5 research outputs found
Two-dimensional superconductivity at heterostructure of Mott insulating titanium sesquioxide and polar semiconductor
Heterointerfaces with symmetry breaking and strong interfacial coupling could
give rise to the enormous exotic quantum phenomena. Here, we report on the
experimental observation of intriguing two-dimensional superconductivity with
superconducting transition temperature () of 3.8 K at heterostructure of
Mott insulator TiO and polar semiconductor GaN revealed by the
electrical transport and magnetization measurements. Furthermore, at the verge
of superconductivity we find a wide range of temperature independent resistance
associated with vanishing Hall resistance, demonstrating the emergence of
quantum metallic-like state with the Bose-metal scenario of the metallic phase.
By tuning the thickness of TiO films, the emergence of quantum
metallic-like state accompanies with the appearance of superconductivity as
decreasing in temperature, implying that the two-dimensional superconductivity
is evolved from the quantum metallic-like state driven by the cooperative
effects of the electron correlation and the interfacial coupling between
TiO and polar GaN. These findings provide a new platform for the study
of intriguing two-dimensional superconductivity with a delicate interplay of
the electron correlation and the interfacial coupling at the heterostructures,
and unveil the clues of the mechanism of unconventional superconductivity.Comment: 17 pages, 4 figure
Quantum metallic state in the titanium sesquioxide heterointerface superconductor
The emergence of the quantum metallic state marked by a saturating finite
electrical resistance in the zero-temperature limit in a variety of
two-dimensional superconductors injects a new momentum to the realm of
unconventional superconductivity. Despite much research efforts over last few
decades, there is not yet a general consensus on the nature of this unexpected
quantum metal. Here, we report the unique quantum metallic state within the
hallmark of Bose-metal characterized by the saturated resistance and
simultaneously vanished Hall resistance in the titanium sesquioxide
heterointerface superconductor TiO/GaN. Strikingly, the quantum bosonic
metallic state proximate to the two-dimensional superconductivity-metal
transition tuned by magnetic fields persists in the normal phase, suggesting
that the existence of composite bosons formed by electron Cooper pairs survives
even in the normal phase. Our work marks the observation of the preformed
electron Cooper pairs in heterointerface superconductor and sheds new light on
understanding the underlying pairing mechanism of unconventional
superconductivity.Comment: 6 pages, 4 figure
Spontaneous rotational symmetry breaking in KTaO interface superconductors
Strongly correlated electrons could display intriguing spontaneous broken
symmetries in the ground state. Understanding these symmetry breaking states is
fundamental to elucidate the various exotic quantum phases in condensed matter
physics. Here, we report an experimental observation of spontaneous rotational
symmetry breaking of the superconductivity at the interface of
YAlO/KTaO (111) with a superconducting transition temperature of 1.86
K. Both the magnetoresistance and upper critical field in an in-plane field
manifest striking twofold symmetric oscillations deep inside the
superconducting state, whereas the anisotropy vanishes in the normal state,
demonstrating that it is an intrinsic property of the superconducting phase. We
attribute this behavior to the mixed-parity superconducting state, which is an
admixture of -wave and -wave pairing components induced by strong
spin-orbit coupling. Our work demonstrates an unconventional nature of the
pairing interaction in the KTaO interface superconductor, and provides a
new platform to clarify a delicate interplay of electron correlation and
spin-orbit coupling.Comment: 7 pages, 4 figure
Direct observation of hot-electron-enhanced thermoelectric effects in silicon nanodevices
Abstract The study of thermoelectric behaviors in miniatured transistors is of fundamental importance for developing bottom-level thermal management. Recent experimental progress in nanothermetry has enabled studies of the microscopic temperature profiles of nanostructured metals, semiconductors, two-dimensional material, and molecular junctions. However, observations of thermoelectric (such as nonequilibrium Peltier and Thomson) effect in prevailing silicon (Si)—a critical step for on-chip refrigeration using Si itself—have not been addressed so far. Here, we carry out nanothermometric imaging of both electron temperature (T e) and lattice temperature (T L) of a Si nanoconstriction device and find obvious thermoelectric effect in the vicinity of the electron hotspots: When the electrical current passes through the nanoconstriction channel generating electron hotspots (with T e~1500 K being much higher than T L~320 K), prominent thermoelectric effect is directly visualized attributable to the extremely large electron temperature gradient (~1 K/nm). The quantitative measurement shows a distinctive third-power dependence of the observed thermoelectric on the electrical current, which is consistent with the theoretically predicted nonequilibrium thermoelectric effects. Our work suggests that the nonequilibrium hot carriers may be potentially utilized for enhancing the thermoelectric performance and therefore sheds new light on the nanoscale thermal management of post-Moore nanoelectronics
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Poly(ADP-ribosylation) of P-TEFb by PARP1 disrupts phase separation to inhibit global transcription after DNA damage
DNA damage shuts down genome-wide transcription to prevent transcriptional mutagenesis and to initiate repair signalling, but the mechanism to stall elongating RNA polymerase II (Pol II) is not fully understood. Central to the DNA damage response, poly(ADP-ribose) polymerase 1 (PARP1) initiates DNA repair by translocating to the lesions where it catalyses protein poly(ADP-ribosylation). Here we report that PARP1 inhibits Pol II elongation by inactivating the transcription elongation factor P-TEFb, a CDK9-cyclin T1 (CycT1) heterodimer. After sensing damage, the activated PARP1 binds to transcriptionally engaged P-TEFb and modifies CycT1 at multiple positions, including histidine residues that are rarely used as an acceptor site. This prevents CycT1 from undergoing liquid-liquid phase separation that is required for CDK9 to hyperphosphorylate Pol II and to stimulate elongation. Functionally, poly(ADP-ribosylation) of CycT1 promotes DNA repair and cell survival. Thus, the P-TEFb-PARP1 signalling plays a protective role in transcription quality control and genomic stability maintenance after DNA damage