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VERSION:2.0
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SUMMARY:Bias driven non-equilibrium phase transitions
DTSTART:20240730T100000Z
DTEND:20240730T120000Z
DTSTAMP:20260612T105734Z
UID:9d2f4f65-f76e-4737-8929-f589ad312ede
SEQUENCE:2
CREATED:20240726T150431Z
DESCRIPTION:In this thesis\, we investigated bias-driven non-equilibrium q
 uantum phase transitions in a paradigmatic transport setup consisting of a
  quantum dot\, with an interacting charging energy\, connected to non-inte
 racting leads. We mapped out the non-equilibrium zero-temperature phase di
 agram as a function of interaction strength and bias voltage across the do
 t.Our central results are the behavior of charge susceptibility and curren
 t noise near the phase transition. Specifically\, we show that zero-freque
 ncy current fluctuations become critical and diverge as near the non-equil
 ibrium critical points. The charge susceptibility also diverges at the tra
 nsition.These results are achieved using a Random Phase Approximation (RPA
 ). Additionally\, we employ an Effective Stochastic Equation\, developed b
 y expanding the action to quadratic order in the fluctuations\, which yiel
 ds consistent results while offering a different physical interpretation.W
 e validated our findings in the high voltage limit\, where the system-lead
 s interaction becomes Markovian\, using the Lindblad master equation. At t
 his limit\, both the average current and current noise coincide with those
  of a non-interacting system\, consistent with the RPA effective field the
 ory.We used the Non-Crossing Approximation (NCA) to analyze the fermionic 
 energy distribution beyond RPA despite its limitations in modeling the hig
 h-voltage regime. NCA predicts qualitative changes in the electronic distr
 ibution near the critical point\, deviating substantially from Mean-Field 
 predictions.Our research demonstrates that current noise is a valuable too
 l for detecting and probing critical fluctuations at quantum critical poin
 ts. It also opens new pathways for studying other types of non-equilibrium
  voltage-driven transitions.
LAST-MODIFIED:20240726T150520Z
LOCATION:Online
URL:http://df.vps.tecnico.ulisboa.pt/pt/eventos/bias-driven-non-equilibriu
 m-phase-transitions/
X-ALT-DESC;FMTTYPE=text/html:<p data-block-key="hcea9">In this thesis\, we
  investigated bias-driven non-equilibrium quantum phase transitions in a p
 aradigmatic transport setup consisting of a quantum dot\, with an interact
 ing charging energy\, connected to non-interacting leads. We mapped out th
 e non-equilibrium zero-temperature phase diagram as a function of interact
 ion strength and bias voltage across the dot.<br/></p><p data-block-key="f
 o2f7">Our central results are the behavior of charge susceptibility and cu
 rrent noise near the phase transition. Specifically\, we show that zero-fr
 equency current fluctuations become critical and diverge as near the non-e
 quilibrium critical points. The charge susceptibility also diverges at the
  transition.<br/></p><p data-block-key="asal">These results are achieved u
 sing a Random Phase Approximation (RPA). Additionally\, we employ an Effec
 tive Stochastic Equation\, developed by expanding the action to quadratic 
 order in the fluctuations\, which yields consistent results while offering
  a different physical interpretation.<br/></p><p data-block-key="4a2bb">We
  validated our findings in the high voltage limit\, where the system-leads
  interaction becomes Markovian\, using the Lindblad master equation. At th
 is limit\, both the average current and current noise coincide with those 
 of a non-interacting system\, consistent with the RPA effective field theo
 ry.<br/></p><p data-block-key="b4fil">We used the Non-Crossing Approximati
 on (NCA) to analyze the fermionic energy distribution beyond RPA despite i
 ts limitations in modeling the high-voltage regime. NCA predicts qualitati
 ve changes in the electronic distribution near the critical point\, deviat
 ing substantially from Mean-Field predictions.<br/></p><p data-block-key="
 a8lfr">Our research demonstrates that current noise is a valuable tool for
  detecting and probing critical fluctuations at quantum critical points. I
 t also opens new pathways for studying other types of non-equilibrium volt
 age-driven transitions.</p>
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