Lv, Bing; Vandenberghe, William; Zhang, Fan; Zhang, ChuanweiRecent advances in cold atoms experiments and the development of superconducting circuits have revolutionized the way we can examine, observe and implement new physical phenomena. In such systems, we can realize new classes of quantum systems which exhibit non-equilibrium quantum phenomena. These systems have attracted mcuh attention in the past two decades as they possess new physics absent in equilibrium. Beside interesting rich physics to learn more about quantum systems, understanding non-equilibrium systems are crucial in developing future technologies such as quantum computation and communication. Given that many open questions needed to be answered in the study of non-equilibrium quantum systems, in this dissertation we will present our theoretical and numerical attempts in providing answers to some of these questions. One of the key features of the non-equilibrium system is how the dynamical properties of quantum systems cane be characterized in different conditions. Here we will present our result on two different mechanism a system can avoid ergodicity. Many-body localization (MBL) is an extension of Anderson localization to interacting systems, where adding strong enough disorder (breaking translational symmetry by adding random potential such as impurity in crystals) can impede the conductivity (system becomes insulator) in the quantum system. Most of the known MBL systems are short- range interacting particles, but in this dissertation, we will discuss MBL in the presence of coupling of the matter to cavity/circuit QED mode where the combined system becomes long-range interacting. We will study the two cases of weak coupling and strong coupling regimes and will derive the effective Hamiltonian using the high-frequency expansion for each case of coupling strength. We predict that the cavity QED has new localization behaviors such as an inversion of the mobility edge where the high-energy states are localized and low-energy states are delocalized. Also in the strong coupling limit, we observed that using the idea from coherent destruction of coupling the system can show signs of localization for photon number as low as n ∼ 2. The rest of this dissertation is devoted to understanding how a clean system (no disorder) can possess symmetry-breaking edge modes indefinitely, or for a long enough but finite time. The case with infinite lifetime edge mode is called strong mode (SM) and the case with finite lifetime edge mode is known as almost strong mode (ASM). Our system of interest is a clock Z3 model which is an extension of the Ising Z2 models. In the clock model (Baxter and modified Baxter) we found that the chirality of the interaction is essential in deriving the exact edge mode in the Hermitian model but removing the hermiticity (controlled by a parameter β), the effect of chirality on the stability of the edge mode becomes less important. We attempt to use different numerical and approximation techniques such as Krylov Hamiltonian and dynamical signature to characterize the edge mode in a Z3 model.Item Robustness of Quantum Control in Noisy Environments(2021-07-23) Timms, Christopher Ian; Kolodrubetz, MichaelDriving can be used as an effective tool in engineering quantum states of matter and producing states that can not otherwise be seen. In this PhD dissertation, I first discuss our research exploring the stability of periodically-driven topological phases to noise. We find that certain topological signatures remain robust to noise that breaks Floquet symmetry. We extend these studies to the use of noise that is determined by a quasi-periodic function, as opposed to white noise, and find similar results. I then discuss the second topic of my PhD dissertation in which drive is used to improve quantum sensing. Specifically, we model the use of protocols, which define how a series of π or non-π pulses are implemented, that serve to modify the quantum state of an ensemble of particles, such that they can be optimized for quantum sensing. Using π pulse protocols for quantum sensing already has a wide variety of potential applications in areas like materials science and bio-sensing. As shown by this dissertation, extending these studies to include the use of non-π pulses serves to dramatically enhance the optimization of the sensitivity. Furthermore, we explore the hardness of the problem of finding the optimal protocol by finding an analogue of the descent of the protocol down the optimal control landscape using stochastic gradient descent to that of a spin-glass evolving towards its ground state after experiencing a quench.Item Silicon-based Thermoelectrics for Microelectronic Applications(2022-05-01T05:00:00.000Z) Dhawan, Ruchika; Lee, Mark; Dabkowski, Mieczyslaw; King, Lindsay J.; Slinker, Jason D.; Lv, Bing; Kolodrubetz, MichaelThe large advancement of miniature (∼0.1 cm2 area) silicon integrated circuit (IC) sensors and networking devices for internet-of-things (IoT) and biomedical electronics has prompted the problem of making such devices energy-autonomous, i.e., how to energize such devices reliably and sustainably when they are embedded in isolated environments that have no sunlight for photovoltaics, have no access to wall plug power, and cannot routinely be accessed for regular maintenance or battery replacement. Recently, significant interest has developed in small microelectronic thermoelectric generators (µTEGs) as an autonomous energy source for IoT and biomedical devices wherever a reliable thermal gradient exists. Miniaturized solid-state thermoelectric (TE) devices can interconvert thermal gradients and electric fields for power generation or refrigeration. Most current research on TE technology concentrates on developing new materials with high TE figure-of-merit ZT = α 2σ κ T, where α, κ, σ and T are the material’s Seebeck coefficient, thermal conductivity, electrical conductivity, and the mean operating temperature, because the ideal thermodynamic maximum efficiency of a TEG increases with the ZT of the materials used to form the thermopile. However, high ZT materials are usually toxic or non-earth abundant, expensive to manufacture, and are generally incompatible with the Si IC fabrication process, all of which can substantially increase the cost of integration with standard IC devices, making these materials inappropriate for large-scale integration. Bulk Si is neglected for TE applications because of its poor ZT ∼ 10−2 − 10−3 near room temperature due to its large thermal conductivity. Recently, new opportunities for TE materials have been created because of significant advances in the scientific understanding of nanostructure effects on TE properties. It is now thought to be possible to build nanostructured silicon TEGs with a large reduction in κ due to significant phonon scattering, thus enhancing the ZT of material. In this research, µTEGs with a small area (<< 1 mm2), using doped Si and Si0.97Ge0.03 as the TE material, are fabricated on a standard industrial Si IC process line following the same protocols and process flows used to make commercial IC devices. These µTEGs can generate very large specific power densities (power per unit area for heat flow per square of temperature difference, ∆T ) of 84 µWcm−2K−2, which is comparable to the best existing high ZT bulk TEGs. Moreover, these miniature Si µTEGs can generate voltages exceeding 1.5 V with several µA of current using commonly encountered ∆Ts ∼ 20 to 25 K, which are sufficient to properly energize some existing commercially available low-power IoT ICs. These µTEGs are compatible with industrial fabrication techniques so can be directly integrated on-chip in the same process flow with the circuits they support, providing one solution to energy autonomy at an extremely low marginal cost. These Si-based µTEGs build on an unconventional approach to µTEG device design that emphasizes the application of device physics and circuit engineering principles to optimize a µTEG’s generated power per unit area at any given ∆T, rather than focusing on the thermodynamic efficiency, for applications with a high specific power density as the primary requirement. Using the ability of CMOS processing to fabricate ultrahigh density devices with low packing fraction, we can integrate ∼ 104 thermocouples cm−2 while maintaining a reasonable temperature gradient across the device, thereby producing high total power and voltage density despite relatively low efficiency per TE element. Modern Si processing is also very good at controlling parasitic thermal and electrical resistances, thus minimizing extrinsic degradation of overall TEG performance. Experimental results on µTEG fundamental performance characteristics (i.e. power and voltage generation) as well as TE Peltier cooling are presented. For optimizing the performance of TEGs, Physics-based models at both the material level including the effects of dopant concentration and small percentage Ge alloying, and the device design level including effects of parasitic electrical and thermal resistances and proper design of thermopile packing fraction have been developed. These models help optimize the TEGs to provide maximum power production in future designs. The wide acceptance of TE technology in a broad range of IC applications demands not only the research on suitable TE materials but also understanding the device physics along with the ability to determine basic TE properties such as Seebeck (α) and Peltier (π) coefficients at the device level. A wide range of literature exists on measurement of α but π is rarely measured and is usually derived from α using the first Kelvin relation, π = αT. We have developed a new method for measuring π in any TE device using only standard measured device parameters (i.e thermal impedance and short circuit current) without the need to correct for Ohmic heating (I 2R) that has historically made reliable measurements of π difficult. The experimental verification of the first Kelvin relation is illustrated using the independently measured value of α and π on commercial TE materials.